PMG Cased Photographs: Tintype

Category:Photographic Materials
Category:Photographic Processes
Category:Materials and Treatment
Category:Preventive Care
Category:Environment
Category:Housing
Category:Bibliography
Cased Photographs. Including daguerreotypes, ambrotypes and tintypes was published as Chapter 2 of the The Photographic Materials Conservation Catalog in 1998. This printed information has served as basis for this wiki page, and current information has being added as necessary. 
Back to Cased Photographs See also Ambrotype Plates and Daguerreotypes
==Tintype Plates==
===Tintype Process===
 Tintypes are direct positive photographs produced on a lacquered iron 
Usually both sides of the metal plate were coated with the black (or brown) pigmented lacquer (sometimes called "japanning" or "Japan varnish"). One side of the plate is subsequently coated with iodized collodion. The wet collodion layer is then sensitized, exposed and developed. Physically-developed silver particles form the image highlights; this image silver was made to appear lighter in color by using diluted developers, development retarding agents, whitening agents (such as mercuric chloride) or cyanide fixers. Against the dark lacquered plate, the image appears as a positive. After development, the collodion image is fixed, dried and varnished. Hand-coloring may be applied before varnishing. 
The images are laterally reversed. Multiple images of the same subject could be produced with a multiple-lens camera, such as a carte-de-visite camera. 
Tintypes may be cased, as with ambrotypes and daguerreotypes, but more commonly they are found completely unhoused or in a paper window mat. Tintypes are often found mounted in specially manufactured tintype albums. Small tintypes were sometimes mounted in jewelry. 
The tintype process and its variants were used well into the twentieth century. Later versions of the process used gelatin silver emulsions on both lacquered metal and black paper supports. Refer to PMCC Photographic Process Tintype also.
===Tintype Condition===
Tintype Iron Support 
All types of metal supports are subject to mechanical distortion from bending or other mechanical working. The thin, flexible iron sheet of the tintype is particularly vulnerable to folding and bending, which frequently results in damage to overlying layers. 
Rust (iron oxide) is the most serious deterioration encountered on tintypes. 
This may occur at the edge of the plate, where the plate is more exposed to the environment. Alternately, cracks and losses in the pigmented lacquer, collodion and varnish layers caused by mechanical distortion and physical damage (scratches, folds and bends) result in exposure of the iron plate. 
Rust formation will lead, in turn, to further losses in the overlying layers. Note that rust, unlike other metal corrosion products, is generally not stable or protective against further corrosion. Dust can contribute to the corrosion of the iron support by retaining moisture and other corrosion initiators. 
A variant of iron corrosion is filiform corrosion that appears as irregular fine lines of corrosion products below the overlying layers. Tiny quantities of concentrated electrolyte solution formed by contaminants such as iron chlorides under the black lacquer layer move forward by capillary forces.
This is generally seen as a series of raised trails under the image that are especially noticeable in raking light. The "head" of the trail is the site of active corrosion; it moves through the iron support, leaving behind a trail of corrosion products in its path. This type of corrosion appears active only in environments with relative humidity above 58%. 
Iron oxides are more transparent to X rays than is iron. This difference could be used to determine the extent of corrosion that has occurred under the image and lacquer layers. 
Tintype Pigmented Lacquer Layer
The iron support of the tintype was coated (usually on both sides) with a black or brown lacquer that frequently contained a combination of linseed oil (or mastic or copal resin), asphaltum and pigment. This was baked onto the iron surface. Filiform corrosion may occur beneath this lacquer coating. 
The lampblack used in some coating formulations can promote corrosion of iron. 
Tintype Collodion Image-carrying Layer 
Collodion film is a form of cellulose nitrate produced from a solution of pyroxylin (cotton treated with mineral acids) dissolved in ether and alcohol. Collodion is soluble in many organic solvents. 
Collodion may be chemically unstable, particularly if excess alcohol was used in preparing the solution. These influences may result in collodion layer cracking or flaking. Collodion may yellow and become more opaque with age, causing a decrease in image contrast. Unvarnished collodion is extremely susceptible to mechanical abrasion.
