Abstract:
Disclosed is a method for maintaining container contents in a desired ambient temperature and a container assembly for achieving the same. The method incorporates use of a container assembly comprising an outer bowl member, an inner vessel member and a lid member, all of which are constructed with porous materials. Critically-select portions of the outer bowl member, the inner vessel member and the lid member are glazed with a vapor-impervious coating while the remaining portions of the container assembly are left unglazed. The glazed portions thus provide an avenue for vapor or liquid media, emanating from temperature-maintaining matter, to permeate through the interstitial pores of the material by entering and exiting through the unglazed portions of the container assemblage. Container contents, housed in the lidded inner vessel member, are thus more efficiently maintained in a desired ambient temperature.

Description:
PRIOR HISTORY 
   This is a Divisional patent application claiming priority to U.S. patent application Ser. No. 10/201,477, filed in the United States Patent and Trademark Office on Jul. 23, 2002 now U.S. Pat. No. 6,840,396. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a method of refrigerating, heating, and storing incorporating use of a container assembly for refrigerating, heating, and storing substances for subsequent usage. More specifically, the present invention is primarily intended as a method for storing a substance in a temperature controlled environment whereby the target substance is contained within a first container and the first container is nestedly received in a second container. The second container houses a temperature-maintaining substance for maintaining the internal temperature of the first container. 
   2. Description of the Prior Art 
   The process of lowering a temperature and maintaining it in a given space for the purpose of chilling foods or preserving certain substances is commonly known as refrigeration. By placing a given temperature-controlled substance into a lowered temperature environment and maintaining the same in a desired ambient temperature, the resultant refrigeration checks both bacterial growth and adverse chemical reactions that would otherwise occur in normal atmosphere. The use of natural or manufactured ice for refrigeration purposes was widespread the world over until the early 1900&#39;s when mechanical or electric refrigerators became available, but is still commonly used to maintain temperature-controlled substances in a chilled ambient temperature. Ice or frozen water owes its effectiveness as a cooling agent to the fact that it has a constant fusion temperature of 0 Celcius (32 Fahrenheit). Other temperature-maintaining substances such as solid carbon dioxide (dry ice) have also proven to be effective refrigerants. Dry ice, for example, has no liquid phase at normal atmospheric temperature and sublimes directly from a solid state to a vapor phase at a temperature of −78.5 Celcius (−109.3 Fahrenheit). It is during this period of sublimation that solid carbon dioxide is effective for maintaining temperature-controlled products in low ambient temperatures. 
   The vapor of a substance refers to the gaseous state of a given substance. If confined at any temperature, the vapor emitted from any substance exerts pressure known as vapor pressure, and as the temperature of the substance is raised, the vapor pressure increases as a result of increased evaporation. When the local vapor pressure above a liquid becomes equal to the total pressure because of heat, boiling will occur. For most solids at ordinary temperatures and pressures, the vapor pressure is small or negligible. A finite vapor pressure exists, however, as the presence of water vapor over ice demonstrates. 
   Modern developments in refrigeration, heating, and storage techniques have provided various devices for maintaining temperature-controlled substances in a chilled or heated state so as to prepare the temperature-controlled substance for subsequent use. In this last regard, edible matter or food is often the target temperature-controlled substance and it is with this backdrop that the present invention is presented. The present invention harnesses the properties inherent in given temperature-maintaining matter, particularly the vapor pressure, for chilling or heating temperature-controlled substances for subsequent usage. Preferably, the present invention is intended as a serving vessel for mealtime. 
   In this last regard, it is noted that meals comprise not only the act or the time of eating a portion of food to satisfy an appetite, but often further comprise a social engagement in which situation those dining take pleasure in the visual experience of the meal as well as the edible quality of the meal. As is well known in the culinary arts, the visual presentation of a meal is a paramount consideration to the overall dining experience. Thus, in its basic form and function, the present invention incorporates specific materials and structure to form an aesthetically pleasing appearance, which results in a novel container assembly for storing substances in a preferred ambient temperature. 
   Among food items requiring refrigeration, heating, and storage are butter, margarine, and other similar spreads. The preservation of butter and the like present unique problems, not applicable to other condiments, such as ketchup, salt, sugar and so forth. For example, when using butter or similar other spreads in cooking, the butter and spreads are often required to be melted or soften prior to their addition to the recipe. However, when served directly at the meal, butter or similar other spreads are usually required to be chilled and maintained in a solid state. In an effort to provide for these requirements, many devices have been developed in an effort to provide an apparatus for maintaining temperature-controlled substances in a refrigerated or heated ambient temperature, some of which are described hereinafter. 
   U.S. Pat. No. 2,507,425 (&#39;425 Patent), which issued to Swartout, discloses a Double Bowl and Cover. The Double Bowl and Cover discloses a two-bowl and cover assemblage, in which a first bowl is nestedly received in a second bowl. Support tab members on the second bowl hold receive and support similarly placed suspension tab members on the first bowl such that when nested, a relatively uniform space is provided between the outer surface of the inner bowl and the inner space of the second bowl. It is contemplated that a water jacket fills the relatively uniform space for maintaining the target temperature-controlled substance in a desired ambient temperature. It will thus be seen, however, that the &#39;425 Patent does not teach the use of porous material in the construction of the double bowl assemblage nor does the &#39;425 Patent teach the application of vapor-impervious glazed coating on critically-select portions of the porous material for allowing vapor from the water jacket to permeate through the porous material in a controlled manner for improving the temperature-maintaining characteristics of the Double Bowl and Cover. 
   U.S. Pat. No. 3,130,288 (&#39;288 Patent) and U.S. Pat. No. 3,241,706 (&#39;706 Patent), which issued to Monaco et al., disclose Food-Service Devices. The Food Service-Devices each disclose the use of a deep pan for retaining temperature-maintaining matter such as heated or chilled water bath and at least one smaller tray-shaped container for supporting food items above the water bath. The tray-shaped container may be nestedly placed into the deep pan, which smaller tray-shaped containers are enclosed by a translucent, preferably dome-shaped cover or lid, for the visual benefit of passersby. The temperature-maintaining substance thus contributes to the maintenance of a desired temperature in the enclosed tray-shaped containers. Neither the &#39;288 Patent nor the &#39;706 Patent teach the use of porous material in the construction of the deep pan, smaller tray-shaped containers, or translucent dome-shaped lid. Furthermore, neither the &#39;288 Patent nor the &#39;706 Patent teach the application of vapor-impervious glazed coating on critically-select portions of the deep pan, smaller tray-shaped container or cover for allowing vapor from the water bath to permeate through porous material in a controlled manner for improving the temperature-maintaining characteristics of the Food-Service Devices. 
   U.S. Pat. No. 3,670,916 (&#39;916 Patent), which issued to Alpert, discloses a Food Containerization assembly. This invention teaches an insulated food container having an outer vessel formed in part of heat-resistant materials, which outer vessel comprises an upper peripheral ledge. An inner vessel, adapted to hold food, has a peripheral flange, which flange rests on the peripheral ledge and thus disposes the inner vessel in gapped relation to the outer vessel member. The gapped relation structurally results in an insulative layer of air between the inner and outer vessel members. The container is closed by a lid having suitable means to sealably engage the rim portion of the outer vessel member and has a conically-shaped portion, the vertex of which is fracturable under high internal pressure to provide relief of the vapor pressure that may accumulate within the sealed container. It will thus be seen that the &#39;916 Patent does not teach the use of porous material in the construction of the outer vessel member, the inner vessel member, or the lid member. It will be further seen that the &#39;916 Patent does not teach the application of vapor-impervious glazed coating on critically-select portions of the outer vessel member, inner vessel member or lid for allowing vapor in the insulative layer of air between the inner and outer vessel members to permeate through porous material in a controlled manner for improving the temperature-maintaining characteristics of the Food Containerization assembly. 
