Patent Publication Number: US-2021177041-A1

Title: Aerosol generation

Description:
PRIORITY CLAIM 
     The present application is a National Phase entry of PCT Application No. PCT/EP2019/070728, filed Jul. 31, 2019 which claims priority from GB Patent Application No. 1812498.2 filed Jul. 31, 2018, each of which is hereby fully incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to aerosol generation. 
     BACKGROUND 
     Smoking articles such as cigarettes, cigars and the like burn tobacco during use to create tobacco smoke. Alternatives to these types of articles release an inhalable aerosol or vapor by releasing compounds from a substrate material by heating without burning. These may be referred to as non-combustible smoking articles or aerosol generating assemblies. 
     One example of such a product is a heating device which release compounds by heating, but not burning, a solid aerosolizable material. This solid aerosolizable material may, in some cases, contain a tobacco material. The heating volatilizes at least one component of the material, typically forming an inhalable aerosol. These products may be referred to as heat-not-burn devices, tobacco heating devices or tobacco heating products. Various different arrangements for volatilizing at least one component of the solid aerosolizable material are known. 
     As another example, there are e-cigarette/tobacco heating product hybrid devices, also known as electronic tobacco hybrid devices. These hybrid devices contain a liquid source (which may or may not contain nicotine) which is vaporized by heating to produce an inhalable vapor or aerosol. The device additionally contains a solid aerosolizable material (which may or may not contain a tobacco material) and components of this material are entrained in the inhalable vapor or aerosol to produce the inhaled medium. 
     Some known aerosol generating include more than one heater, with each heater configured to heat different parts of the smokable material in use. This then allows the different parts of the smokable material to be heated at different times so as to provide longevity of aerosol formation over the use lifetime. 
     SUMMARY 
     According to a first aspect of the present disclosure, there is provided an aerosol generating article for use in an aerosol generating assembly, wherein the aerosol generating article comprises: 
     (i) a tubular substrate which comprises a first aerosol-forming composition, wherein the first aerosol-forming composition comprises an amorphous solid; and 
     (ii) a second aerosol-forming composition, wherein the second aerosol-forming composition is different from the first aerosol-forming composition. 
     A second aspect of the disclosure provides an aerosol generating assembly comprising an aerosol generating article according to the first aspect and a heater configured to heat but not burn at least one of the aerosol-forming compositions. 
     A further aspect of the disclosure provides a method of making a tubular substrate comprising (a) forming a slurry comprising components of the first aerosol-forming composition or precursors thereof, (b) applying the slurry to a sheet carrier, (c) setting the slurry to form a gel, (d) drying to form an amorphous solid, and (e) rolling to form a tube. 
     Further aspects of the disclosure described herein may provide the use of the aerosol generating article or the aerosol generating assembly, in the generation of an inhalable aerosol. 
     Further features and advantages of the disclosure will become apparent from the following description, given by way of example only, and with reference to the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows a section view of an example of an aerosol generating article. 
         FIG. 2  shows a perspective view of the article of  FIG. 1 . 
         FIG. 3  shows a sectional elevation of an example of an aerosol generating article. 
         FIG. 4  shows a perspective view of the article of  FIG. 3 . 
         FIG. 5  shows a perspective view of an example of an aerosol generating assembly. 
         FIG. 6  shows a section view of an example of an aerosol generating assembly. 
         FIG. 7  shows a perspective view of an example of an aerosol generating assembly. 
         FIG. 8  shows an example of a tubular substrate. 
         FIG. 9  shows another example of a tubular substrate. 
         FIG. 10  shows another example of a tubular substrate. 
     
    
    
     DETAILED DESCRIPTION 
     At least the first aerosol-forming composition described herein comprises an aerosol-forming material referred to as an “amorphous solid”. Any material described herein as an “amorphous solid” may alternatively be referred to as a “monolithic solid” (i.e. non-fibrous), or as a “dried gel”. The amorphous solid is a solid material that may retain some fluid, such as liquid, within it. Aerosol-forming materials described herein may, in some cases, comprise an amorphous solid in an amount from 50 wt %, 60 wt % or 70 wt %, to about 90 wt %, 95 wt % or 100 wt %. In some cases, the aerosol-forming material may consist of amorphous solid. 
     The disclosure provides an aerosol generating article for use in an aerosol generating assembly, wherein the article comprises: 
     (i) a tubular substrate which comprises a first aerosol-forming composition, wherein the first aerosol-forming composition comprises an amorphous solid; and 
     (ii) a second aerosol-forming composition, wherein the second aerosol-forming composition is different from the first aerosol-forming composition. 
     One or both of the aerosol-forming compositions are heated in use to generate an inhalable aerosol or vapor. The use of two or more aerosol-forming compositions allows the composition of the inhaled aerosol to be selectively tuned. The disclosure provides an amorphous solid as a component of the first aerosol-forming composition, and this solid may contain aerosolizable components (such as aerosol generating agents, flavorants, nicotine and nicotine derivatives and aromas). These amorphous solid-derived aerosolizable components are volatilized in use and inhaled; the provision of the amorphous solid allows the composition of the aerosol or vapor to be altered/enhanced. The amorphous solid typically comprises an active substance such as nicotine and/or a tobacco extract. 
     The inventors have established that in known aerosol generating assemblies, in which a uniform aerosol generating article is used, the delivery of components of the aerosol reduces over the use lifetime. In the present case, through providing two different aerosol-forming compositions which react differently to heat, and which may be exposed to different heat profiles, it is possible to alter the aerosol delivery profile. The delivery profile can be tuned, depending on what compositions and what heat profiles are used. 
     The tubular nature of the substrate may be adapted for use in a number of ways. In some cases, the aerosol generating article is configured for use with an aerosol generating assembly in which a heater is disposed inside the tube in use. In other cases, the aerosol generating article is configured for use with an aerosol generating assembly in which a heater is disposed outside of the tube in use. In such cases, it may be that no components of the aerosol generating assembly are arranged in the tube in use; rather, the tube provides a flow path for the aerosol or vapor in use; this may reduce or prevent condensation of the aerosol or vapor on reusable components of the aerosol generating assembly, thereby improving consumption efficiency and hygiene. In some such cases, the outside wall of the tube may be substantially or wholly impermeable to gas/aerosol, further controlling the flow path. 
     In some cases, the tubular substrate also comprises the second aerosol-forming composition. 
     In some cases, the second aerosol-forming composition comprises an amorphous solid. This may be a shredded sheet of amorphous solid and, in some cases, this may be disposed inside the tube of the tubular substrate. 
     In other cases, the second aerosol-forming composition comprises tobacco. In some cases, the tobacco is a reconstituted tobacco, optionally in cut-rag form. In some cases, the tobacco may be disposed inside the tube of the tubular substrate. 
     In some cases, the aerosol generating article has first and second sections wherein the amount of the first aerosol-forming composition and/or the amount of the second aerosol-forming compositions provided in first section is different to the respective amount provided in the second section. In such cases, the different sections may be subject to different heating profiles in use, thereby providing an inhalable aerosol in which the composition changes during the consumption period. That is, the different sections may be heated at different times or rates or to different temperatures, for example. In some cases, the first and second sections are spaced along length of the tube of the tubular substrate. In other cases, they may be arranged on opposing sides of the tubular substrate. 
     In some cases, substantially all of the first aerosol-forming composition may be provided in the first section and substantially all of the second aerosol-forming composition may be provided in the second section. In other cases, each section may comprise both the first and second aerosol-forming compositions. 
     In other cases, substantially all of the first and second aerosol-forming compositions may be subject to substantially the same heat profile. 
     In some specific examples, the tubular substrate comprises the first and second aerosol-forming compositions. These may each comprise an amorphous solid. In such cases, the amorphous solids may be provided as layers on the inside of the tubular substrate. In some cases, there may be sections of the tube that contain both aerosol-forming compositions, whilst there may be other sections that contain only one. The two compositions may be provided as two layers, such that one is provided on top of the other. The layer thicknesses may vary along the tube length or may be substantially the same. In a further alternative, the amorphous solids may be provided in different sections of the tubular substrate so that one is provided as a layer near to a mouth end and the second as a layer near to a distal end. In some cases, the amorphous solids may be provided as two co-axial tubes arranged end-to-end. In yet a further alternative, the amorphous solids may be provided as hemi-cylindrical layers on the inside of the tube. 
     Some other specific examples, in which the tubular substrate comprises the first and second aerosol-forming compositions, provide an aerosol generating article in which the first aerosol-forming composition comprises an amorphous solid and the second comprises tobacco. For example, the second aerosol-forming composition may comprise a sheet of reconstituted tobacco on which the first aerosol-forming composition is supported. In another example, the amorphous solid of the first aerosol-forming composition may be provided in a first section of the tube and a sheet of tobacco (of the second aerosol-forming composition) may be provided in a second section of the tube. In yet a further example, the sheet of tobacco may be arranged along the whole length of the tube, with an amorphous solid composition disposed on the tobacco sheet along only a portion of the tube. 
     In other specific examples, the second aerosol-forming composition may comprise tobacco, suitably in cut rag form. This may be a reconstituted tobacco. The tobacco may be provided inside the tube of the tubular substrate. In some cases, the tobacco may be provided in the same section of tube as the first aerosol-forming composition. In other cases, it may be provided in a different section of tube from the second aerosol-forming composition. In yet other examples, the tobacco composition may be provided in two sections of tube while the first aerosol-forming composition is provided in only one section. In yet further examples, the first aerosol-forming composition may be provided in two sections of tube while the tobacco composition is provided in only one section. 