Tintype Silver Image
The physically developed silver particles of tintypes are larger than the colloidal photolytic silver particles typical of printing-out processes. 
The silver images of tintypes, if properly processed, do not generally fade or discolor. However, tintypes may exhibit silver corrosion, particularly if the plate is unvarnished. Residual processing chemicals in the collodion layer, especially sodium thiosulfate, may cause staining and fading of the silver images. 
Tintype Paint/pigment Components 
Paints, usually watercolors and gouache, are applied on the tintype surface after treatment with a suitable wetting agent, such as ox-gall. Colorants are sensitive to light, moisture and abrasion. "Shell gold" (metal powder in oil or gum arabic solution) was used to highlight selected image areas, such as buttons and jewelry. 
Tintype Varnish 
Clear varnishes were used as protective coatings for all photographs employing collodion image-carrying layers; white shellac, dammar, sandarac and copal were commonly used resins. The varnish saturates the image by increasing gloss, and protects the underlying collodion layer and its silver image from physical damage and chemical deterioration. Tintype varnishes are applied as "spirit varnishes" which have a small amount of varnish resin dissolved in a solvent. The varnish was flowed onto the tintype surface, forming a film considerably thinner than a brushed varnish. 
Varnishes may lose gloss, become discolored, develop crazing or flaking, or accumulate dirt and grime. Deteriorated varnish may damage or obscure the underlying image layer. The abrasive nature of dust can scratch the varnish layer during handling. 
Research has shown the collodion/varnish interface on tintypes to be an intermingled zone rather than a discrete separation. The solubilities of collodion and the varnishes are often very close, and the collodion is very easily abraded, so it is likely that any attempt to remove a discolored varnish would also damage the collodion image-carrying layer.
 
===Tintype Preservation===
Temperature 
Heat alone is not a primary determinant of deterioration for tintypes. Cycling temperatures may produce interlayer cleavage of weakly adhered layers due to differences in dimensional response. High temperatures will accelerate deterioration of inherently unstable collodion and varnish layers. Additionally, high temperatures may lead to loss of moisture and desiccation of paper and case components. Lower storage temperatures will retard deteriorative processes of paper components and collodion binders but will not dramatically benefit either the silver image or the iron support. There is no reason tintypes cannot be housed in RH-controlled low-temperature storage areas. (These facilities must be equipped with appropriate transition climates to avoid transitory high humidity conditions on removal to normal temperature areas.) 
Relative Humidity
Atmospheric moisture accelerates rust and filiform corrosion on the iron supports. High humidity may accelerate the deterioration of inherently unstable collodion. Tintypes without cases may benefit from storage conditions below 40% RH. For a mixed collection of tintypes and cased photographs, 40% RH seems the best compromise condition. If possible, minimize the difference between the humidity conditions in the storage area and the areas where the objects are used for reference and display. 
Environmental Pollutants
Pollutants (especially sulfur and nitrogen compounds) can cause deterioration of the collodion silver images of tintypes, especially unvarnished plates. A varnished tintype that is well boxed will be relatively free from harm by airborne pollutants. However, the source of corrosion-inducing pollutants may be the original housing materials. These should be isolated from the plate, if possible. 
Light
Light is damaging to the natural resin varnishes used on tintypes. The pigments used for hand-coloring are frequently quite fugitive. The paper components of the packages may also be light-sensitive. 
Storage Containers for Tintypes
Cased tintypes may be housed in custom-made boxes as described above for ambrotypes and daguerreotypes. Tintypes in original paper mats may be over-matted in high-quality matboard window mats and stored in print boxes. 
Unhoused tintypes may also be matted. One approach to securing the plate for matting is described in the Handling Mat for Tintypes (entry below). Plates housed in this way can be fixed into a conventional window mat with a backboard and stored in a print box. 