   U.S. Pat. No. 4,005,586 (&#39;586 Patent), which issued to Lyons, discloses a Refrigerated Butter Dish, known in the marketplace as the BUTTER BELL CROCK™ brand butter dish. The Refrigerated Butter Dish comprises a receptacle for containing crushed ice and an invertable cover unit which has on one side thereof a handle for lifting the cover and on the other an outwardly extending tapered skirt defining interiorly thereof a butter receiving chamber. When the dispenser is not being used, the cover is positioned so that the skirt portion depends inwardly of the receptacle, keeping the butter contained therein in close proximity with the crushed ice. When it is desired to remove the butter from the dispenser, the cover is inverted so that the skirt portion extends upwardly, making the butter chamber readily accessible to the user. The &#39;586 Patent thus discloses that the skirt must be inverted 180 degrees for removing the butter and returned to an upside-down position for storing the butter against the ice. The &#39;586 Patent thus further shows that the Refrigerated Butter Dish is susceptible to mixing of the butter with any melted ice and is impractical for refrigerating melted or softened butter, which may fall out of the skirt when turned upside-down. In this last regard, it is further noted that butter may easily become contaminated by coming into contact with the ice water solution in the receptacle for containing crushed ice, which is a notable disadvantage of the Refrigerated Butter Dish. 
   Furthermore, the &#39;586 Patent does not teach the use of porous material in the construction of the receptacle for containing crushed ice or the invertable cover member. Further, the &#39;586 Patent does not teach the application of vapor-impervious glazed coating on critically-select portions of the receptacle for containing crushed ice or the invertable cover member for allowing vapor from the space between the crushed ice receptacle and the invertable cover member to permeate through the interstitial pores of the structure in a controlled manner for improving the temperature-maintaining characteristics of the Refrigerated Butter Dish. 
   Moreover, U.S. Pat. No. 5,372,274 (&#39;274 Patent), which issued to Freedland, discloses a Container for the Storage and Serving of Food Products comprising an outer bowl, and an inner bowl receivable within the outer bowl such that a space is defined between the outer and inner bowls for containing ice or hot packs for cooling or heating the walls of the inner bowl. The device of the &#39;274 Patent further comprises a drain assembly for selectively draining excess salad dressing or water out of the inner bowl. The drain assembly is formed in part from a bottom wall portion of the inner bowl and a drain cover plate that is slidably mounted over the wall portion. Both the bottom wall portion of the inner bowl and the drain cover plate include mutually registrable patterns of drain ports which may be slidably moved into alignment when drainage of the inner bowl is desired. However, the usage of a drain system in the bottom of the inner bowl can allow for melted or softened food products, like butter and spread, to spill or drain unnecessarily or unwantingly from the device of the &#39;274 Patent. Thus, it will be seen that the &#39;274 Patent does not teach the use of porous material in the construction of the outer or inner bowl members. Further, the &#39;274 Patent does not teach the application of vapor-impervious glazed coating on critically-select portions of the outer and inner bowl member for allowing chilled or heated vapors from the space between the outer and inner bowl members to permeate through porous material in a controlled manner for improving the temperature-maintaining characteristics of the Container for the Storage and Serving of Food Products. 
   It is noted that none of the prior art teaches a container assembly comprising nested elements and a lid member, wherein the nested elements and lid member are constructed from porous materials and which porous material is coated with a vapor-impervious glazed coating glazing. Further, none of the prior art teaches a container assembly which comprises vapor-impervious glazed coating on critically select portions of the nested elements for controlling the path of permeating vapor. In this regard, vapor from temperature-maintaining matter located in the space between nested elements, although present in the prior art systems, has not been shown to be harnessed for improving the maintenance of temperature in the chamber holding temperature-controlled substances. The prior art thus perceives a need for a container assembly comprising porous materials, which when coated with a vapor-impervious glazed coating glazing on critically select portions of the individual components, directs permeating vapor through the interstitial pores of the structure for improving the temperature-maintaining characteristics of the container assembly. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an object of the present invention to provide a container assembly that can refrigerate, heat, and store substances, such as butter and similar other spreads for use in cooking, serving, and the like. Another object of the present invention is to provide a container assembly, which harnesses vapor from temperature-maintaining matter located in an inferior chamber, to improve the temperature-maintaining characteristics of the container assembly. Moreover, the vapor-harnessing container assembly would provide a controlled self-sustaining environment minimizing unnecessary spillage while maximizing refrigeration or heating of the target temperature-controlled substance located in a superior chamber. It is a further object of the present invention to provide a container assembly that can also be portable and separable for conveniently storing temperature-controlled substances and for enabling users to easily gain access to the temperature-controlled substance contained therein. In this last regard, it is a further object of the present invention to provide a container assembly adapted for serving dish use, which is uniquely configured such that, in its structural design, the serving dish assembly further contributes to an aesthetically pleasing serving dish for improving the mealtime experience. Further, it is an object of the present invention to provide a serving dish, which will maintain temperature-controlled substances at a desired temperature in either a covered or uncovered state. 
   To achieve these and other readily apparent objectives, the present invention provides a container assembly and method for maintaining a temperature-controlled substance in an ambient temperature so as to store the temperature-controlled substance in a ready state for consumption and/or use. In particular, it is contemplated that butter, margarine or other similar spreads may be kept in a ready state for consumption by storing the same in the present invention. In this regard, the present invention generally comprises an outer bowl member, an inner vessel member, and a lid member, which are each preferably constructed with a hydrophilic, porous ceramic material. 
   The outer bowl member is designed for containing temperature-maintaining matter or preferably an iced or chilled water solution, or other liquid medium having similar volatility characteristics. The present invention preferably utilizes the resultant vapor from the volatile liquid medium to function properly. The outer bowl member comprises an inner bowl surface, an outer bowl surface, a superior bowl support rim, and an inferior bowl contact surface. The inner bowl surface, the outer bowl surface and the superior bowl support rim each further comprise a vapor-impervious glazed coating to prevent the passage of vapor through the vapor-impervious glazed coating so as to directionally utilize vapor emanating from the temperature-maintaining medium. 
   The inner vessel member is designed for containing a temperature-controlled substance, or in particular, a food substance such as butter or similar other spread. The inner vessel member comprises an inner vessel surface, an outer vessel surface, a superior perimeter flange, a superior vessel contact seat and an inferior vessel portal ridge. The superior perimeter flange is sized and shaped to snug down or rest atop the superior bowl support rim for preventing the passage of vapor between the juncture of the superior perimeter flange and the superior bowl support rim. The superior vessel contact seat is spatially-located inwardly adjacent to the superior perimeter flange and has a predetermined contact seat perimeter. The outer vessel surface is sized and shaped to rest in gapped relation to the inner bowl surface thus creating a container cavity for retaining the vapors from the temperature-maintaining matter. The inner vessel surface, the outer vessel surface and the superior perimeter flange are each further provided with a vapor-impervious glazed coating to prevent passage of vapor through the vapor-impervious glazed coating and facilitate directed movement of the vapor through the porous structure of the inner vessel member. 