     In one instance, the first aerosol-forming composition comprises an amorphous solid that comprises a flavorant and no tobacco material, and the second aerosol-forming composition comprises a tobacco material. 
     Generally, amorphous solid components of the tubular substrate will be arranged adjacent to the inside of the tube. In some cases, the outside surface of the tubular substrate tube may be circumscribed by a wrapper which is substantially or wholly impermeable to aerosol or vapor (to prevent passage of the formed aerosol or vapor to the tube exterior in use). This directs the inhaled components to the tube interior, and may prevent condensation of the components on reusable components of the aerosol generating assembly (thereby improving the consumption experience and hygiene). The wrapper may be formed from, for example, a metallic foil which conducts heat in use. 
     The tubular substrate comprises a first aerosol-forming composition which itself comprises an amorphous solid. The tubular substrate may accordingly be an amorphous solid sheet which has been rolled to form a tube. The substrate may comprise support members. Support members may be embedded in the amorphous solid, or may be a carrier on which the amorphous solid is provided. For example, the tubular substrate may comprise a carrier in the form of a sheet, which may be a sheet of metal foil or paper, or a laminate comprising metal foil or paper, on which the amorphous solid is provided. In some cases, the carrier comprises one or more materials selected from metal foil, paper, carbon paper, greaseproof paper, ceramic, carbon allotropes such as graphite and graphene, plastic, cardboard, wood, or combinations thereof. In some cases, the carrier may comprise or consist of a tobacco material, such as a sheet of reconstituted tobacco. In some cases, the carrier may be formed from materials selected from metal foil, paper, cardboard, wood or combinations thereof. In some cases, the carrier itself be a laminate structure comprising layers of materials selected from the preceding lists. The tubular substrate may be formed as a planar sheet and then rolled to form a tube. Alternatively, as described above, the carrier sheet may be a sheet comprising reconstituted tobacco which is the second aerosol-forming composition. 
     It may be preferable that a surface of the carrier sheet abutting the amorphous solid be formed from a porous material such as paper or reconstituted tobacco. This allows for a strong bond to form between the amorphous solid and porous carrier surface. The amorphous solid is formed by drying a gel and, without being limited by theory, it is thought that the slurry from which the gel is formed partially impregnates the porous layer so that when the gel sets and forms cross-links, the porous layer is partially bound into the gel. In some cases, the carrier comprises or consists of a paper sheet. The paper may have a porosity of 0-300 Coresta Units (CU), suitably 5-100 CU or 25-75 CU. 
     Additionally, surface roughness may contribute to the strength of bond between the amorphous material and the carrier. The inventors have found that the paper roughness (for the surface abutting the carrier) may suitably be in the range of 50-1000 Bekk seconds, suitably 50-150 Bekk seconds, suitably 100 Bekk seconds (measured over an air pressure interval of 50.66-48.00 kPa). (A Bekk smoothness tester is an instrument used to determine the smoothness of a paper surface, in which air at a specified pressure is leaked between a smooth glass surface and a paper sample, and the time (in seconds) for a fixed volume of air to seep between these surfaces is the “Bekk smoothness”.) 
     Conversely, the surface of the carrier facing away from the amorphous solid may be arranged in contact with the heater, and a smoother surface may provide more efficient heat transfer. Thus, in some cases, the carrier is disposed so as to have a rougher side abutting the amorphous material and a smoother side facing away from the amorphous material. 
     In some cases, one or more of the aerosol-forming compositions may comprise embedded heating means, such as resistive or inductive heating elements. For example, the heating means may be embedded in an amorphous solid. 
     In some cases, the carrier comprises or consists of a foil-paper laminate, with the paper abutting the gel on the inside of the tube thereby forming a strong bond, and the foil being arranged on the outside of the tube, preventing passage of the formed aerosol or vapor to the tube exterior in use. 
     In another case, the foil layer of the paper-backed foil abuts the amorphous solid. The foil is substantially impermeable, thereby preventing water provided in the amorphous solid to be absorbed into the paper which could weaken its structural integrity. 
     In some cases, the carrier is formed from or comprises metal foil, such as aluminum foil. A metallic carrier may allow for better conduction of thermal energy to the amorphous solid. Additionally, or alternatively, a metal foil may function as a susceptor in an induction heating system. In particular embodiments, the carrier comprises a metal foil layer and a support layer, such as cardboard. In these embodiments, the metal foil layer may have a thickness of less than 20 μm, such as from about 1 μm to about 10 μm, suitably about 5 μm. 
     The aerosol generating article may additionally comprise a cooling element and/or a filter. The cooling element, if present, may act or function to cool gaseous or aerosol components. In some cases, it may act to cool gaseous components such that they condense to form an aerosol. It may also act to space the very hot parts of the apparatus from the user. The filter, if present, may comprise any suitable filter known in the art such as a cellulose acetate plug. 
     In some cases, the cooling element and/or filter (where present) may be wrapped by a layer that at least partially extends over the tubular substrate. This layer may be the wrapper that comprises a carrier and an amorphous solid. 
     The aerosol generating article may additionally comprise ventilation apertures. These may be provided in the sidewall of the article. In some cases, the ventilation apertures may be provided in the filter and/or cooling element. These apertures may allow cool air to be drawn into the article during use, which can mix with the heated volatilized components thereby cooling the aerosol. 
     The ventilation enhances the generation of visible heated volatilized components from the article when it is heated in use. The heated volatilized components are made visible by the process of cooling the heated volatilized components such that supersaturation of the heated volatilizedvolatilised components occurs. The heated volatilized components then undergo droplet formation, otherwise known as nucleation, and eventually the size of the aerosol particles of the heated volatilized components increases by further condensation of the heated volatilized components and by coagulation of newly formed droplets from the heated volatilized components. 
     In some cases, the ratio of the cool air to the sum of the heated volatilized components and the cool air, known as the ventilation ratio, is at least 15%. A ventilation ratio of 15% enables the heated volatilized components to be made visible by the method described above. The visibility of the heated volatilized components enables the user to identify that the volatilized components have been generated and adds to the sensory experience of the smoking experience. 
     In another example, the ventilation ratio is between 50% and 85% to provide additional cooling to the heated volatilized components. In some cases, the ventilation ratio may be at least 60% or 65%. 
     A second aspect of the disclosure provides an aerosol generating assembly comprising an aerosol generating article according to the first aspect and a heater configured to heat but not burn at least one of the aerosol-forming compositions. 
     In some cases, the heater may heat, without burning, the aerosolizable material to between 120° C. and 350° C. in use. In some cases, the heater may heat, without burning, the aerosolizable material to between 140° C. and 250° C. in use. In some cases in use, substantially all of the amorphous solid is less than about 4 mm, 3 mm, 2 mm or 1 mm from the heater. In some cases, the solid is disposed between about 0.010 mm and 2.0 mm from the heater, suitably between about 0.02 mm and 1.0 mm, suitably 0.1 mm to 0.5 mm. These minimum distances may, in some cases, reflect the thickness of a carrier that supports the amorphous solid. In some cases, a surface of the amorphous solid may directly abut the heater. 
     In some cases, the aerosol generating assembly contains an aerosol generating article in which the article has first and second sections which are spaced along length of the tube of the tubular substrate, and wherein the amount of the first aerosol-forming composition and/or the amount of the second aerosol-forming compositions provided in first section is different to the respective amount provided in the second section, and wherein the device is configured to provide a different heat profile to each of the first and second sections. 
     In some cases, heating of the first section of the aerosol generating article is initiated at a different time to heating of the second section. 
     For example, in some particular cases, an assembly is provided which is configured to heat the at least two sections of the aerosol generating article separately. By controlling the temperature of the first and second sections over time such that the temperature profiles of the sections are different, it is possible to control the puff profile of the aerosol during use. The heat provided to the two sections of the aerosol generating article may be provided at different times or rates; staggering the heating in this way may allow for both fast aerosol production and longevity of use. 
     In one particular example, the assembly may be configured such that on initiation of the consumption experience, a first heating element corresponding to a first section of the aerosol generating article is immediately heated to a temperature of 240° C. This first heating element is maintained at 240° C. for 145 seconds and then drops to 135° C. (where it remains for the rest of the consumption experience). 75 seconds after initiation of the consumption experience, a second heating element corresponding to a second section of the aerosol generating article is heated to a temperature of 160° C. 135 seconds after initiation of the consumption experience, the temperature of the second heating element is raised to 240° C. (where it remains for the rest of the consumption experience). The consumption experience lasts 280 seconds, at which point both heaters are cool to room temperature. 
     In some cases, the device is configured such that the user controls initiation of heating of the respective sections, allowing the consumer to control the consumption experience. 
     In some cases, the aerosol generating assembly may comprise at least two heaters, wherein the heaters are arranged to respectively heat, without burning, different sections of the aerosol generating article. 
     In some cases, the aerosol generating assembly may be configured such that the heater is disposed inside the tube of the tubular substrate. 
     In some cases, the aerosol generating assembly is configured such that the heater is disposed outside the tube of the tubular substrate. In some cases, the aerosol generating assembly is configured such that no components of the aerosol generating assembly are disposed inside the tube of the tubular substrate in use. The tube is vacant in use and may provide a flow path for the inhalable aerosol/gas. 
     In some cases, the aerosol generating assembly may be a heat-not-burn device. That is, it may contain a solid tobacco-containing material (and no liquid aerosolizable material). In some cases, the amorphous solid may comprise the tobacco material. A heat-not-burn device is disclosed in WO 2015/062983 A2, which is incorporated by reference in its entirety. 