For a large collection of uncased tintypes that have no original paper mats, a novel storage method has been suggested by contributors M. Fischer and A. Robb. This is an adaptation of a common technique used by archaeological conservators. Iron and other metals are kept in a low-relative-humidity environment by placing them in airtight food containers (such as Tupperware or Rubbermaid) containing preconditioned silica gel desiccant to control the relative humidity. This technique would be particularly useful for tintype collections kept in historic house museums that cannot maintain low relative humidity. This housing also has the benefit of isolating the collection from harmful atmospheric pollutants. Use a good-quality plastic container, such as one made of polyethylene that has passed the Photographic Activity Test. 
The amount of desiccant used is determined by the volume of the container. 
The silica gel is packed into polyester netting or a pierced polyethylene bag. A humidity indicator card should be placed in the box so that the relative humidity levels can be monitored. The quality of the seal of the container, the number of times the box is opened, and the ambient humidity when the box is sealed will all effect the period before reconditioning of the silica gel is necessary. While this storage technique has not been tested, it shows promise and warrants testing. 
Handling Mat for Tintypes
Outline the exact shape of the plate at the center of two sheets of high-quality 2-ply matboard that are approximately three times the height and width of the plate. Cutting freehand, create bevel apertures in both sheets that follow the plate outlines precisely; the bevel should be exaggerated to provide a lip that will catch and hold the plate in a channel between the two sheets, as in the diagram on the previous page. Use 3M Double-sided Film/Tape No. 415 to firmly attach the cardboard sheets together, creating a tight channel in which the perimeter of the tintype plate is held. These units can be stored in boxes or be individually enveloped. For display, they can be hinged into a conventional 4-ply window mat and framed. 
Plastic Sleeves for Tintypes 
Unprotected tintype plates or plates mounted in decorative paper mats may be inserted into a plastic sleeve with a high-quality 2-ply matboard insert as a stiffener and a humidity buffer. Polyester, polyethylene and polypropylene are suitable plastics. Plates with flaking collodion binder or friable hand-coloring media should not be put in plastic sleeves. 
The use of food-grade polyethylene "zip-lock" bags may be considered as an inexpensive and effective protective container for tintypes. Appropriate tests should be carried out on the specific product used. Sheet-form silica gel might be included as a desiccant. 
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===Tintype Treatment===
 In the following section, it is assumed that all treatments will be carried out by qualified conservators familiar with the materials and characteristics of the objects they are treating. No treatment indications given here can be considered safe for any object without suitable spot testing, careful observations and skilled, judicious application. 
Tintype Flattening
Some conservators have found that it is possible to flatten bent tintypes by burnishing the reverse with a smooth tool. Care must be taken to protect both front and reverse surfaces, perhaps with polyester film. Other conservators have successfully reduced the distortions of badly bent plates in a press, first sandwiching the plate between sheets of polypropylene and many layers of blotter; no visible damages were noted in the overlying layers when observed under magnification. However, it may be that overlying varnish and collodion layers are weak or cracked in these bent areas; flattening the tintype may exacerbate the damage. 
Contributors M. Fischer and A. Robb, while testing various treatments suggested for tintypes, found that flattening generally led to damage in the binder layer due to its extreme brittleness at room temperature. Their testing found that heating to increase the flexibility of the varnish layer during flattening does not greatly aid in the procedure. They found burnishing to not be particularly effective and to cause abrasions on the image layer. Planar deformations can be left untreated and the (distorted) plate can be supported in a custom sink mat housing. 
Tintype Iron Support - Reduction of Rust 
"Rusted iron seems to be the worst possible thing conservators encounter." (Brown et al., p. 137) Unlike other corrosion products, rust does not serve as a protective barrier for the uncorroded iron beneath it. Corrosion occurs in areas exposed due to damage, along the exposed edge of the plate, and even under the black lacquer layer itself producing blind cleavage. 
In treating iron corrosion, it is imperative to reduce the quantity of accumulated rust to a minimum before proceeding with any passivation, consolidation or coating steps. The removal or isolation of chloride contaminants is especially important since iron chloride is hygroscopic and produces a self-catalysed corrosion action. Chloride-induced corrosion is recognizable by its bright orange color. The presence of chlorides lowers the relative humidity threshold necessary for active corrosion from 60% to 40%. 