   The lid member functions to optionally enclose the inner vessel member and comprises an inner lid surface, an outer lid surface, a superior lifting protrusion, and an inferior lid contact surface. The inferior lid contact surface has a predetermined lid contact surface perimeter, which is slightly less in dimension than the dimension of the superior contact seat perimeter. The inferior lid contact surface is sized and shaped to snug down or rest atop the superior vessel contact seat for preventing the passage of vapor between the juncture of the inferior contact surface and the superior contact seat. 
   The inner lid surface, the outer lid surface, and the superior lifting protrusion each further comprise a vapor-impervious glazed coating to prevent the passage of vapor through the vapor-impervious glazed coating. Unglazed portions of the container assembly, namely, the superior vessel contact seat, the inferior vessel portal ridge and the inferior lid contact surface thus allow vapor to permeate throughout the porous ceramic material to facilitate the maintenance of temperature within the enclosed inner vessel member for temperature-controlling the target substance. 
   The porous ceramic material comprising the inner vessel member thus further allows vapor to permeate through the superior vessel contact seat and into the inferior lid contact surface. The passage of vapor in this manner thus further facilitates the maintenance of temperature in the enclosed inner vessel member. Additionally, the perimeter of the inferior lid contact surface, having a measured dimension less than the measured dimension of the contact seat perimeter, thus exposes a contact seat vent portion of the superior vessel contact seat. The contact seat vent portion allows vapor to permeate from the superior vessel contact seat to the air adjacent the enclosed inner vessel member for further facilitating the maintenance of temperature in the enclosed inner vessel member. 
   Additionally, other structural features of the present invention are further disclosed. For example, the inner lid surface and the outer lid surface of the lid member may further define an ellipsoidal upper shell, which increases the internal volume of the enclosed inner vessel member. Users of the present invention may thus place a more voluminous temperature-controlled substance therein. Additionally, the superior perimeter flange further comprises at least one outwardly extending handle for facilitating the removal of the inner vessel member from the outer bowl member. In an alternative embodiment, the porous ceramic material used to construct the container assembly components may be further defined by comprising oven-proofed material for use in heated environments. Additionally, in an alternative embodiment, the container assembly components, or the outer bowl member, the inner vessel member and the lid member are each shaped so as to have a substantially circular horizontal cross section. Further, the inferior bowl contact surface may include an inferior bowl perimeter ridge, which ridge elevates the inferior bowl contact surface from a contact surface so as to prevent temperature-related damage to the contact surface. 
   The present invention further provides a method of maintaining a temperature-controlled substance in a desired ambient temperature, which method comprises a series of steps. In the first instance, an outer bowl member, as summarized above, is provided. Temperature-maintaining matter having certain volatility is then placed into the outer bowl member, from which vapor is allowed to permeate. An inner vessel member, as summarized above, is then provided. Into the inner vessel member is placed a temperature-controlled substance, such as butter or similar other spread. The inner vessel member with its contents is then nested into the outer bowl member so as to create a container cavity for retaining the vapor. A lid member, as summarized above, is then further provided, which lid member encloses the inner vessel member for maintaining the temperature-controlled substance in the desired ambient temperature. Vapor from the temperature-maintaining substance is thus allowed to permeate from the container cavity through the inferior vessel portal ridge between the inner vessel and outer vessel surfaces, through the superior vessel contact seat and into the inferior lid contact surface. The passage of vapor in this manner thus further facilitates the maintenance of temperature in the enclosed inner vessel member. Additionally as noted above, the perimeter of the inferior lid contact surface, having a measured dimension less than the measured dimension of the contact seat perimeter, thus exposes a contact seat vent portion of the superior vessel contact seat. The contact seat vent portion allows vapor to permeate from the superior vessel contact seat to the air adjacent the enclosed inner vessel member for further facilitating the maintenance of temperature in the enclosed inner vessel member. 
   Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or apparent from, the following description and the accompanying drawing figures. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features of my invention will become more evident from a consideration of the following detailed description of my patent drawings, as follows: 
       FIG. 1  is a perspective view of the preferred embodiment of the container assembly in an assembled state. 
       FIG. 2  is a cross-sectional side view of the embodiment of  FIG. 1  showing suspended placement of the enclosed inner vessel member within the outer bowl member including a container cavity holding temperature-maintaining matter. 
       FIG. 3  is a fragmentary top plan view of the preferred embodiment of the container assembly showing the structural interaction of the primary components of the container assembly with the components partially illustrated in phantom. 
       FIG. 4  is a top plan view of the lid member showing the inferior lid contact surface in phantom. 
       FIG. 5  is a cross-sectional side view of the lid member of  FIG. 4 . 
       FIG. 5(   a ) is a fragmentary bottom plan view of the lid member of  FIG. 5  showing the inferior lid contact surface. 
       FIG. 6  is a top plan view of the inner vessel member nested inside the outer bowl member showing the superior vessel contact seat. 
       FIG. 7  is a cross-sectional side view of the inner vessel member of  FIG. 6  showing placement therein of a substance, such as food. 
       FIG. 8  is a top plan view of the outer bowl member showing superior bowl support rim. 
       FIG. 9  is a cross-sectional side view of the outer bowl member of  FIG. 8 . 
       FIG. 10  is a bottom plan view of the inner vessel member of  FIG. 7  showing the inferior vessel portal ridge. 
       FIG. 11  is a perspective view of an alternative embodiment of the container assembly in an assembled state. 
       FIG. 12  is a top plan view of an alternative lid member showing the inferior lid contact surface in phantom. 
       FIG. 13  is a cross-sectional side view of the lid member of  FIG. 12 . 
       FIG. 13(   a ) is a fragmentary bottom plan view of the lid member of  FIG. 13  showing the inferior lid contact surface. 
       FIG. 14  is a top plan view of an alternative inner vessel member showing the superior vessel contact seat. 
       FIG. 15  is a cross-sectional side view of the inner vessel member of  FIG. 14 . 
       FIG. 15(   a ) is a fragmentary bottom plan view of the inner vessel member of  FIG. 15  showing the inferior vessel portal ridge. 
       FIG. 16  is a top plan view of an alternative outer bowl member showing the superior bowl support rim. 
       FIG. 17  is a cross-sectional side view of the outer bowl member of  FIG. 16 . 
       FIG. 18  is a cross-sectional side view of an alternative embodiment of the container assembly in an assembled state. 
       FIG. 19  is a side plan view of an alternative outer bowl member with parts broken away showing the inner bowl surface and outer bowl surface in an unglazed state. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to the drawings, the preferred embodiment of the present invention concerns a container assembly  10  as perspectively illustrated in  FIG. 1  for maintaining a temperature-controlled substance in a preferred ambient temperature so as to store the temperature-controlled substance in a ready state for consumption and/or use. In particular, it is contemplated that butter, margarine or other similar spreads may be kept in a ready state for consumption by storing the same in the present invention as opposed to being forced to store the spread material in a conventional refrigerating appliance, where such appliance storage may be inconvenient for serving purposes. The present invention thus provides a freely transportable container assembly  10 , which maintains a preferred temperature in a removably-lidded chamber, designed primarily for serving purposes. 