     In some cases, the aerosol generating assembly may be an electronic tobacco hybrid device. That is, it may contain a solid aerosolizable material and a liquid aerosolizable material. In some cases, the amorphous solid may comprise nicotine. In some cases, the amorphous solid may comprise a tobacco material. In some cases, the amorphous solid may comprise a tobacco material and a separate nicotine source. The separate aerosolizable materials may be heated by separate heaters, the same heater or, in one case, a downstream aerosolizable material may be heated by a hot aerosol which is generated from the upstream aerosolizable material. An electronic tobacco hybrid device is disclosed in WO 2016/135331 A1, which is incorporated by reference in its entirety. 
     The heater provided in assemblies according to the second aspect may be, in some cases, a thin film, electrically resistive heater. In other cases, the heater may comprise an induction heater or the like. The heater may be a combustible heat source or a chemical heat source which undergoes an exothermic reaction to product heat in use. The aerosol generating assembly may comprise a plurality of heaters. The heater(s) may be connected to a battery. Where more than one heater is present, each heater may be the same or different. 
     Generally, the or each heater is powered by a battery, which may be a rechargeable battery or a non-rechargeable battery. Examples of suitable batteries include for example a lithium-ion battery, a nickel battery (such as a nickel-cadmium battery), an alkaline battery and/or the like. The battery is electrically coupled to the heater to supply electrical power when required to heat the smokable material (to volatilize components of the smokable material without causing the smokable material to burn). 
     In one example, the heater is generally in the form of a hollow cylindrical tube, having a hollow interior heating chamber into which the aerosol generating article is inserted for heating in use. Different arrangements for the heater are possible. For example, the heater may be formed as a single heater or may be formed of plural heaters aligned along the longitudinal axis of the aerosol generating article. (For simplicity, reference to a “heater” herein shall be taken to include plural heaters, unless the context requires otherwise.) The heater may be annular or tubular. The heater may be is dimensioned so that substantially the whole of the aerosol generating article material when inserted is located within the heating element(s) of the heater so that substantially the whole of the aerosolizable material is heated in use. The heater may be arranged so that selected zones of the aerosolizable material can be independently heated, for example in turn (sequentially) or together (simultaneously) as desired. 
     In another example, the heater may be rod-shaped and the assembly may be configured such that the heater is at least partially inside the tubular substrate in use. 
     The heater may be surrounded along at least part of its length by a thermal insulator which helps to reduce heat passing from the heater to the exterior of the aerosol generating assembly. This helps to keep down the power requirements for the heater as it reduces heat losses generally. The insulator also helps to keep the exterior of the aerosol generating assembly cool during operation of the heater. 
     Referring to  FIGS. 1 and 2 , there are shown a partially cut-away section view and a perspective view of an example of an aerosol generating article  101 . The article  101  is adapted for use with a device having a power source and a heater. The article  101  of this embodiment is particularly suitable for use with the device  51  shown in  FIGS. 5 to 7 , described below. In use, the article  101  may be removably inserted into the device shown in  FIG. 5  at an insertion point  20  of the device  51 . 
     The article  101  of one example is in the form of a substantially cylindrical rod that includes a tubular substrate  103  as defined herein and a filter assembly  105  in the form of a rod. The tubular substrate  103  is also illustrated in  FIG. 8  and comprises two aerosol-forming amorphous solid compositions  103   a ,  103   b  in sections  104  and  106 . Each amorphous solid composition is in the form of a tube and they are arranged end to end (i.e. coaxially arranged but relatively displaced along that axis). The amorphous solid section  103   b  is closer to the filter assembly  105  than the amorphous solid section  103   a . The tubular substrate of  FIG. 8  is shown in aerosol forming articles  101 ,  301  in  FIGS. 1 to 4 , but in other embodiments, the substrate  103 ,  303  in these articles may have a different form, such as but not limited to, the forms shown in  FIGS. 9 and 10 . 
     In  FIG. 9 , the tubular substrate  903  comprises two aerosol-forming amorphous solid compositions  903   a  and  903   b . The substrate  903  comprises two sections  904  and  906 , each of which comprises a different amount of the respective amorphous solids  903   a  and  903   b . The sections may be subject to different heat profiles in use, providing an inhalable aerosol that changes in composition over the product lifetime. 
     In  FIG. 10 , the tubular substrate  1003  comprises a first aerosol-forming composition in the form of an amorphous solid tube  1003   a  and a section aerosol-forming composition  1003   b  in the form of cut rag tobacco disposed inside the tube. As for the substrates  103  and  903  illustrated in  FIGS. 8 and 9 , it can be seen that the two sections  1004  and  1006  of the tubular substrate  1003 , each contain a different amount of aerosol-forming material. The sections may be subject to different heat profiles in use, providing an inhalable aerosol that changes in composition over the product lifetime. 
     The filter assembly  105  includes three segments, a cooling segment  107 , a filter segment  109  and a mouth end segment  111 . The article  101  has a first end  113 , also known as a mouth end or a proximal end and a second end  115 , also known as a distal end. The tubular substrate  103  is located towards the distal end  115  of the article  101 . In one example, the cooling segment  107  is located adjacent to the tubular substrate  103  between the tubular substrate  103  and the filter segment  109 , such that the cooling segment  107  is in an abutting relationship with the tubular substrate  103  and the filter segment  103 . In other examples, there may be a separation between the tubular substrate  103  and the cooling segment  107  and between the tubular substrate  103  and the filter segment  109 . The filter segment  109  is located in between the cooling segment  107  and the mouth end segment  111 . The mouth end segment  111  is located towards the proximal end  113  of the article  101 , adjacent the filter segment  109 . In one example, the filter segment  109  is in an abutting relationship with the mouth end segment  111 . In one embodiment, the total length of the filter assembly  105  is between 37 mm and 45 mm, more preferably, the total length of the filter assembly  105  is 41 mm. 
     In one example, the tubular substrate  103  is between 34 mm and 50 mm in length, suitably between 38 mm and 46 mm in length, suitably 42 mm in length. 
     In one example, the total length of the article  101  is between 71 mm and 95 mm, suitably between 79 mm and 87 mm, suitably 83 mm. 
     The tubular substrate  103  is joined to the filter assembly  105  by annular tipping paper (not shown), which is located substantially around the circumference of the filter assembly  105  to surround the filter assembly  105  and extends partially along the length of the tubular substrate  103 . In one example, the tipping paper is made of 58GSM standard tipping base paper. In one example the tipping paper has a length of between 42 mm and 50 mm, suitably of 46 mm. 
     In one example, the cooling segment  107  is an annular tube and is located around and defines an air gap within the cooling segment. The air gap provides a chamber for heated volatilized components generated from the tubular substrate  103  to flow. The cooling segment  107  is hollow to provide a chamber for aerosol accumulation yet rigid enough to withstand axial compressive forces and bending moments that might arise during manufacture and whilst the article  101  is in use during insertion into the device  51 . In one example, the thickness of the wall of the cooling segment  107  is approximately 0.29 mm. 
     The cooling segment  107  provides a physical displacement between the tubular substrate  103  and the filter segment  109 . The physical displacement provided by the cooling segment  107  will provide a thermal gradient across the length of the cooling segment  107 . In one example the cooling segment  107  is configured to provide a temperature differential of at least 40 degrees Celsius between a heated volatilized component entering a first end of the cooling segment  107  and a heated volatilized component exiting a second end of the cooling segment  107 . In one example the cooling segment  107  is configured to provide a temperature differential of at least 60 degrees Celsius between a heated volatilized component entering a first end of the cooling segment  107  and a heated volatilized component exiting a second end of the cooling segment  107 . This temperature differential across the length of the cooling element  107  protects the temperature sensitive filter segment  109  from the high temperatures of the tubular substrate  103  when it is heated by the device  51 . If the physical displacement was not provided between the filter segment  109  and the tubular substrate  103  and the heating elements of the device  51 , then the temperature sensitive filter segment may  109  become damaged in use, so it would not perform its required functions as effectively. 
     In one example the length of the cooling segment  107  is at least 15 mm. In one example, the length of the cooling segment  107  is between 20 mm and 30 mm, more particularly 23 mm to 27 mm, more particularly 25 mm to 27 mm, suitably 25 mm. 
     The cooling segment  107  is made of paper, which means that it is comprised of a material that does not generate compounds of concern, for example, toxic compounds when in use adjacent to the heater of the device  51 . In one example, the cooling segment  107  is manufactured from a spirally wound paper tube which provides a hollow internal chamber yet maintains mechanical rigidity. Spirally wound paper tubes are able to meet the tight dimensional accuracy requirements of high-speed manufacturing processes with respect to tube length, outer diameter, roundness and straightness. 
     In another example, the cooling segment  107  is a recess created from stiff plug wrap or tipping paper. The stiff plug wrap or tipping paper is manufactured to have a rigidity that is sufficient to withstand the axial compressive forces and bending moments that might arise during manufacture and whilst the article  101  is in use during insertion into the device  51 . 
     The filter segment  109  may be formed of any filter material sufficient to remove one or more volatilized compounds from heated volatilized components from the tubular substrate. In one example the filter segment  109  is made of a mono-acetate material, such as cellulose acetate. The filter segment  109  provides cooling and irritation-reduction from the heated volatilized components without depleting the quantity of the heated volatilized components to an unsatisfactory level for a user. 
     In some embodiments, a capsule (not illustrated) may be provided in filter segment  109 . It may be disposed substantially centrally in the filter segment  109 , both across the filter segment  109  diameter and along the filter segment  109  length. In other cases, it may be offset in one or more dimension. The capsule may in some cases, where present, contain a volatile component such as a flavorant or aerosol generating agent. 