The only suitable technique for rust reduction on tintype supports is mechanical removal with small instruments. (Rust reduction with enzyme agents and complexing agents has been reported, and may eventually prove useful in the treatment of rusted tintypes.) General problems with mechanical reduction include the fact that it will not remove all the rust and may also cause the loss of flaking sections of the collodion image-carrying layer. In addition, mechanical removal of rust exposes uncorroded iron that must now be protected from further corrosion. The newly exposed iron is also quite shiny and may have to be treated in some way to make it less obvious. 
Fischer and Robb experimented with several mechanical instruments. They tested a scalpel blade and a micro-spatula on rust in an area of image loss; these resulted in evident scratches and removal was incomplete on a microscopic level. A softer material, such as a sharpened hardwood stick, resulted in incomplete rust removal but did not leave evident scratches. 
Tintype Iron Support - Passivation
The following section contains commentary and results derived from preliminary research on possible treatment options for tintypes carried out by contributors M. Fischer and A. Robb in 1992. None of the measures considered are current conservation treatment practices; they are offered here as a means of disseminating possible ideas for further research and testing.
Passivation is the production of an inert surface on a metal object that will not corrode in the future. 
One approach to iron passivation uses tannic acid. The treated area darkens to a black color a day or two after application. Preparation of the surface requires that the area be degreased and stripped -- difficult procedures due to the solubilities of the binder and varnish layers. The tannin must be used in an acidic solution (pH 2-3). Once the iron-tannate complex is formed, a coating should be applied. Proper equipment/protection must be in place when using tannic acid, a suspected carcinogen. (See Logan or Pelikán.) 
Pyrogallol (1,2,3-benzenetriol; 1,2,3-trihydroxybenzene; pyrogallic acid) can be used to form a protective blue/black pyrogallate layer on iron, similar in color to the lacquer. Care should be taken when using pyrogallol as the Merck Index considers it a poisonous substance. Two solutions of pyrogallol were tested by Fischer and Robb, one in water, the other in ethanol. The solvent carrier may cause problems to either the metal base, the lacquer or to the collodion binder layers. The method showed promising results; further testing of the material and technique is warranted. 
Rust-Oleum Rust Reformer is a commercial product made by the Rust-Oleum Corporation of Vernon Hills, Illinois and is available in hardware stores. It consists of tannic acid in a water-based vinyl acrylic copolymer emulsion with diethylene glycol methyl ether. The addition of the vinyl acrylic copolymer appears to act as a consolidant and a glossing agent. This combination of corrosion reduction and consolidant in one step may not be desirable; the action of tannic acid may be incomplete due to the premature drying of the consolidant. This appears to have been the cause of blistering in surface coating testing on aged samples. First, the areas of corrosion must be reduced as much as possible; the product can then be applied sparingly to areas of active corrosion. The result is a glossy black that resembles tintype lacquer. If not applied carefully, an excess could be left on the image layer. Testing of this product by Fischer and Robb gave very good results but long-term effects are not known; further investigation is warranted. 
Vapor phase inhibitors (VPIs) are compounds that invisibly coat the surface of a metal, excluding moisture and thus acting as a barrier. They require specific conditions to work, and little is known as to their effects on photographic images. Further testing may show them to be useful. One specific vapor phase inhibitor mentioned in Davis (p.18) that warranted testing was Daubert VCI, a paper impregnated with dicyclohexylammonium nitrate. 
Tintype Iron Support - Consolidation/Coating
The following section contains commentary and results derived from preliminary research on possible treatment options for tintypes carried out by contributors M. Fischer and A. Robb in 1992. None of the measures considered are current conservation treatment practices; they are offered here as a means of disseminating possible ideas for further research and testing. 
Since the entire iron support cannot be treated, corrosion reduction, passivation, consolidation, and coating treatments cannot fully stabilize the rusting tintype. They are really only local cosmetic treatments. Given this limitation, as well as the problematic nature of the materials used (solvents, water, heat), these consolidation treatments should be undertaken only after careful consideration. Rust reduction must be done before any attempt at consolidation, since corrosion products should not be trapped under the consolidant layer. The extent of the risks involved in using solvents, water and heat on tintypes is unresolved. 