   In this last regard, it is noted that meals comprise not only the act or the time of eating a portion of food to satisfy an appetite, but often further comprise a social engagement where those dining take pleasure in the visual experience of the meal as well as the edible quality of the meal. As is well known in the culinary arts, the visual presentation of a meal is of paramount importance to the overall dining experience. Thus, in its basic form and function, the present invention incorporates specific materials and structure to form an aesthetically pleasing container assembly, which results in a novel container assembly for storing substances in a preferred ambient temperature. 
   While it is contemplated that container assembly  10  may either storably refrigerate or storably heat a target food substance, it is not intended that the present invention be limited solely to a container assembly for use with food items. Rather it is intended that the scope of the present invention may include a container assemblage for refrigerating, heating, and storing substances not ordinarily associated with meals or the dining experience, such as medical products, plant products, pet products, and the like. 
   As is illustrated in  FIGS. 1-9 , inclusive, the preferred embodiment of the present invention comprises container assembly  10 , which is also commercially known in the kitchenware marketplace as a BUTTER BOAT™ brand spread serving dish. Container assembly  10  generally comprises an outer bowl member  20 , an inner vessel member  40 , and a lid member  60 , which are each fashioned from breathable or porous materials. In this last regard, excellent results have been shown when hydrophilic, open-pore-structured porous ceramic materials are used in the construction of container assembly  10 . Open pore structure is here defined as comprising material that permits a fluid or vapor to move from one surface to an opposing surface in the material through a convoluted pathway of interconnecting networked channels. Further description of the preferred materials and movement of fluid or vapor through the interstitial pores is found below under the section entitled: DISCUSSION OF PREFERRED MATERIALS. 
   Outer bowl member  20 , as is illustrated in  FIGS. 1 ,  2 ,  8  and  9 , is an open-top bowl-shaped container and is preferably fashioned to have an elliptic horizontal cross-section or approximate an elliptic shape when viewed from a top plan view as specifically illustrated in  FIG. 8 . Outer bowl member  20  functions to retain or contain temperature-maintaining matter. It is intended that the temperature-maintaining matter may be further defined by most often comprising a volatile liquid solution. In this last regard, excellent results have been shown when chilled water-based solutions have been used to maintain a cooler ambient temperature and when heated water-based solutions have been used to maintain a warmer ambient temperature.  FIG. 2  illustrates a typical ice-water solution  100  commonly used to refrigerate temperature-controlled substances. As is well known in the thermodynamic arts, water is an excellent retainer of its thermal energy. In other words, water-based solutions tend to lose heat energy relatively slowly, heat energy being defined as the energy, which is transferred from a higher-temperature composition to a lower-temperature composition because of a temperature difference. It is further contemplated, however, that other liquid media having similar volatility characteristics and heat energy retention characteristics compared to water-based solutions may also be utilized. The present invention attempts to harness the inherent off-vaporing or permeation of vapor that occurs when volatile temperature-maintaining matter is utilized. The present invention thus depends upon the resultant off-vapor or permeating vapor to function properly. As in known in the prior art, water as vapor effectively distributes uniformly throughout a porous material and in this regard, it is the preferred temperature-maintaining matter substance of choice. 
   Outer bowl member  20  comprises an inner bowl surface  22  as illustrated in  FIGS. 8 and 9 ; an outer bowl surface  24  as illustrated in  FIGS. 1 ,  2  and  9 ; a superior bowl support rim  26  as illustrated in  FIGS. 2 ,  3 ,  8  and  9 ; and an inferior bowl contact surface  28  as illustrated in  FIGS. 2 and 9 . Inner bowl surface  22 , outer bowl surface  24  and superior bowl support rim  26  each further preferably comprise a hydrophobic, vapor-impervious, glazed coating, preferably of a type that functions to prevent passage or permeation of vapor or water-based solution through the vapor-impervious glazed coating, thus forcing permeating vapor in an upward direction toward the open-top of the bowl-shaped outer bowl member  20 . Preferably, inferior bowl contact surface  28  is left unglazed. Left unglazed, inferior bowl contact surface  28  thus increases frictional forces between inferior bowl contact surface  28  and a contact surface upon which container assembly  10  is placed, thus reducing the tendency for outer bowl member  20  to slide along the contact surface. A line of demarcation may also be added to inner bowl surface  22  for aiding users in the placement of temperature-maintaining matter into outer bowl member  20  without overfilling the same. 
   Inner vessel member  40 , as is illustrated in  FIGS. 1 ,  2 ,  3 ,  6 ,  7  and  10 , is also an open-top bowl-shaped container being sized and shaped for nested placement in outer bowl member  20  and is therefore, preferably fashioned to also have an elliptic horizontal cross-section or approximate an elliptic shape when viewed from a top plan view or bottom plan view as specifically illustrated in  FIGS. 6 and 10 . Inner vessel member  40  primarily functions to retain or contain a temperature-controlled substance  101  as shown in  FIG. 7 . Temperature-controlled substance  101 , as indicated above, may include foodstuffs, medicinal or medical products, plant products, pet products, and other similar temperature-dependent items. As further noted, inner vessel member is also preferably constructed with porous or breathable ceramic materials and generally comprises an inner vessel surface  42  as illustrated in  FIGS. 2 ,  3 ,  6  and  7 ; an outer vessel surface  44  as illustrated in  FIGS. 2 ,  7  and  10 ; a superior perimeter flange  46  as illustrated in  FIGS. 1 ,  3 ,  6  and  10 ; a superior vessel contact seat  48  as illustrated in  FIGS. 1 ,  3 ,  6  and  7 ; and an inferior vessel portal surface or ridge  50  as illustrated in  FIGS. 2 ,  7  and  10 . Superior perimeter flange  46  is sized and shaped to snug down or snugly rest atop superior bowl support rim  26 . The junction between superior perimeter flange  46  and superior bowl support rim  26  is snug or gapless for preventing the passage or permeation of vapor through gaps between the junction point of superior perimeter flange  46  and superior bowl support rim  26 . Superior vessel contact seat  48  is spatially-located inwardly adjacent to superior perimeter flange  46  and has a critical contact seat perimeter dimension, which dimension includes an inner seat perimeter  49 ( a ) and an outer seat perimeter  49 ( b ). Inner seat perimeter  49 ( a ) and outer seat perimeter  49 ( b ) thus have a certain seat width measured therebetween, as is illustrated in  FIG. 6 . 
   As inner vessel member  40  and outer bowl member  20  nest together in the described fashion, outer vessel surface  44  is sized and shaped to rest in gapped relation to inner bowl surface  22  as shown in  FIG. 2 , thus creating a container cavity for retaining vapor and the temperature-maintaining matter. Inner vessel surface  42 , outer vessel surface  44  and superior perimeter flange  46  are further defined by preferably comprising a hydrophobic, vapor-impervious, glazed coating, preferably of a type that functions to prevent passage or permeation of vapor or water-based solution through the vapor-impervious glazed coating, thus forcing vapor, permeating from the volatile temperature-maintaining matter, through unglazed inferior vessel portal ridge  50 , which then may further permeate the structural space sandwiched between inner vessel surface  42  and outer vessel surface  44 . Further, the vapor may then exit the structural space between inner vessel surface  42  and outer vessel surface  44  via superior vessel contact seat  48 . Inner vessel surface  42 , outer vessel surface  44  and superior perimeter flange  46 , when provided with a vapor-impervious glazed coating, thus form a porous conduit through which vapor may permeate. Further discussion is outlined below under the section entitled: DISCUSSION OF PREFERRED MATERIALS regarding capillary action of water through the porous media should the user overfill outer bowl member  20  above the proposed line of demarcation on inner bowl surface  22 . 