     The density of the cellulose acetate tow material of the filter segment  109  controls the pressure drop across the filter segment  109 , which in turn controls the draw resistance of the article  101 . Therefore the selection of the material of the filter segment  109  is important in controlling the resistance to draw of the article  101 . In addition, the filter segment performs a filtration function in the article  101 . 
     In one example, the filter segment  109  is made of a 8Y15 grade of filter tow material, which provides a filtration effect on the heated volatilized material, whilst also reducing the size of condensed aerosol droplets which result from the heated volatilized material. 
     The presence of the filter segment  109  provides an insulating effect by providing further cooling to the heated volatilized components that exit the cooling segment  107 . This further cooling effect reduces the contact temperature of the user&#39;s lips on the surface of the filter segment  109 . 
     In one example, the filter segment  109  is between 6 mm to 10 mm in length, suitably 8 mm. 
     The mouth end segment  111  is an annular tube and is located around and defines an air gap within the mouth end segment  111 . The air gap provides a chamber for heated volatilized components that flow from the filter segment  109 . The mouth end segment  111  is hollow to provide a chamber for aerosol accumulation yet rigid enough to withstand axial compressive forces and bending moments that might arise during manufacture and whilst the article is in use during insertion into the device  51 . In one example, the thickness of the wall of the mouth end segment  111  is approximately 0.29 mm. In one example, the length of the mouth end segment  111  is between 6 mm to 10 mm, suitably 8 mm. 
     The mouth end segment  111  may be manufactured from a spirally wound paper tube which provides a hollow internal chamber yet maintains critical mechanical rigidity. Spirally wound paper tubes are able to meet the tight dimensional accuracy requirements of high-speed manufacturing processes with respect to tube length, outer diameter, roundness and straightness. 
     The mouth end segment  111  provides the function of preventing any liquid condensate that accumulates at the exit of the filter segment  109  from coming into direct contact with a user. 
     It should be appreciated that, in one example, the mouth end segment  111  and the cooling segment  107  may be formed of a single tube and the filter segment  109  is located within that tube separating the mouth end segment  111  and the cooling segment  107 . 
     Referring to  FIGS. 3 and 4 , there are shown a partially cut-away section and perspective views of an example of an article  301 . The reference signs shown in  FIGS. 3 and 4  are equivalent to the reference signs shown in  FIGS. 1 and 2 , but with an increment of 200. 
     In the example of the article  301  shown in  FIGS. 3 and 4 , a ventilation region  317  is provided in the article  301  to enable air to flow into the interior of the article  301  from the exterior of the article  301 . In one example the ventilation region  317  takes the form of one or more ventilation holes  317  formed through the outer layer of the article  301 . The ventilation holes may be located in the cooling segment  307  to aid with the cooling of the article  301 . In one example, the ventilation region  317  comprises one or more rows of holes, and preferably, each row of holes is arranged circumferentially around the article  301  in a cross-section that is substantially perpendicular to a longitudinal axis of the article  301 . 
     In one example, there are between one to four rows of ventilation holes to provide ventilation for the article  301 . Each row of ventilation holes may have between 12 to 36 ventilation holes  317 . The ventilation holes  317  may, for example, be between 100 to 500 μm in diameter. In one example, an axial separation between rows of ventilation holes  317  is between 0.25 mm and 0.75 mm, suitably 0.5 mm. 
     In one example, the ventilation holes  317  are of uniform size. In another example, the ventilation holes  317  vary in size. The ventilation holes can be made using any suitable technique, for example, one or more of the following techniques: laser technology, mechanical perforation of the cooling segment  307  or pre-perforation of the cooling segment  307  before it is formed into the article  301 . The ventilation holes  317  are positioned so as to provide effective cooling to the article  301 . 
     In one example, the rows of ventilation holes  317  are located at least 11 mm from the proximal end  313  of the article, suitably between 17 mm and 20 mm from the proximal end  313  of the article  301 . The location of the ventilation holes  317  is positioned such that user does not block the ventilation holes  317  when the article  301  is in use. 
     Providing the rows of ventilation holes between 17 mm and 20 mm from the proximal end  313  of the article  301  enables the ventilation holes  317  to be located outside of the device  51 , when the article  301  is fully inserted in the device  51 , as can be seen in  FIGS. 6 and 7 . By locating the ventilation holes outside of the device, non-heated air is able to enter the article  301  through the ventilation holes from outside the device  51  to aid with the cooling of the article  301 . 
     The length of the cooling segment  307  is such that the cooling segment  307  will be partially inserted into the device  51 , when the article  301  is fully inserted into the device  51 . The length of the cooling segment  307  provides a first function of providing a physical gap between the heater arrangement of the device  51  and the heat sensitive filter arrangement  309 , and a second function of enabling the ventilation holes  317  to be located in the cooling segment, whilst also being located outside of the device  51 , when the article  301  is fully inserted into the device  51 . As can be seen from  FIGS. 6 and 7 , the majority of the cooling element  307  is located within the device  51 . However, there is a portion of the cooling element  307  that extends out of the device  51 . It is in this portion of the cooling element  307  that extends out of the device  51  in which the ventilation holes  317  are located. 
     Referring now to  FIGS. 5 to 7  in more detail, there is shown an example of a device  51  arranged to heat an aerosol generating material to volatilize at least one component of said aerosol generating material, typically to form an aerosol which can be inhaled. The device  51  is a heating device which releases compounds by heating, but not burning, the aerosol generating material. 
     A first end  53  is sometimes referred to herein as the mouth or proximal end  53  of the device  51  and a second end  55  is sometimes referred to herein as the distal end  55  of the device  51 . The device  51  has an on/off button  57  to allow the device  51  as a whole to be switched on and off as desired by a user. 
     The device  51  comprises a housing  59  for locating and protecting various internal components of the device  51 . In the example shown, the housing  59  comprises a uni-body sleeve  11  that encompasses the perimeter of the device  51 , capped with a top panel  17  which defines generally the ‘top’ of the device  51  and a bottom panel  19  which defines generally the ‘bottom’ of the device  51 . In another example the housing comprises a front panel, a rear panel and a pair of opposite side panels in addition to the top panel  17  and the bottom panel  19 . 
     The top panel  17  and/or the bottom panel  19  may be removably fixed to the uni-body sleeve  11 , to permit easy access to the interior of the device  51 , or may be “permanently” fixed to the uni-body sleeve  11 , for example to deter a user from accessing the interior of the device  51 . In an example, the panels  17  and  19  are made of a plastics material, including for example glass-filled nylon formed by injection molding, and the uni-body sleeve  11  is made of aluminum, though other materials and other manufacturing processes may be used. 
     The top panel  17  of the device  51  has an opening  20  at the mouth end  53  of the device  51  through which, in use, the article  101 ,  301  including the tubular substrate may be inserted into the device  51  and removed from the device  51  by a user. 
     The housing  59  has located or fixed therein a heater arrangement  23 , control circuitry  25  and a power source  27 . In this example, the heater arrangement  23 , the control circuitry  25  and the power source  27  are laterally adjacent (that is, adjacent when viewed from an end), with the control circuitry  25  being located generally between the heater arrangement  23  and the power source  27 , though other locations are possible. 
     The control circuitry  25  may include a controller, such as a microprocessor arrangement, configured and arranged to control the heating of the tubular substrate in the article  101 ,  301  as discussed further below. 
     The power source  27  may be for example a battery, which may be a rechargeable battery or a non-rechargeable battery. Examples of suitable batteries include for example a lithium-ion battery, a nickel battery (such as a nickel-cadmium battery), an alkaline battery and/or the like. The battery  27  is electrically coupled to the heater arrangement  23  to supply electrical power when required and under control of the control circuitry  25  to heat the tubular substrate in the article (as discussed, to volatilize the aerosol-forming compositions without causing them to burn). 
     An advantage of locating the power source  27  laterally adjacent to the heater arrangement  23  is that a physically large power source  25  may be used without causing the device  51  as a whole to be unduly lengthy. As will be understood, in general a physically large power source  25  has a higher capacity (that is, the total electrical energy that can be supplied, often measured in Amp-hours or the like) and thus the battery life for the device  51  can be longer. 
     In one example, the heater arrangement  23  is generally in the form of a hollow cylindrical tube, having a hollow interior heating chamber  29  into which the article  101 ,  301  comprising the tubular substrate is inserted for heating in use. In the illustrated assembly, no components of the heater arrangement are inserted into the hollow tube of the tubular substrate  103 ,  303 . (Indeed, no components of the device  51  are inserted into the hollow tube of the tubular substrate  103 ,  303 ). Different arrangements for the heater arrangement  23  are possible. For example, the heater arrangement  23  may comprise a single heating element or may be formed of plural heating elements aligned along the longitudinal axis of the heater arrangement  23 . The or each heating element may be annular or tubular, or at least part-annular or part-tubular around its circumference. In an example, the or each heating element may be a thin film heater. In another example, the or each heating element may be made of a ceramics material. Examples of suitable ceramics materials include alumina and aluminum nitride and silicon nitride ceramics, which may be laminated and sintered. Other heating arrangements are possible, including for example inductive heating, infrared heater elements, which heat by emitting infrared radiation, or resistive heating elements formed by for example a resistive electrical winding. In another example (not illustrated), the heater may be in the form of a blade or rod which is inserted into the hollow tube of the tubular substrate  103 ,  303 . 
     In one particular example, the heater arrangement  23  is supported by a stainless steel support tube and comprises a polyimide heating element. The heater arrangement  23  is dimensioned so that substantially the whole of the tubular substrate  103 ,  303  of the article  101 ,  301  is inserted into the heater arrangement  23  when the article  101 ,  301  is inserted into the device  51 . 