It is important to dry and degrease a metal surface before coating. Heptane may be an acceptable degreasing agent. The use of gentle heating (under 40°C) may be an acceptable drying treatment, although this may be problematic due to the differing thermal coefficients of expansion of the tintype layers. 
Surface gloss factors may have to be considered when choosing a consolidant. 
Other critical factors may include aging characteristics and flexibility/strength of the consolidant.
Consolidants used by metals conservators on corroding objects include waxes, natural lacquers and synthetic products. Among waxes, microcrystalline wax is better than paraffin due to its superior water impermeability. 
Application of wax to a tintype may be difficult, especially in the delivery and the removal of any excess. 
Polyvinyl acetate and acrylic resins in various solvents were tested by Fischer and Robb as consolidants/coatings on a group of tintypes. Factors such as gloss, solubility of tintype components and degree of control were examined. 
*Polyvinyl acetate resins
**AYAT, 10% in toluene -- this gave the glossiest appearance.
**AYAF, 5% in ethanol -- severely flaking collodion emulsion may be locally consolidated with this solution; care must be taken as the collodion binder is soluble in ethanol. 
*Acrylic resins
**Harder resins:
***Acryloid B-48N, both 10% and 20% (w/v) in xylene/ethanol (1/1) were investigated as consolidants; both mixtures gave a matte appearance and worked well as consolidants. 
**Intermediate hardness resins:
***Acryloid B-67, 20% (w/v) in petroleum benzine gave a glossy surface, but not as shiny as that produced by the 10% AYAT in ethanol.
***Acryloid B-72; this resin was not tested.
***Acryloid B-82; this resin was not tested.
**Softer resins:
***Acryloid F-10, 10% (w/v) in petroleum benzine gave a matte appearance and seemed to work well as a consolidant. Consider that it is softer than the others tested and may not give the strength needed. 
Those consolidants dissolved in ethanol or part ethanol flowed more rapidly and easily, which allowed less control. Consolidants in toluene flowed most slowly, making the application more manageable. 
One source recommends applying graphite to the coated surface to form another protective layer that excludes moisture. 
The materials noted above should serve as a guideline to what is available and how they might be used on tintypes. No particular polyvinyl acetate or acrylic resin can be singled out as a panacea for treatment. 
Tintype Surface Dusting
Dry cleaning is important because it can reduce dirt and grime while avoiding the problems associated with wet cleaning. However, reduction of dust and grime is problematic due to the potential of scratching the varnish and/or binder layers by the action of the dust or the device used to remove the dust. Flaking and cracked binder and varnish layers further complicate dry cleaning. 
While brushing, apply pressure sparingly. Sometimes the electrostatic charge from the brush alone is enough to pick up any dust particles in sensitive areas. Brushing may not remove all of the imbedded dirt and grime. 
Squirrel-hair brushes are among the softest western brushes. They are softer than cotton swabs and are not very resilient. A less resilient brush may be desirable when working in sensitive flaking areas. Different shapes and sizes of brushes should be considered. 
When working with the brushes, one should work from the middle outwards. 
When working near cracks and flaking areas, hold the brush perpendicular to the damaged area to reduce any chance of contact. It may be advisable to work under a microscope when dealing with severely flaking tintypes. 
Fischer and Robb experimented with the use of erasers and eraser crumbs; they do not recommend their use for dry cleaning of tintypes. They also experimented with cotton swabs, aspirators and blowers; they felt these provided less control than brush cleaning. 
Tintype Surface Cleaning 
Cleaning with organic solvents or aqueous solutions has the potential to remove embedded dirt and grime that cannot be removed by dusting. However, the potential for damaging the tintype is greatly increased in comparison to dusting; the varnish, collodion binder and iron support might all be damaged. Water contributes to the corrosion of the iron support. Many organic solvents will solubilize the varnish, the collodion binder or both. Please use all proper environmental and personal Health & Safety measures when using organic solvents and alcohols: Wear appropriate personal protection equipment, use and dispose of materials safely. 