   As indicated, a significant aspect of the present invention is that inner vessel member  40  is sized and shaped for placement within the interior of outer bowl member  20  in a removable stacking relationship, as is illustrated in  FIGS. 1 ,  2 ,  3  and  6 . In other words, inner vessel member  40  may be stacked inside of outer bowl member  20  and then removed, when needed, for independent usage. In this last regard, superior perimeter flange  46  may further comprise at least one outwardly extending handle  47  for facilitating the removal of inner vessel member  40  from outer bowl member  20  as shown in  FIGS. 1 ,  2 ,  3 ,  6 ,  7  and  10 . Preferably, superior perimeter flange  46  has two outwardly extending handles  47  opposite one another for symmetry and for safety reasons. Symmetrical handle structure contributes to a more aesthetically pleasing appearance and in most cases two handles are safer insofar as a user&#39;s left and right hand may more easily lift two handles opposite one another. Outwardly extending handles  47  thus provide for easy grasp and removal of inner vessel member  40  from outer bowl member  20 . 
   Lid member  60  is provided being sized and shaped for seatedly enclosing inner vessel member  40  and is further fashioned to have an elliptic horizontal cross-section or approximate an elliptical shape when viewed from a top plan view as specifically illustrated in  FIG. 4 . Lid member  60  has an inner lid surface  62  as illustrated in  FIGS. 5 and 5(   a ); an outer lid surface  64  as illustrated in  FIGS. 1 ,  2 ,  4  and  5 ; a superior lifting protrusion  66  as illustrated in  FIGS. 1 ,  2 ,  4  and  5 ; and an inferior lid contact surface  68  as illustrated in  FIGS. 5 and 5(   a ). Inferior lid contact surface  68  has a lid contact surface perimeter of a critical contact surface perimeter dimension, which dimension includes an inner lid perimeter  69 ( a ) and an outer lid perimeter  69 ( b ). Inner lid perimeter  69 ( a ) and outer lid perimeter  69 ( b ) thus have a certain lid contact surface width measured therebetween, as is illustrated in  FIG. 5(   a ). 
   Inferior lid contact surface  68  is sized and shaped to snug down or snugly rest atop superior vessel contact seat  48 . The junction between superior vessel contact seat  48  and inferior lid contact surface  68  is snug or gapless for preventing the passage or permeation of vapor through gaps between the junction point of superior vessel contact seat  48  and inferior lid contact surface  68 . Further, the measured width between inner lid perimeter  69 ( a ) and outer lid perimeter  69 ( b ) is less than the measured width between inner seat perimeter  49 ( a ) and outer seat perimeter  49 ( b ). More precisely, inner lid perimeter  69 ( a ) is substantially the same shape and dimension of inner seat perimeter  49 ( a ), but outer lid perimeter  69 ( b ) has a lesser dimension (though same shape) as outer seat perimeter  49 ( b ). Thus the outer edge of inferior lid contact surface  68  terminates at a point intermediate the measured width between inner seat perimeter  49 ( a ) and outer seat perimeter  49 ( b ), thus exposing a portion of superior contact seat  68  of enclosed inner vessel member  40  to the air or creating a contact seat vent  52  as illustrated in  FIG. 1 . 
   Inner lid surface  62 , outer lid surface  64  and superior lifting protrusion  66  are each further defined by preferably comprising a hydrophilic, vapor-impervious, glazed coating, preferably of a type that functions to prevent passage or permeation of vapor or water-based solution through the vapor-impervious glazed coating, thus forcing vapor, permeating from the volatile temperature-maintaining matter in the container cavity, through unglazed inferior vessel portal ridge  50 , through superior contact seat  48 , and either into inferior lid contact surface  68  or into the air adjacent container assembly  10  via contact seat vent  52 . 
   Inner lid surface  62  and outer lid surface  64  preferably define an ellipsoidal upper shell for increasing the internal volume of the enclosed inner vessel member as shown in  FIGS. 2 and 5 . By thus increasing the internal volume of the enclosed inner vessel member  40 , users are enabled to place more voluminous temperature-controlled substances  101  such as food or other substances therein. 
   As is commonly known, the flow or transfer of heat energy will cease when the temperatures of two adjacent compositions become equal. This is true even if the two compositions are composed of different substances. Heat energy thus flows spontaneously from heated compositions or objects to cooler compositions or objects, but never vice versa. The permeation of vapor through the unglazed portions of container assembly  10  as described thus facilitates the maintenance of temperature in the enclosed inner vessel member  40 . By providing components, the interstices of which become saturated with a temperature-maintaining vapor, heat energy transfer from warmer regions to cooler regions is more uniform using the present invention. 
   First Alternative Embodiment 
   A first alternative embodiment of the present invention concerns a container assembly  80  as perspectively illustrated in  FIG. 11 . Container assembly  80  is virtually identical to container assembly  10  save for having differently shaped primary components, namely, an outer bowl member  82 , an inner vessel member  84  and lid member  86  all of which have a substantially circular, horizontal cross-section or circular shape when viewed from a top plan view. Outer bowl member  82  is thus illustrated in  FIG. 16 ; inner vessel member  84  is thus illustrated in  FIG. 14 ; and lid member  86  is thus illustrated in  FIG. 12 . Container assembly  80  is designed for placement of more voluminous quantities of temperature-controlled substance into the enclosed inner vessel member  84 . In this last regard, it is contemplated that container assembly  80  is designed primarily for the placement of food or other substances, which are to be maintained in a heated ambient temperature. In this regard, container assembly  80  is further described by preferably comprising oven-proofed porous material so as to enable users to place the same in ovens or similar other chambers used for heating. 
   Outer bowl member  82 , as is illustrated in  FIGS. 11 ,  16 ,  17  and  18 , is an open-top bowl-shaped container and is preferably fashioned to have a substantially circular horizontal cross-section or approximate a circular shape when viewed from a top plan view as specifically illustrated in  FIG. 16 . Outer bowl member  82  functions to retain or contain temperature-maintaining matter, such as heated water-based solutions. 
   Outer bowl member  82  further comprises inner bowl surface  22  as illustrated in  FIGS. 16 and 17 ; outer bowl surface  24  as illustrated in  FIGS. 16 ,  17  and  18 ; superior bowl support rim  26  as illustrated in  FIGS. 16 and 17 ; and inferior bowl contact surface  28  as illustrated in  FIGS. 17 and 18 . Inner bowl surface  22 , outer bowl surface  24  and superior bowl support rim  26  each further preferably comprise a hydrophilic, vapor-impervious, glazed coating vapor-impervious glazed coating, preferably of a type that functions to prevent passage or permeation of vapor or water-based solution through the vapor-impervious glazed coating glazed coating, thus forcing permeating vapor in an upward direction toward the open-top of the bowl-shaped outer bowl member  82 . Preferably, inferior bowl contact surface  28  is left unglazed. Left unglazed, inferior bowl contact surface  28  thus increases frictional forces between inferior bowl contact surface  28  and a contact surface upon which container assembly is placed, thus reducing the tendency for outer bowl member  82  to slide along the contact surface. A line of demarcation may also be added to inner bowl surface  22  for aiding users in the placement of temperature-maintaining matter into outer bowl member  82  without overfilling the same. 
   Further, inferior bowl contact surface  28  may further comprise an inferior bowl perimeter ridge  30  as illustrated in  FIGS. 17 and 18 . Inferior bowl perimeter ridge  30  thus elevates inferior bowl contact surface  28  from a contact surface so as to prevent temperature-related damage to the contact surface. Inferior bowl contact ridge  30  is also preferably unglazed for increasing frictional forces between inferior bowl contact ridge  30  and a contact surface upon which container assembly  80  is placed, thus reducing the tendency for outer bowl member  82  to slide along the contact surface. 
   Inner vessel member  84 , as is illustrated in  FIGS. 14 ,  15  and  18 , is also an open-top bowl-shaped container being sized and shaped for nested placement in outer bowl member  82  and is therefore, preferably fashioned to also have a substantially circular horizontal cross-section or approximate a circular shape when viewed from a top plan view as specifically illustrated in  FIG. 14 . Inner vessel member  84  primarily functions to retain or contain a temperature-controlled substance. The temperature-controlled substance, as indicated above, may include foodstuffs, medicinal or medical products, plant products, pet products, and other similar temperature-dependent items. 