     The or each heating element may be arranged so that selected zones of the tubular substrate can be independently heated, for example in turn (over time, as discussed above) or together (simultaneously) as desired. 
     The heater arrangement  23  in this example is surrounded along at least part of its length by a thermal insulator  31 . The insulator  31  helps to reduce heat passing from the heater arrangement  23  to the exterior of the device  51 . This helps to keep down the power requirements for the heater arrangement  23  as it reduces heat losses generally. The insulator  31  also helps to keep the exterior of the device  51  cool during operation of the heater arrangement  23 . In one example, the insulator  31  may be a double-walled sleeve which provides a low pressure region between the two walls of the sleeve. That is, the insulator  31  may be for example a “vacuum” tube, i.e. a tube that has been at least partially evacuated so as to minimize heat transfer by conduction and/or convection. Other arrangements for the insulator  31  are possible, including using heat insulating materials, including for example a suitable foam-type material, in addition to or instead of a double-walled sleeve. 
     The housing  59  may further comprises various internal support structures  37  for supporting all internal components, as well as the heating arrangement  23 . 
     The device  51  further comprises a collar  33  which extends around and projects from the opening  20  into the interior of the housing  59  and a generally tubular chamber  35  which is located between the collar  33  and one end of the vacuum sleeve  31 . The chamber  35  further comprises a cooling structure  35   f , which in this example, comprises a plurality of cooling fins  35   f  spaced apart along the outer surface of the chamber  35 , and each arranged circumferentially around outer surface of the chamber  35 . There is an air gap  36  between the hollow chamber  35  and the article  101 ,  301  when it is inserted in the device  51  over at least part of the length of the hollow chamber  35 . The air gap  36  is around all of the circumference of the article  101 ,  301  over at least part of the cooling segment  307 . 
     The collar  33  comprises a plurality of ridges  60  arranged circumferentially around the periphery of the opening  20  and which project into the opening  20 . The ridges  60  take up space within the opening  20  such that the open span of the opening  20  at the locations of the ridges  60  is less than the open span of the opening  20  at the locations without the ridges  60 . The ridges  60  are configured to engage with an article  101 ,  301  inserted into the device to assist in securing it within the device  51 . Open spaces (not shown in the Figures) defined by adjacent pairs of ridges  60  and the article  101 ,  301  form ventilation paths around the exterior of the article  101 ,  301 . These ventilation paths allow hot vapors that have escaped from the article  101 ,  301  to exit the device  51  and allow cooling air to flow into the device  51  around the article  101 ,  301  in the air gap  36 . 
     In operation, the article  101 ,  301  is removably inserted into an insertion point  20  of the device  51 , as shown in  FIGS. 5 to 7 . Referring particularly to  FIG. 6 , in one example, the tubular substrate  103 ,  303 , which is located towards the distal end  115 ,  315  of the article  101 ,  301 , is entirely received within the heater arrangement  23  of the device  51 . The proximal end  113 ,  313  of the article  101 ,  301  extends from the device  51  and acts as a mouthpiece assembly for a user. 
     In operation, the heater arrangement  23  will heat the article  101 ,  301  to volatilize at least one component of the aerosol-forming compositions from the tubular substrate  103 ,  303 . 
     The primary flow path for the heated volatilized components from the tubular substrate  103 ,  303  is axially through the article  101 ,  301 . In examples, such as that illustrated in  FIGS. 5 to 7 , where no component of the device  51  is arranged inside the hollow tube of the tubular substrate  103 ,  303  in use, the heated volatilized components from the tubular substrate flow through the hollow tube. The heated volatilized components then flow through the chamber inside the cooling segment  107 ,  307 , through the filter segment  109 ,  309 , through the mouth end segment  111 ,  313  to the user. 
     In one example, the temperature of the heated volatilized components that are generated from the tubular substrate is between 60° C. and 250° C., which may be above the acceptable inhalation temperature for a user. As the heated volatilized component travels through the cooling segment  107 ,  307 , it will cool and some volatilized components will condense on the inner surface of the cooling segment  107 ,  307 . 
     In the examples of the article  301  shown in  FIGS. 3 and 4 , cool air will be able to enter the cooling segment  307  via the ventilation holes  317  formed in the cooling segment  307 . This cool air will mix with the heated volatilized components to provide additional cooling to the heated volatilized components. 
     Aerosol-Forming Material 
     In some cases, the amorphous solid may have a thickness of about 0.015 mm to about 1.0 mm. Suitably, the thickness may be in the range of about 0.05 mm, 0.1 mm or 0.15 mm to about 0.5 mm or 0.3 mm. The inventors have found that a material having a thickness of 0.2 mm is particularly suitable. The amorphous solid may comprise more than one layer, and the thickness described herein refers to the aggregate thickness of those layers. 
     The inventors have established that if the aerosol-forming amorphous solid is too thick, then heating efficiency is compromised. This adversely affects the power consumption in use. Conversely, if the aerosol-forming amorphous solid is too thin, it is difficult to manufacture and handle; a very thin material is harder to cast and may be fragile, compromising aerosol formation in use. 
     The inventors have established that the amorphous solid thicknesses stipulated herein optimize the material properties in view of these competing considerations. 
     The thickness stipulated herein is a mean thickness for the material. In some cases, the amorphous solid thickness may vary by no more than 25%, 20%, 15%, 10%, 5% or 1%. 
     In some cases, the amorphous solid may comprise 1-60 wt % of a gelling agent wherein these weights are calculated on a dry weight basis. 
     Suitably, the amorphous solid may comprise from about 1 wt %, 5 wt %, 10 wt %, 15 wt %, 20 wt % or 25 wt % to about 60 wt %, 50 wt %, 45 wt %, 40 wt %, 35 wt %, 30 wt % or 27 wt % of a gelling agent (all calculated on a dry weight basis). For example, the amorphous solid may comprise 1-50 wt %, 5-40 wt %, 10-30 wt % or 15-27 wt % of a gelling agent. 
     Suitably, the amorphous solid may comprise from about 1 wt %, 5 wt %, 10 wt %, 15 wt %, 20 wt % or 25 wt % to about 50 wt %, 45 wt %, 40 wt %, 35 wt %, 30 wt % or 27 wt % of a gelling agent (all calculated on a dry weight basis). For example, the amorphous solid may comprise 5-40 wt %, 10-30 wt % or 15-27 wt % of a gelling agent. 
     In some embodiments, the gelling agent comprises a hydrocolloid. In some embodiments, the gelling agent comprises one or more compounds selected from the group comprising alginates, pectins, starches (and derivatives), celluloses (and derivatives), gums, silica or silicones compounds, clays, polyvinyl alcohol and combinations thereof. For example, in some embodiments, the gelling agent comprises one or more of alginates, pectins, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethylcellulose, pullulan, xanthan gum guar gum, carrageenan, agarose, acacia gum, fumed silica, PDMS, sodium silicate, kaolin and polyvinyl alcohol. In some cases, the gelling agent comprises alginate and/or pectin, and may be combined with a setting agent (such as a calcium source) during formation of the amorphous solid. In some cases, the amorphous solid may comprise a calcium-crosslinked alginate and/or a calcium-crosslinked pectin. 
     In some embodiments, the gelling agent comprises alginate, and the alginate is present in the amorphous solid in an amount of from 10-30 wt % of the amorphous solid (calculated on a dry weight basis). In some embodiments, alginate is the only gelling agent present in the amorphous solid. In other embodiments, the gelling agent comprises alginate and at least one further gelling agent, such as pectin. 
     In some embodiments the amorphous solid may include gelling agent comprising carrageenan. 
     Suitably, the amorphous solid may comprise from about 5 wt %, 10 wt %, 15 wt %, or 20 wt % to about 80 wt %, 70 wt %, 60 wt %, 55 wt %, 50 wt %, 45 wt % 40 wt %, or 35 wt % of an aerosol generating agent (all calculated on a dry weight basis). The aerosol generating agent may act as a plasticizer. For example, the amorphous solid may comprise 5-60 wt %, 10-50 wt % or 20-40 wt % of an aerosol generating agent. In some cases, the aerosol generating agent comprises one or more compound selected from erythritol, propylene glycol, glycerol, triacetin, sorbitol and xylitol. In some cases, the aerosol generating agent comprises, consists essentially of or consists of glycerol. The inventors have established that if the content of the plasticizer is too high, the amorphous solid may absorb water resulting in a material that does not create an appropriate consumption experience in use. The inventors have established that if the plasticizer content is too low, the amorphous solid may be brittle and easily broken. The plasticizer content specified herein provides an amorphous solid flexibility which allows the amorphous solid sheet to be wound onto a bobbin, which is useful in manufacture of aerosol generating articles. 
     In some cases, the amorphous solid may comprise a flavor. Suitably, the amorphous solid may comprise up to about 60 wt %, 50 wt %, 40 wt %, 30 wt %, 20 wt %, 10 wt % or 5 wt % of a flavor. In some cases, the amorphous solid may comprise at least about 0.5 wt %, 1 wt %, 2 wt %, 5 wt % 10 wt %, 20 wt % or 30 wt % of a flavor (all calculated on a dry weight basis). For example, the amorphous solid may comprise 0.1-60 wt %, 1-60 wt %, 5-60 wt %, 10-60 wt %, 20-50 wt % or 30-40 wt % of a flavor. In some cases, the flavor (if present) comprises, consists essentially of or consists of menthol. In some cases, the amorphous solid does not comprise a flavorflavour. 