Note that tintypes were made in different ways by varying methods and materials, and that this variability makes any generalization concerning their solubility characteristics 
The issue of whether surface cleaning of a tintype with solvents or aqueous solutions should be attempted is unresolved. McCabe (1991) states that "Washing collodion plates can be very damaging and should not be attempted." 
Fischer and Robb also discourage cleaning with either organic or aqueous solvents. 
The choice of delivery method for the cleaning agent is another complicating factor in wet cleaning. Despite their abrasiveness, cotton swabs are most commonly used because of the swab's ability to pick up and retain dirt. The abrasive nature of cotton in this context cannot be understated. Often the swelling action of the cleaning solution can make the varnish and/or collodion surface more sensitive to abrasion. Fischer and Robb also observed that dark areas (that is, nonsilver areas) are especially sensitive to abrasion. 
Fischer and Robb have tested the following solvents and solvent mixtures for liquid cleaning of tintypes: water, ethanol, water/ethanol (1/1), water/ethanol (25/75), petroleum benzine, heptane, acetone, xylene, and toluene. It would appear from their testing that ketone and aromatic hydrocarbon solvents should be avoided. Water did not appear to harm these layers, but its use is problematic as far as the iron support is concerned. 
Alcohols and short-chained aliphatic hydrocarbons may have less effect on varnish and collodion layers but can still cause damage if wrongly applied or applied to sensitive areas. (Naphtha should be included in solvent testing.) 
Tintype Pigmented Lacquer Layer - Consolidation; Inpainting Losses 
Any attempt at consolidation, inpainting or removal of the pigmented lacquer will be greatly complicated by the presence of an underlying collodion image-carrying layer and albumen sublayer (see Ambrotype treatment entry with same name). Thus, it is important to determine if the lacquer has been applied directly to the collodion layer or is on the uncoated glass side of the support. Acryloid B-72 in xylene (15-20%) may be appropriate for consolidation of a lacquer layer adjacent to a collodion layer. Two or three applications may be necessary to effect consolidation. Heptane or petroleum benzine might also be tested as solvent vehicles for the consolidating resin.
If the damaged lacquer layer is located on the uncoated glass side of the support, consolidation with a local application of an appropriate adhesive will be simpler. Likely candidates for this are Klucel G (hydroxypropyl cellulose) in alcohol or Acryloid B-72 in xylene. 
Another possibility for lacquer consolidation is the use of a solvent chamber to deliver solvent vapors. Testing the safety of such a procedure may be difficult. 
A backing of acrylic black velvet may be used to reintegrate missing sections of lacquer without having to remove original material. 
Alternatively, a backing of good-quality black paper (Arches Cover Black, for example) along with an interlayer of Mylar Type-D (3 or 5 mil) provides the high gloss and blackness necessary for this type of minimal-intervention reintegration. The lacquer is generally an original component of the object, and this must be a consideration in any decision to remove and replace it. 
However, if deterioration is so severe that complete removal is judged to be the best treatment option, the black layer may be replaced by velvet, paper/Mylar or by re-painting the glass surface with an appropriate paint. 
Small losses to the lacquer have been successfully inpainted with watercolor or with acrylic resin paints. Acrylic resins may be dispersed in heptane or petroleum benzine for this purpose. Reversibility and compatibility with the existing coating must be considered. Refer to Photographic Materials Conservation Catalog (PMCC) -- Inpainting of Historic Photographic Prints for comments on specific inpainting materials. 
Tintype Collodion Image-carrying Layer - Consolidation 
The thin collodion layer on a tintype, if it is found to be in poor, unstable condition, will be extremely difficult to successfully consolidate. The possible presence of an albumen sublayer further complicates the approach. The usual caution conservators exercise in approaching treatment options must be doubled in these instances. Careful spot testing is imperative before consolidation can be undertaken. Weak gelatin and methylcellulose solutions (applied with a brush) may be used to readhere flaking collodion to its underlying glass support.
Alternatively, Acryloid B-72 in xylene may be used. It may be possible to disperse the acrylic resin in heptane or petroleum benzine for this purpose. One conservator has reported success using heat-activated PVA resin -- AYAF, 5% in ethanol. (Baas, 1982) In all cases, the application of consolidants should be considered irreversible. It may be possible to readhere flaking collodion with solvent vapor applied in a solvent chamber. Overall applications of varnish as a consolidation treatment are not recommended. 