   As further noted, inner vessel member is also preferably constructed with porous or breathable materials and generally comprises inner vessel surface  42  as illustrated in  FIGS. 14 and 15 ; outer vessel surface  44  as illustrated in  FIG. 15 ; superior perimeter flange  46  as illustrated in  FIGS. 14 and 15 ; superior vessel contact seat  48  as illustrated in  FIGS. 14 and 15 ; and inferior vessel portal ridge  50  as illustrated in  FIGS. 15 and 15(   a ). Superior perimeter flange  46  is sized and shaped to snug down or snugly rest atop superior bowl support rim  26 . The junction between superior perimeter flange  46  and superior bowl support rim  26  is snug or gapless for preventing the passage or permeation of vapor through gaps between the junction point of superior perimeter flange  46  and superior bowl support rim  26 . Superior vessel contact seat  48  is spatially-located inwardly adjacent to superior perimeter flange  46  and has a critical contact seat perimeter dimension, which dimension includes inner seat perimeter  49 ( a ) and outer seat perimeter  49 ( b ). Inner seat perimeter  49 ( a ) and outer seat perimeter  49 ( b ) thus have a certain seat width measured therebetween, as is illustrated in  FIG. 14 . 
   As inner vessel member  84  and outer bowl member  82  nest together in the described fashion, outer vessel surface  44  is sized and shaped to rest in gapped relation to inner bowl surface  22  as shown in  FIG. 18 , thus creating a container cavity for retaining vapor and the temperature-maintaining matter. Inner vessel surface  42 , outer vessel surface  44  and superior perimeter flange  46  are further defined by preferably comprising a hydrophilic, vapor-impervious, glazed coating, preferably of a type that functions to prevent passage or permeation of vapor or water-based solution through the vapor-impervious glazed coating, thus forcing vapor, permeating from the volatile temperature-maintaining matter, through unglazed inferior vessel portal ridge  50 , which then may further permeate the structural space sandwiched between inner vessel surface  42  and outer vessel surface  44 . Further, the vapor may then exit the structural space between inner vessel surface  42  and outer vessel surface  44  via superior vessel contact seat  48 . Inner vessel surface  42 , outer vessel surface  44  and superior perimeter flange  46 , when provided with a vapor-impervious glazed coating, thus form a porous conduit through which vapor may permeate. 
   As indicated, a significant aspect of the present invention is that inner vessel member  84  is sized and shaped for placement within the interior of outer bowl member  82  in a removable stacking relationship, as is illustrated in  FIGS. 11 and 18 . In other words, inner vessel member  84  may be stacked inside of outer bowl member  82  and then removed, when needed, for independent usage. In this last regard, superior perimeter flange  46  may further comprise at least one outwardly extending handle  47  for facilitating the removal of inner vessel member  84  from outer bowl member  82 . Preferably, superior perimeter flange  46  has two outwardly extending handles  47  opposite one another for symmetry and for safety reasons as shown in  FIGS. 11 ,  14 ,  15  and  18 . Symmetrical handle structure contributes to a more aesthetically pleasing appearance and in most cases two handles are safer insofar as a user&#39;s left and right hand may more easily lift two handles opposite one another. Outwardly extending handles  47  thus provide for easy grasp and removal of inner vessel member  84  from outer bowl member  82 . 
   Lid member  86  is provided being sized and shaped for seatedly enclosing inner vessel member  84  and is further fashioned to have a substantially circular horizontal cross-section or approximate a circular shape when viewed from a top plan view as specifically illustrated in  FIG. 12 . Lid member  86  has inner lid surface  62  as illustrated in  FIGS. 13 and 13(   a ); outer lid surface  64  as illustrate  11 ,  12 ,  13  and  18 ; superior lifting protrusion  66  as illustrated in  FIGS. 11 ,  12  and  18 ; and inferior lid contact surface  68  as illustrated in  FIG. 13(   a ). Inferior lid contact surface  68  has a lid contact surface perimeter of a critical contact surface perimeter dimension, which dimension includes inner lid perimeter  69 ( a ) and outer lid perimeter  69 ( b ). Inner lid perimeter  69 ( a ) and outer lid perimeter  69 ( b ) thus have a certain lid contact surface width measured therebetween, as is illustrated in  FIG. 13(   a ). 
   Inferior lid contact surface  68  is sized and shaped to snug down or snugly rest atop superior vessel contact seat  48 . The junction between superior vessel contact seat  48  and inferior lid contact surface  68  is snug or gapless for preventing the passage or permeation of vapor through gaps between the junction point of superior vessel contact seat  48  and inferior lid contact surface  68 . Further, the measured width between inner lid perimeter  69 ( a ) and outer lid perimeter  69 ( b ) is less than the measured width between inner seat perimeter  49 ( a ) and outer seat perimeter  49 ( b ). More precisely, inner lid perimeter  69 ( a ) is substantially the same shape and dimension of inner seat perimeter  49 ( a ), but outer lid perimeter  69 ( b ) has a lesser dimension (though same shape) as outer seat perimeter  49 ( b ). Thus the outer edge of inferior contact surface  68  terminates at a point intermediate the measured width between inner seat perimeter  49 ( a ) and outer seat perimeter  49 ( b ), thus exposing superior contact seat  68  of enclosed inner vessel member  40  to the air or creating a contact seat vent  52  as illustrated in  FIGS. 11 and 18 . 
   Inner lid surface  62 , outer lid surface  64  and superior lifting protrusion  66  are each further defined by preferably comprising a hydrophilic, vapor-impervious, glazed coating, preferably of a type that functions to prevent passage or permeation of vapor or water-based solution through the vapor-impervious glazed coating, thus forcing vapor, permeating from the volatile temperature-maintaining matter in the container cavity, through unglazed inferior vessel portal ridge  50 , through superior contact seat  48 , and either into inferior lid contact surface  68  or into the air adjacent container assembly  10  via contact seat vent  52 . 
   Inner lid surface  62  and outer lid surface  64  preferably define an ellipsoidal upper shell for increasing the internal volume of the enclosed inner vessel member as shown in  FIGS. 13 and 18 . By thus increasing the internal volume of the enclosed inner vessel member  84 , users are enabled to place more voluminous temperature-controlled foodstuff or other substances therein. 
   Second Alternative Embodiment 
   A second alternative embodiment of the present invention concerns a container assembly similar to container assemblies  10  and  80  save for the amount of glazing applied to inner bowl surface  22  and outer bowl surface  24 . In the second alternative embodiment, an inner bowl surface  92  and an outer bowl surface  94  are left unglazed as is shown in  FIG. 19 . By leaving inner bowl surface  92  and outer bowl surface unglazed in varying extents (not illustrated) the manufacturer can tailor the container assemblage to cultural or situational norms. For example, a culture that is not heavily dependent upon refrigeration for its preservation needs, may desire a container assemblage with more breathability or porosity to increase the efficiency of the cooling/heating function of the container assemblage while downplaying the need for an aesthetically pleasing container assemblage, as is embodied in a somewhat thoroughly glazed assembly. It is thus contemplated that different consumers will desire different degrees of surface glazing, which the second alternative embodiment accommodates. 
   Method for Maintaining Container Contents in a Desired Temperature 
   The method of maintaining a temperature-controlled substance in a desired ambient temperature comprises the steps of (1) providing outer bowl member  20  or  82  as described herein; (2) placing temperature-maintaining matter as described herein (such as ice-Water solution  100 ) into outer bowl member  20  or  82 ; (3) providing inner vessel member  40  or  84  either with inner bowl surface  22  or  92  and outer bowl surface  24  or  94  as described herein; (4) placing a temperature-controlled substance into inner vessel member  40  or  84 ; (5) nesting inner vessel member  40  or  84  with placed temperature-controlled substance into outer bowl member  20  or  82 ; (6) providing lid member  60  or  86  as described herein; and (7) enclosing inner vessel member  40  or  84  with lid member  60  or  86  for maintaining the temperature-controlled substance in the desired ambient temperature. Naturally outer bowl member  20 , inner bowl member  40  and lid member  60  are used in tandem with one another while outer bowl member  82 , inner bowl member  84  and lid member  86  are used in tandem with one another. 
   Discussion of Preferred Materials 