     In some cases, the amorphous solid additionally comprises an active substance. For example, in some cases, the amorphous solid additionally comprises a tobacco material and/or nicotine. For example, the amorphous solid may additionally comprise powdered tobacco and/or nicotine and/or a tobacco extract. In some cases, the amorphous solid may comprise from about 1 wt %, 5 wt %, 10 wt %, 15 wt %, 20 wt % or 25 wt % to about 70 wt %, 50 wt %, 45 wt % or 40 wt % (calculated on a dry weight basis) of active substance. In some cases, the amorphous solid may comprise from about 1 wt %, 5 wt %, 10 wt %, 15 wt %, 20 wt % or 25 wt % to about 70 wt %, 60 wt %, 50 wt %, 45 wt % or 40 wt % (calculated on a dry weight basis) of a tobacco material and/or nicotine. 
     In some cases, the amorphous solid comprises an active substance such as tobacco extract. In some cases, the amorphous solid may comprise 5-60 wt % (calculated on a dry weight basis) of tobacco extract. In some cases, the amorphous solid may comprise from about 5 wt %, 10 wt %, 15 wt %, 20 wt % or 25 wt % to about 55 wt %, 50 wt %, 45 wt % or 40 wt % (calculated on a dry weight basis) tobacco extract. For example, the amorphous solid may comprise 5-60 wt %, 10-55 wt % or 25-55 wt % of tobacco extract. The tobacco extract may contain nicotine at a concentration such that the amorphous solid comprises 1 wt % 1.5 wt %, 2 wt % or 2.5 wt % to about 6 wt %, 5 wt %, 4.5 wt % or 4 wt % (calculated on a dry weight basis) of nicotine. In some cases, there may be no nicotine in the amorphous solid other than that which results from the tobacco extract. 
     In some embodiments the amorphous solid comprises no tobacco material but does comprise nicotine. In some such cases, the amorphous solid may comprise from about 1 wt %, 2 wt %, 3 wt % or 4 wt % to about 20 wt %, 15 wt %, 10 wt % or 5 wt % (calculated on a dry weight basis) of nicotine. For example, the amorphous solid may comprise 1-20 wt % or 2-5 wt % of nicotine. 
     In some cases, the total content of active substance and/or flavor may be at least about 0.1 wt %, 1 wt %, 5 wt %, 10 wt %, 20 wt %, 25 wt % or 30 wt %. In some cases, the total content of active substance and/or flavor may be less than about 80 wt %, 70 wt %, 60 wt %, 50 wt % or 40 wt % (all calculated on a dry weight basis). 
     In some cases, the total content of tobacco material, nicotine and flavor may be at least about 0.1 wt %, 1 wt %, 5 wt %, 10 wt %, 20 wt %, 25 wt % or 30 wt %. In some cases, the total content of tobacco material, nicotine and flavor may be less than about, 80 wt %, 70 wt %, 60 wt %, 50 wt % or 40 wt % (all calculated on a dry weight basis). 
     In some embodiments, the amorphous solid is a hydrogel and comprises less than about 20 wt % of water calculated on a wet weight basis. In some cases, the hydrogel may comprise less than about 15 wt %, 12 wt % or 10 wt % of water calculated on a wet weight basis (WWB). In some cases, the hydrogel may comprise at least about 1 wt %, 2 wt % or at least about 5 wt % of water (WWB). In some cases, the amorphous solid comprises from about 1 wt % to about 15 wt % water, or from about 5 wt % to about 15 wt % calculated on a wet weight basis. Suitably, the water content of the amorphous solid may be from about 5 wt %, 7 wt % or 9 wt % to about 15 wt %, 13 wt % or 11 wt % (WWB), most suitably about 10 wt %. 
     The amorphous solid may be made from a gel, and this gel may additionally comprise a solvent, included at 0.1-50 wt %. However, the inventors have established that the inclusion of a solvent in which the flavor is soluble may reduce the gel stability and the flavor may crystallize out of the gel. As such, in some cases, the gel does not include a solvent in which the flavor is soluble. 
     In some embodiments, the amorphous solid comprises less than 60 wt % of a filler, such as from 1 wt % to 60 wt %, or 5 wt % to 50 wt %, or 5 wt % to 30 wt %, or 10 wt % to 20 wt %. 
     In other embodiments, the amorphous solid comprises less than 20 wt %, suitably less than 10 wt % or less than 5 wt % of a filler. In some cases, the amorphous solid comprises less than 1 wt % of a filler, and in some cases, comprises no filler. 
     The filler, if present, may comprise one or more inorganic filler materials, such as calcium carbonate, perlite, vermiculite, diatomaceous earth, colloidal silica, magnesium oxide, magnesium sulphate, magnesium carbonate, and suitable inorganic sorbents, such as molecular sieves. The filler may comprise one or more organic filler materials such as wood pulp, cellulose and cellulose derivatives. In particular cases, the amorphous solid comprises no calcium carbonate such as chalk. 
     In particular embodiments which include filler, the filler is fibrous. For example, the filler may be a fibrous organic filler material such as wood pulp, hemp fiber, cellulose or cellulose derivatives. Without wishing to be bound by theory, it is believed that including fibrous filler in an amorphous solid may increase the tensile strength of the material. This may be particularly advantageous in examples wherein the amorphous solid is provided as a sheet, such as when an amorphous solid sheet circumscribes a rod of aerosolizable material. 
     In some embodiments, the amorphous solid does not comprise tobacco fibers. In particular embodiments, the amorphous solid does not comprise fibrous material. 
     In some embodiments, the aerosol generating material does not comprise tobacco fibers. In particular embodiments, the aerosol generating material does not comprise fibrous material. 
     In some embodiments, the aerosol generating substrate does not comprise tobacco fibers. In particular embodiments, the aerosol generating substrate does not comprise fibrous material. 
     In some embodiments, the aerosol generating article does not comprise tobacco fibers. In particular embodiments, the aerosol generating article does not comprise fibrous material. 
     In some cases, the amorphous solid may consist essentially of, or consist of a gelling agent, an aerosol generating agent, one or more active substances (such as a tobacco material and/or a nicotine source), water, and optionally a flavorflavour. 
     The amorphous solid may have any suitable area density, such as from 30 g/m 2  to 120 g/m 2 . In some embodiments, aerosol generating material may have an area density of from about 30 to 70 g/m 2 , or about 40 to 60 g/m 2 . In some embodiments, the amorphous solid may have an area density of from about 80 to 120 g/m 2 , or from about 70 to 110 g/m 2 , or particularly from about 90 to 110 g/m 2 . 
     In some examples, the amorphous solid in sheet form may have a tensile strength of from around 200 N/m to around 900 N/m. In some examples, such as where the amorphous solid does not comprise a filler, the amorphous solid may have a tensile strength of from 200 N/m to 400 N/m, or 200 N/m to 300 N/m, or about 250 N/m. Such embodiments are particularly useful where the amorphous solid is shredded and forms the second aerosol-forming composition. In some examples, such as where the amorphous solid comprises a filler, the amorphous solid may have a tensile strength of from 600 N/m to 900 N/m, or from 700 N/m to 900 N/m, or around 800 N/m. Such tensile strengths may be particularly suitable where the amorphous solid is disposed as part of the tubular substrate (in the first and/or second aerosol-forming composition). 
     Method of Manufacture of Tubular Substrate 
     The substrate may be manufactured by a method comprising (a) forming a slurry comprising components of the first aerosol-forming composition or precursors thereof, (b) applying the slurry to a sheet carrier, (c) setting the slurry to form a gel, (d) drying to form an amorphous solid, and (e) rolling to form a tube. 
     The step (b) of forming a layer of the slurry may comprise spraying, casting or extruding the slurry, for example. In some cases, the layer is formed by electrospraying the slurry. In some cases, the layer is formed by casting the slurry. 
     In some cases, the steps (b) and/or (c) and/or (d) may, at least partially, occur simultaneously (for example, during electrospraying). In some cases, these steps may occur sequentially. 
     In some examples, the slurry has a viscosity of from about 10 to about 20 Pa·s at 46.5° C., such as from about 14 to about 16 Pa·s at 46.5° C. 
     The step (c) of setting the gel may comprise the addition of a setting agent to the slurry. For example, the slurry may comprise sodium, potassium or ammonium alginate as a gel-precursor, and a setting agent comprising a calcium source (such as calcium chloride), may be added to the slurry to form a calcium alginate gel. 
     The total amount of the setting agent, such as a calcium source, may be 0.5-5 wt % (calculated on a dry weight basis). The inventors have found that the addition of too little setting agent may result in a gel which does not stabilize the gel components and results in these components dropping out of the gel. The inventors have found that the addition of too much setting agent results in a gel that is very tacky and consequently has poor handleability. 
     Alginate salts are derivatives of alginic acid and are typically high molecular weight polymers (10-600 kDa). Alginic acid is a copolymer of β-D-mannuronic (M) and a-L-guluronic acid (G) units (blocks) linked together with (1,4)-glycosidic bonds to form a polysaccharide. On addition of calcium cations, the alginate crosslinks to form a gel. The inventors have determined that alginate salts with a high G monomer content more readily form a gel on addition of the calcium source. In some cases therefore, the gel-precursor pay comprise an alginate salt in which at least about 40%, 45%, 50%, 55%, 60% or 70% of the monomer units in the alginate copolymer are a-L-guluronic acid (G) units. 
     In one particular case, the first and second aerosol-forming compositions both comprise amorphous solids. One comprises a flavorant and the other comprises a tobacco material. Optionally, one comprises a flavorant and no tobacco material or nicotine, and the second comprises a tobacco material and no flavorant. 