Tintype Collodion Image-carrying Layer - Inpainting Losses
 There is little published research concerning the inpainting of ambrotypes and tintypes. 
Dry pigments mixed with an acrylic resin, such as Acryloid B-72 (soluble in nonpolar solvents), have been successfully used to inpaint ambrotypes. Consider dissolving the resin in heptane or petroleum benzine for this application. Klucel G (hydroxypropyl cellulose) and Soluvar Matte Varnish have also been suggested as inpainting media. An appropriate isolating layer should be used beneath all inpainting. Refer to Photographic Materials Conservation Catalog (PMCC) -- Inpainting of Historic Photographic Prints for comments on specific inpainting materials. One contributor reports successful use of pastel dust applied without any vehicle using a very soft bristle brush. The pastel dust can be removed, if necessary, with a nonpolar solvent or by simply blowing it away.
==Glossary==
*Alabastrine process -- a variant of the ambrotype process, using mercury chloride bleaching
*Ambrotype -- a collodion silver photograph on glass; a direct positive camera original
*Amphitype -- among other things, a process similar to ambrotype but using albumen
*Binding tape -- an alternate term for sealing tape
*Case -- a hinged box holding an ambrotype, or an American or British daguerreotype
*Clasp -- brass hardware on a case that secures the closure of the hinged case cover
*Collodion -- binder layer of ambrotypes, tintypes, and wet-plate negatives
*Collodion positive -- term used in Britain for ambrotype
*Cover glass -- protective glazing used on daguerreotypes, and some ambrotypes and tintypes
*Cushion -- cardboard, cotton fibre and textile pad fixed to the inside surface of the case cover
*Daguerreotype -- a photograph with silver image particles on a silvered copper plate
*Deliminator -- an alternate term for a metal mat
*Ferrotype -- an alternate term for tintype
*Gilding -- a step in daguerreotype processing in which gold is added to the image particles
*Hinge -- paper, leather or metal attachment between the case cover and tray
*Lacquer -- a pigmented paint layer, used on both ambrotypes and tintypes
*Lampratype -- a variant of the ambrotype process
*Mat -- paper or metal sheet with an aperture cut in its centre
*Melainotype, melanotype -- alternate terms for both ambrotype and tintype
*Package -- plate and housing components forming a sealed unit; may be cased or framed
*Pad -- an alternate term for cushion
*Pannotype -- a collodion positive, similar to a tintype, but on black waxed textile or leather
*Passe-partout (package) -- a daguerreotype housing format common in Europe
*Perfling -- an alternate term for retainer
*Pinchback -- an alternate term for preserver
*Pinch pad -- an alternate term for retainer
*Preserver -- for cased objects: brass foil that is folded around the edges of the plate package
*Relievo -- a variant of the ambrotype, in which the background image areas are scraped away
*Retainer -- velvet and cardboard strip lining the edge of the case tray
*Sealing tape -- strip adhered at the perimeter of a package and holding the components together
*Stereograph -- a two-image photograph which represents its subject three-dimensionally
*Tintype -- a collodion silver photograph on an iron plate; a direct positive camera original
*Tray -- the half of the case opposite the cover, which receives the package
*Union case -- a case made of an early thermoplastic material
==Bibliography==
===General===
*Angelucci, S.; P. Florentino; J. Kosinkova; M. Marabelli. "Pitting Corrosion in Copper and Copper Alloys: Comparative Treatment Tests." Studies in Conservation 23 (1978), pp. 147-156. 
*Austin, Michele C. "An Examination of Daguerreotype Brass Mats." University of Delaware/Winterthur Art Conservation Program, unpublished student research project report, 21 May, 1984. 
*Barger, M. Susan; Deane K. Smith; William B.White. "Characterization of Corrosion Products on Old Protective Glass, Especially Daguerreotype Cover Glasses." Journal of Materials Science 24 (1989), pp. 1343-1356. 