   Ceramics art is ancient and has been used in many types of products ranging from simple utilitarian products to mass storage containers for wines and grains to highly sought-after ornamental treasures like service sets from Roman, Chinese and English artisans. Typically, ceramics are regarded as dense, hard, extremely strong, functional shapes that fit the given need of the user. Of the various types of ceramic, including generic ceramics found in everything from cabinet pull knobs and electric wire insulators to optical glass fibers, fine china and keepsakes such as dolls and figurines, the preferred materials for the present invention comprise ceramics that have been developed for their porous natures. These types of ceramic are typically referred to as hydrophilic or “water loving” and will provide capillary wicking and transport of water-based solutions in the event the ceramic contact surface comes into physical contact with a water-based solution reservoir. A porous ceramic is akin to many natural substances such as plants, soils, rocks, bricks and bone. Such natural materials have interstitial crevices and pathways (pores) that allow liquids and gases to mix, migrate and flow. It is this unique porous structure of the material that makes it the preferred material for the construction of the present invention. 
   Early porous ceramics were developed from high temperature porcelain “bisqueware,” which is more commonly known as “fired” but unglazed ceramic used in fine china. Other common compositions called for lower firing temperatures associated with talc/clay mixtures to produce a similar porous structure. Modern day porous ceramics are usually fabricated from either porcelain or Alumina bodies. Preferably, the porous ceramic utilized in the present invention should be engineered as an “open cell/pathway” ceramic, which means that the pores and pathways are interconnected and interlinked to provide a complete flow pathway throughout the material for permeating or migrating vapors or water-based solution. 
   Unlike porous materials developed from plastics that are hydrophobic (water hating), ceramics are naturally wettable and hydrophilic. The tough durable nature of a fired porous ceramic further makes it the preferential material of choice. Unlike porous metals that may oxidize or leak, porous ceramics are generally inert and can be produced with very consistent and uniform pore structures. Further, structures and devices fabricated from thick-walled porous ceramics tend to be more durable and therefore can withstand punishment from ordinary wear and tear associated with serving dish-ware and thus porous ceramics are the preferred material. 
   As indicated, the preferable porous ceramic material chosen to construct the present invention should comprise hydrophilic or water accepting materials. The term “hydrophilic” refers to those materials, such as porous ceramics and metals that have a natural ability to fill pores by capillary action. This means the pores and channels of the preferred porous ceramic will have a highly charged pore surface that will attract and bond the polar molecules of water vapor or other polar vapors of temperature-maintaining matter used. 
   Further, the pore size of a porous ceramic is of critical importance because it directly affects the ceramic&#39;s air entry value or “bubbling pressure” and hydraulic conductivity. The air entry value is the pressure at which air will break through a wetted pore channel. The hydraulic (liquid) conductivity of a porous ceramic is a measure of the rate at which a ceramic material of known thickness may conduct liquid from one surface to an opposing surface under a known pressure. The hydraulic conductivity will vary with the type of pore fluid used (generally water). The effective pore size is determined by the minimum orifice within a channel or pore. These properties that are determined by pore size are intrinsic to ceramics and to all other porous materials. How a porous material behaves in any application is directly related to these pore properties and the material from which it is made. As the type of porous ceramic may differ depending on the specific application, it is recommended that the user consult a reputable porous ceramics manufacturer regarding the specifications of the proper porous ceramic for a given application. 
   It is further noted that most porous materials will change their volume with changes in moisture content. Because physical changes are brought about by changes in moisture content that may cause deterioration of a material and shorten its useful life, the tough durable nature of a fired porous ceramic further makes it the preferential material of choice. Further noted is that the temperature-maintaining characteristics of the present invention will differ depending on the amount of ice-water solution  100  the user places into outer bowl members  20  or  82 . If the user places sufficient amount of ice-water solution  100  into outer bowl member  20  or  82  such that inferior vessel contact ridge  50  comes into contact with the water-based solution, then adsorption of ice-water solution  100  will occur. 
   As long as water in its three states (solid, liquid, gaseous) is in the environment outside a material, it can be referred to as bulk water and its behavior is predictable on the basis of the normal properties of water. When it comes into contact with the surface of a material (for example when contacting unglazed inferior vessel portal ridge  50 ), however, its behavior is no longer predictable on the basis of its bulk properties. By way of illustration, by placing a drop of water on the surface of a porous brick, the water not only spreads on the surface but also enters the material, disappearing into the pores and leaving only a damp spot at the surface. If the same brick had been pre-treated with a hydrophobic glazed coating, the drop would remain on the surface. The different behavior of water in the two environments demonstrates the mutual influence exerted by the water and the surface of the material. 
   The first layer of atoms at any surface is at an energy state different from that of the underlying atoms within the material owing to an imbalance of forces. This results in what is described as interfacial energy or surface energy. In liquids it is called surface tension. The surface energy, as would be expected, varies with the nature of the surface as defined by the particular atoms at the surface and their interactions with neighboring atoms. Surfaces that are wetted by water often have an attraction for water molecules. This results in a process of adsorption whereby a definite amount of water will be held at equilibrium with the relative humidity of the environment. Where the material has a very low surface area (non-porous material) the total amount of water held by the material will be insignificant. Where the material is porous, however, and the total surface area is large, the amount of water held will be relatively large. 
   Should inferior vessel portal ridge  50  come in contact with ice-water solution  100 , the wetting process that follows involves capillary conduction, where suction acts as the driving force, and is quite different from water vapor diffusion. The process of wetting by liquid water involves water proceeding as a front involving a very steep gradient of moisture content. The advance of this front into the porous material is characteristic of the material (each material having its rate constant) and decreases with the square of the distance traveled. It will take approximately four times as long to pass through a sample 2 inches thick as it will a sample 1 inch thick, both of identical material. When the wetting front passes through the material, thus saturating it, the flow ceases unless a head or pressure difference is applied on the source of water. The flow that follows through the saturated material involves a different process, being controlled by the permeability and the hydraulic pressure difference. Wetting by contact with liquid water (as would be the case in situations where the user overfills outer bowl member  20  or  82  with temperature-maintaining matter above the line of demarcation) would produce a very large moisture content gradient, in contrast with wetting by vapor unless the latter also involves a temperature gradient. 
   Discussion of Testing Data 
   In an effort to obtain initial stability data for butter samples stored in the present invention, Medallion Labs of Minneapolis Minn. tested the present invention in the following manner: Butter samples were stored at room temperature (approximately 70 Fahrenheit) in the present invention or container assembly. Each container assembly was filled with cold tap water to the fill line as marked on the inner bowl surface. Butter samples were pulled for analyses at 0, 4, 8, 11, 15, 18 and 21 days of storage. Aerobic plate counts were run to check for microbial growth; peroxide values were run as a marker of oxidative rancidity; and free fatty acids were run as a marker of hydrolytic rancidity. 
   No spikes in any of the analytical markers were evidenced during the testing process. No quantifiable microbial growth was detected in the butter samples tested in this study over the 21 day period. The increase in the peroxide value after four days of storage may have resulted from the photoinitiation of oxidative rancidity on the surface of the butter. This would be associated with the butter samples being exposed to light. The results from the described testing are summarized in Table No. 1, as found below. 
   