     The slurry itself may also form part of the invention. In some cases, the slurry solvent may consist essentially of or consist of water. In some cases, the slurry may comprise from about 50 wt %, 60 wt %, 70 wt %, 80 wt % or 90 wt % of solvent (WWB). 
     In cases where the solvent consists of water, the dry weight content of the slurry may match the dry weight content of the amorphous solid. Thus, the discussion herein relating to the solid composition is explicitly disclosed in combination with the slurry aspect of the invention. 
     Exemplary Embodiments 
     In some embodiments, the amorphous solid comprises menthol. 
     Particular embodiments comprising a menthol-containing amorphous solid may be particularly suitable for including in an aerosol generating article/assembly as a shredded sheet. In these embodiments, the amorphous solid may have the following composition (DWB): gelling agent (preferably comprising alginate, more preferably comprising a combination of alginate and pectin) in an amount of from about 20 wt % to about 40 wt %, or about 25 wt % to 35 wt %; menthol in an amount of from about 35 wt % to about 60 wt %, or from about 40 wt % to 55 wt %; aerosol generating agent (preferably comprising glycerol) in an amount of from about 10 wt % to about 30 wt %, or from about 15 wt % to about 25 wt % (DWB). 
     In one embodiment, the amorphous solid comprises about 32-33 wt % of an alginate/pectin gelling agent blend; about 47-48 wt % menthol flavorant; and about 19-20 wt % glycerol aerosol generating agent (DWB). 
     The amorphous solid of these embodiments may have any suitable water content. For example, the amorphous solid may have a water content of from about 2 wt % to about 10 wt %, or from about 5 wt % to about 8 wt %, or about 6 wt %. 
     As noted above, the amorphous solid of these embodiments may be included in an aerosol generating article/assembly as a shredded sheet (i.e. within the second aerosol-forming composition). The shredded sheet may be provided in the article/assembly blended with cut tobacco. Alternatively, the amorphous solid may be provided as a non-shredded sheet (in the first or second aerosol-forming composition). Suitably, the shredded or non-shredded sheet has a thickness of from about 0.015 mm to about 1 mm, preferably from about 0.02 mm to about 0.07 mm. 
     Particular embodiments of the menthol-containing amorphous solid may be particularly suitable for including in an aerosol generating article/assembly as a sheet (i.e. in the first or second aerosol-forming composition as part of the tubular substrate), such as a sheet circumscribing a rod of aerosolizable material (e.g. a second aerosol forming composition such as tobacco). In these embodiments, the amorphous solid may have the following composition (DWB): gelling agent (preferably comprising alginate, more preferably comprising a combination of alginate and pectin) in an amount of from about 5 wt % to about 40 wt %, or about 10 wt % to 30 wt %; menthol in an amount of from about 10 wt % to about 50 wt %, or from about 15 wt % to 40 wt %; aerosol generating agent (preferably comprising glycerol) in an amount of from about 5 wt % to about 40 wt %, or from about 10 wt % to about 35 wt %; and optionally filler in an amount of up to 60 wt % —for example, in an amount of from 5 wt % to 20 wt %, or from about 40 wt % to 60 wt % (DWB). 
     In one of these embodiments, the amorphous solid comprises about 11 wt % of an alginate/pectin gelling agent blend, about 56 wt % woodpulp filler, about 18% menthol flavorant and about 15 wt % glycerol (DWB). 
     In another of these embodiments, the amorphous solid comprises about 22 wt % of an alginate/pectin gelling agent blend, about 12 wt % woodpulp filler, about 36% menthol flavorant and about 30 wt % glycerol (DWB). 
     As noted above, the amorphous solid of these embodiments may be included as a sheet (which may be part of the tubular substrate). In one embodiment, the sheet is provided on a carrier comprising paper. In one embodiment, the sheet is provided on a carrier comprising metal foil, suitably aluminum metal foil. In this embodiment, the amorphous solid may abut the metal foil. 
     In one embodiment, the sheet forms part of a laminate material with a layer (preferably comprising paper) attached to a top and bottom surface of the sheet. Suitably, the sheet of amorphous solid has a thickness of from about 0.015 mm to about 1 mm. 
     In some embodiments, the amorphous solid comprises a flavorant which does not comprise menthol. In these embodiments, the amorphous solid may have the following composition (DWB): gelling agent (preferably comprising alginate) in an amount of from about 5 to about 40 wt %, or from about 10 wt % to about 35 wt %, or from about 20 wt % to about 35 wt %; flavorant in an amount of from about 0.1 wt % to about 40 wt %, of from about 1 wt % to about 30 wt %, or from about 1 wt % to about 20 wt %, or from about 5 wt % to about 20 wt %; aerosol generating agent (preferably comprising glycerol) in an amount of from 15 wt % to 75 wt %, or from about 30 wt % to about 70 wt %, or from about 50 wt % to about 65 wt %; and optionally filler (suitably woodpulp) in an amount of less than about 60 wt %, or about 20 wt %, or about 10 wt %, or about 5 wt % (preferably the amorphous solid does not comprise filler) (DWB). 
     In one of these embodiments, the amorphous solid comprises about 27 wt % alginate gelling agent, about 14 wt % flavorant and about 57 wt % glycerol aerosol generating agent (DWB). 
     In another of these embodiments, the amorphous solid comprises about 29 wt % alginate gelling agent, about 9 wt % flavorant and about 60 wt % glycerol (DWB). 
     The amorphous solid of these embodiments may be included in an aerosol generating article/assembly as a shredded sheet (i.e. as part of the second aerosol-forming composition), optionally blended with cut tobacco. Alternatively, the amorphous solid of these embodiments may be included in an aerosol generating article/assembly as a sheet (in the first and/or second aerosol-forming composition), such as a sheet (as part of the tubular substrate) circumscribing a rod of aerosolizable material (e.g. a second aerosol-forming composition such as tobacco). 
     In some embodiments, the amorphous solid comprises tobacco extract. In these embodiments, the amorphous solid may have the following composition (DWB): gelling agent (preferably comprising alginate) in an amount of from about 5 wt % to about 40 wt %, or about 10 wt % to 30 wt %, or about 15 wt % to about 25 wt %; tobacco extract in an amount of from about 30 wt % to about 60 wt %, or from about 40 wt % to 55 wt %, or from about 45 wt % to about 50 wt %; aerosol generating agent (preferably comprising glycerol) in an amount of from about 10 wt % to about 50 wt %, or from about 20 wt % to about 40 wt %, or from about 25 wt % to about 35 wt % (DWB). 
     In one embodiment, the amorphous solid comprises about 20 wt % alginate gelling agent, about 48 wt % Virginia tobacco extract and about 32 wt % glycerol (DWB). 
     The amorphous solid of these embodiments may have any suitable water content. For example, the amorphous solid may have a water content of from about 5 wt % to about 15 wt %, or from about 7 wt % to about 13 wt %, or about 10 wt %. 
     The amorphous solid of these embodiments may be included in an aerosol generating article/assembly as a shredded sheet (i.e. a second aerosol-forming composition), optionally blended with cut tobacco. Alternatively, the amorphous solid of these embodiments may be included in an aerosol generating article/assembly as a sheet (i.e. a first or second aerosol forming composition), such as a sheet circumscribing (i.e. a tubular substrate) a rod of aerosolizable material (e.g. a second aerosol-forming composition such as tobacco). Suitably, in any of these embodiments, the amorphous solid has a thickness of from about 50 μm to about 200 μm, or about 50 μm to about 100 μm, or about 60 μm to about 90 μm, suitably about 77 μm. 
     The slurry for forming this amorphous solid may also form part of the invention. In some cases, the slurry may have an elastic modulus of from about 5 to 1200 Pa (also referred to as storage modulus); in some cases, the slurry may have a viscous modulus of about 5 to 600 Pa (also referred to as loss modulus). 
     In some examples, the slurry has a viscosity of from about 10 to about 20 Pa·s at 46.5° C., such as from about 14 to about 16 Pa·s at 46.5° C. 
     Definitions 
     The active substance as used herein may be a physiologically active material, which is a material intended to achieve or enhance a physiological response. The active substance may for example be selected from nutraceuticals, nootropics, and psychoactives. The active substance may be naturally occurring or synthetically obtained. The active substance may comprise for example nicotine, caffeine, taurine, theine, vitamins such as B6 or B12 or C, melatonin, cannabinoids, or constituents, derivatives, or combinations thereof. The active substance may comprise one or more constituents, derivatives or extracts of tobacco,  cannabis  or another botanical. 
     In some embodiments, the active substance comprises nicotine. 
     In some embodiments, the active substance comprises caffeine, melatonin or vitamin B12. 
     As noted herein, the active substance may comprise one or more constituents, derivatives or extracts of  cannabis , such as one or more cannabinoids or terpenes. 
     Cannabinoids are a class of natural or synthetic chemical compounds which act on cannabinoid receptors (i.e., CB1 and CB2) in cells that repress neurotransmitter release in the brain. Cannabinoids may be naturally occurring (phytocannabinoids) from plants such as  cannabis , from animals (endocannabinoids), or artificially manufactured (synthetic cannabinoids).  Cannabis  species express at least 85 different phytocannabinoids, and are divided into subclasses, including cannabigerols, cannabichromenes, cannabidiols, tetrahydrocannabinols, cannabinols and cannabinodiols, and other cannabinoids. Cannabinoids found in  cannabis  include, without limitation: cannabigerol (CBG), cannabichromene (CBC), cannabidiol (CBD), tetrahydrocannabinol (THC), cannabinol (CBN), cannabinodiol (CBDL), cannabicyclol (CBL), cannabivarin (CBV), tetrahydrocannabivarin (THCV), cannabidivarin (CBDV), cannabichromevarin (CBCV), cannabigerovarin (CBGV), cannabigerol monomethyl ether (CBGM), cannabinerolic acid, cannabidiolic acid (CBDA), Cannabinol propyl variant (CBNV), cannabitriol (CBO), tetrahydrocannabmolic acid (THCA), and tetrahydrocannabivarinic acid (THCV A). 