*Brown, Barbara. "Four-flap Enclosure ('Tuxedo' Case) Adapted for Housing Cased Photographs." Austin, Texas: Harry Ransom Humanities Research Center, unpublished presentation, September 1996. 
*Hendriks, Klaus B.; Brian Thurgood; Joe Iraci; Greg Hill. Fundamentals of Photograph Conservation: A Study Guide. Toronto: Lugus Publications, 1991. 
*Hendriks, Klaus B. CCI Notes 16/1: Care of Encased Photographic Images. Ottawa: Canadian Conservation Institute, 1995. 
*Hill, Jo. "Corrosion of Mats and Preservers on Case Objects." University of Delaware/Winterthur Art Conservation Program, unpublished student research project report, May 1991. 
*King, Chris. "My Grandmother Has One of Those -- Daguerreotypes, Ambrotypes, Tintypes -- Their Problems, Processes, and Care." Conference of Students in Art Conservation. April 10-12, 1978. Cooperstown, NY: Cooperstown Graduate Programs, 1978, pp. 82-97. 
*Krainik, Clifford; Michele Krainik; Carl Walvoord. Union Cases: A Collector's Guide to the Art of America's First Plastics. Grantsburg, WI: Centennial Photo Service, 1988. 
*Kusnerz, P.A. "Preservation of Case Photographs." Michigan Museums Review 7, no.4 (1973), pp.7-9.
*Longford, Nicola. "Stamped Vines and Verdigris: Uncasing the Mysteries of the Brass Mat." St. Louis: Missouri Historical Society, unpublished presentation, September 1996. 
*Rempel, Siegfried. "The Conservation of Case Photographs." Archivaria no. 3 (winter, 1976/1977), pp. 103-108. 
*Rinhart, Floyd; Marion Rinhart. "Miniature Cases for Daguerreian Art." In American Daguerreian Art. New York: Clarkson N. Potter, Inc., 1967, pp. 87-91. 
*Rinhart, Floyd; Marion Rinhart. American Miniature Case Art. Cranbury, NJ: A. S. Barnes and Co., 1969. 
*Smith, Brenda Lee. "Photographic Union Cases: The First Plastic Composite." Queen's University Art Conservation Program, unpublished student research report, 1994.
===Ambrotypes and Tintypes===
*Archer, Frederick Scott. "On the Use of Collodion in Photography." The Chemist 2 (March 1851), pp. 257-258. 
*Baas, Valerie. "Conservation of Tintypes." American Institute for Conservation - Photographic Materials Group, 2nd annual meeting, Milwaukee, 1982, unpublished presentation. 
*Baas, Valerie. "The Treatment of a Flood Damaged Ambrotype." American Institute for Conservation -- Photographic Materials Group, 3rd annual meeting, Chicago, February, 1983, unpublished presentation. 
*Barger, M. Susan. "Characterization of Deterioration of Glass Supported Photographic Images." Printing of Transcript Summaries. Second International Symposium: The Stability and Preservation of Photographic Images. Springfield, VA: Society of Photographic Scientists and Engineers, 1985, pp. 134-147. 
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Page information 
Date initiated: September 1998 
Contributors for wiki version: Luisa Casella, Amanda Maloney, Stephanie Watkins
Compiler for printed version (1998): John P. McElhone
Contributors for printed version (1998): Gary Albright, M. Susan Barger, Valerie Baas, Lee Ann Daffner, Deborah Derby, Tom Edmondson, Monique Fischer, Chris Foster, Lynne Gilliland, Marion L. Hunter, Jr., Wayne King, Barb Lemmen, Mark H. McCormick-Goodhart, Angela Moor, Ian Moor, Peter Mustardo, Debbie Hess Norris, Nancy Reinhold, Andrew Robb, Elena Bulat, and Annabelle Chabauty.
Edition copyright (1998): The Photographic Materials Conservation Catalog is a publication of the American Institute for Conservation of Historic and Artistic Works. The Photographic Materials Conservation Catalog is published as a convenience for the members of the Photographic Materials Group. Publication does not endorse nor recommend any treatments, methods, or techniques described within the chapter.
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