     
       
             
             
             
             
             
             
           
             
             
             
             
             
             
           
         
             
               TABLE NO. 1 
             
             
                 
             
             
                 
               Free Fatty 
               Peroxide 
               Aerobic 
               Mesophilic 
               Mesophilic 
             
             
               Days of 
               Acids 
               Value 
               Plate 
               Anaerobic 
               Aerobic 
             
             
               Storage 
               (g/100 g fat) 
               (Meq/kg) 
               Count 
               Spores 
               Spores 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               0 
               0.276 
               0.227 
                 
               &lt;10 
               &lt;10 
             
             
               4 
               0.217 
               0.359 
               &lt;10 
               &lt;10 
               &lt;10 
             
             
               8 
               0.213 
               0.343 
               &lt;100 
             
             
               11 
               0.244 
               0.366 
               &lt;10 
             
             
               15 
               0.177 
               0.383 
               &lt;100 
             
             
               18 
               0.158 
               0.365 
               &lt;100 
             
             
               21 
               0.164 
               0.410 
               &lt;100 
             
             
                 
             
           
        
       
     
   
   While the above description contains much specificity, this specificity should not be construed as limitations on the scope of the invention, but rather as an exemplification of the invention. For example, the porous ceramic material need not be hydrophilic. So long as the container assembly comprises hydrophobic porous ceramic material and allows permeation of vapor from the temperature maintaining matter (similarly of a hydrophobic nature) or wicking action of the same, the porous ceramic material successfully fulfills its vapor (or liquid) conduit purpose. In this regard, should a hydrophobic porous material be used, the temperature-maintaining matter should accordingly have hydrophobic properties and the vapor-impervious glazed coating, while preferably hydrophobic, should be hydrophilic in cases where the user prefers to utilize hydrophobic temperature maintaining matter and hydrophobic porous ceramic. 
   Furthermore, the container assembly need not be in a lidded state for maintaining temperature-controlled substances at a desired temperature. For example, when users wish to gain entrance to the inner vessel member for utilizing or consuming the temperature-controlled substance, the lid must be removed, thus exposing the temperature-controlled substance to the air adjacent the container assembly. The container assembly, however, continues to be operable insofar as the temperature-maintaining matter and the described permeating vapor continue to maintain the temperature-controlled substance at a desired temperature without the lid member in place atop the inner vessel member. In this regard, it is contemplated that the present invention may be easily adapted for continual serving purposes, where the lid member is removed for prolonged periods of time or left off entirely. In this regard, the present invention may readily be adapted for other uses. For example, the present invention may foreseeably be constructed of terra cotta or terra cotta-type material and utilized as a pet watering bowl. 
   Accordingly, although the invention has been described by reference to a preferred embodiment, it is not intended that the novel device be limited thereby, but that modifications thereof are intended to be included as falling within the broad scope and spirit of the foregoing disclosure, the following claims and the appended drawings.