     As noted herein, the active substance may comprise or be derived from one or more botanicals or constituents, derivatives or extracts thereof. As used herein, the term “botanical” includes any material derived from plants including, but not limited to, extracts, leaves, bark, fibers, stems, roots, seeds, flowers, fruits, pollen, husk, shells or the like. Alternatively, the material may comprise an active compound naturally existing in a botanical, obtained synthetically. The material may be in the form of liquid, gas, solid, powder, dust, crushed particles, granules, pellets, shreds, strips, sheets, or the like. Example botanicals are tobacco,  eucalyptus , star anise, hemp, cocoa,  cannabis , fennel, lemongrass, peppermint, spearmint, rooibos, chamomile, flax, ginger,  Ginkgo biloba , hazel, hibiscus, laurel, licorice (liquorice), matcha, mate, orange skin,  papaya , rose, sage, tea such as green tea or black tea, thyme, clove, cinnamon, coffee, aniseed (anise), basil, bay leaves, cardamom, coriander, cumin, nutmeg, oregano, paprika, rosemary, saffron, lavender, lemon peel, mint, juniper, elderflower, vanilla, wintergreen, beefsteak plant,  curcuma , turmeric, sandalwood, cilantro, bergamot, orange blossom, myrtle, cassis, valerian, pimento, mace, damien, marjoram, olive, lemon balm, lemon basil, chive,  carvi, verbena , tarragon, geranium, mulberry,  ginseng , theanine, theacrine, maca, ashwagandha, damiana, guarana, chlorophyll, baobab or any combination thereof. The mint may be chosen from the following mint varieties:  Mentha arvensis, Mentha  c.v.,  Mentha niliaca, Mentha  piperita,  Mentha piperita citrata  c.v.,  Mentha piperita  c.v.,  Mentha  spicata crispa,  Mentha  cordifolia,  Mentha  longifolia,  Mentha  suaveolens variegata,  Mentha  pulegium,  Mentha spicata  c.v. and  Mentha  suaveolens. 
     In some embodiments, the botanical is selected from  eucalyptus , star anise, cocoa and hemp. 
     In some embodiments, the botanical is selected from rooibos and fennel. 
     As used herein, the terms “flavor” and “flavorant” refer to materials which, where local regulations permit, may be used to create a desired taste, aroma or other somatosensorial sensation in a product for adult consumers. They may include naturally occurring flavor materials, botanicals, extracts of botanicals, synthetically obtained materials, or combinations thereof (e.g., tobacco,  cannabis , licorice (liquorice),  hydrangea , eugenol, Japanese white bark  magnolia  leaf, chamomile, fenugreek, clove, maple, matcha, menthol, Japanese mint, aniseed (anise), cinnamon, turmeric, Indian spices, Asian spices, herb, wintergreen, cherry, berry, red berry, cranberry, peach, apple, orange, mango, clementine, lemon, lime, tropical fruit,  papaya , rhubarb, grape, durian, dragon fruit, cucumber, blueberry, mulberry, citrus fruits, Drambuie, bourbon, scotch, whiskey, gin, tequila, rum, spearmint, peppermint, lavender, aloe vera, cardamom, celery, cascarilla, nutmeg, sandalwood, bergamot, geranium, khat, naswar,  betel , shisha, pine, honey essence, rose oil, vanilla, lemon oil, orange oil, orange blossom, cherry blossom,  cassia , caraway, cognac, jasmine, ylang-ylang, sage, fennel, wasabi, piment, ginger, coriander, coffee, hemp, a mint oil from any species of the genus  Mentha, eucalyptus , star anise, cocoa, lemongrass, rooibos, flax,  Ginkgo biloba , hazel, hibiscus, laurel, mate, orange skin, rose, tea such as green tea or black tea, thyme, juniper, elderflower, basil, bay leaves, cumin, oregano, paprika, rosemary, saffron, lemon peel, mint, beefsteak plant,  curcuma , cilantro, myrtle, cassis, valerian, pimento, mace, damien, marjoram, olive, lemon balm, lemon basil, chive,  carvi, verbena , tarragon, limonene, thymol, camphene), flavor enhancers, bitterness receptor site blockers, sensorial receptor site activators or stimulators, sugars and/or sugar substitutes (e.g., sucralose, acesulfame potassium, aspartame, saccharine, cyclamates, lactose, sucrose, glucose, fructose, sorbitol, or mannitol), and other additives such as charcoal, chlorophyll, minerals, botanicals, or breath freshening agents. They may be imitation, synthetic or natural ingredients or blends thereof. They may be in any suitable form, for example, liquid such as an oil, solid such as a powder, or gas. 
     The flavor may suitably comprise one or more mint-flavors suitably a mint oil from any species of the genus  Mentha . The flavor may suitably comprise, consist essentially of or consist of menthol. 
     In some embodiments, the flavor comprises menthol, spearmint and/or peppermint. 
     In some embodiments, the flavor comprises flavor components of cucumber, blueberry, citrus fruits and/or redberry. 
     In some embodiments, the flavor comprises eugenol. 
     In some embodiments, the flavor comprises flavor components extracted from tobacco. 
     In some embodiments, the flavor comprises flavor components extracted from  cannabis.    
     In some embodiments, the flavor may comprise a sensate, which is intended to achieve a somatosensorial sensation which are usually chemically induced and perceived by the stimulation of the fifth cranial nerve (trigeminal nerve), in addition to or in place of aroma or taste nerves, and these may include agents providing heating, cooling, tingling, numbing effect. A suitable heat effect agent may be, but is not limited to, vanillyl ethyl ether and a suitable cooling agent may be, but not limited to eucalyptol, WS-3. 
     As used herein, the term “aerosol generating agent” refers to an agent that promotes the generation of an aerosol. An aerosol generating agent may promote the generation of an aerosol by promoting an initial vaporization and/or the condensation of a gas to an inhalable solid and/or liquid aerosol. 
     Suitable aerosol generating agents include, but are not limited to: a polyol such as erythritol, sorbitol, glycerol, and glycols like propylene glycol or triethylene glycol; a non-polyol such as monohydric alcohols, high boiling point hydrocarbons, acids such as lactic acid, glycerol derivatives, esters such as diacetin, triacetin, triethylene glycol diacetate, triethyl citrate or myristates including ethyl myristate and isopropyl myristate and aliphatic carboxylic acid esters such as methyl stearate, dimethyl dodecanedioate and dimethyl tetradecanedioate. The aerosol generating agent may suitably have a composition that does not dissolve menthol. The aerosol generating agent may suitably comprise, consist essentially of or consist of glycerol. 
     As used herein, the term “tobacco material” refers to any material comprising tobacco or derivatives therefore. The term “tobacco material” may include one or more of tobacco, tobacco derivatives, expanded tobacco, reconstituted tobacco or tobacco substitutes. The tobacco material may comprise one or more of ground tobacco, tobacco fiber, cut tobacco, extruded tobacco, tobacco stem, reconstituted tobacco and/or tobacco extract. 
     The tobacco used to produce tobacco material may be any suitable tobacco, such as single grades or blends, cut rag or whole leaf, including Virginia and/or Burley and/or Oriental. It may also be tobacco particle ‘fines’ or dust, expanded tobacco, stems, expanded stems, and other processed stem materials, such as cut rolled stems. The tobacco material may be a ground tobacco or a reconstituted tobacco material. The reconstituted tobacco material may comprise tobacco fibers, and may be formed by casting, a Fourdrinier-based paper making-type approach with back addition of tobacco extract, or by extrusion. 
     As used herein, the terms “volatiles” and “aerosolizable components” may refer to any components of the inhaled aerosol including, but not limited to aerosol generating agents, flavorants, tobacco flavors and aromas, and nicotine. The terms “amorphous solid-derived volatiles”, “amorphous solid-derived aerosolizable components”, “tobacco-volatiles” and the like indicate in which component of the aerosol generating article the volatiles/aerosolizable components are arranged or derived from. 
     As used herein, the term “rod” generally refers to an elongate body which may be any suitable shape for use in an aerosol generating assembly. In some cases, the rod is substantially cylindrical. 
     All percentages by weight described herein (denoted wt %) are calculated on a dry weight basis, unless explicitly stated otherwise. All weight ratios are also calculated on a dry weight basis. A weight quoted on a dry weight basis refers to the whole of the extract or slurry or material, other than the water, and may include components which by themselves are liquid at room temperature and pressure, such as glycerol. Conversely, a weight percentage quoted on a wet weight basis refers to all components, including water. 
     As used herein, “heat profile”, “heating profile” and the like refer to the temperature exposure over time. Thus, “different” heat profiles may vary in the heating time, the point of heating initiation or termination, the time or rate at which the temperature is altered and the like. “Different” heat profiles may also vary in the maximum and minimum temperatures employed, or the temperature at any point in time may differ, for example. 
     For the avoidance of doubt, where in this specification the term “comprises” is used in defining the invention or features of the invention, embodiments are also disclosed in which the invention or feature can be defined using the terms “consists essentially of” or “consists of” in place of “comprises”. Reference to a material “comprising” certain features means that those features are included in, contained in, or held within the material. 
     The above embodiments are to be understood as illustrative examples of the invention. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.