PMG Cased Photographs: Ambrotype

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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 Daguerreotypes and Tintype Plates

Ambrotype Plate

Ambrotype Process

Ambrotypes are direct positive photographs produced in the camera on a transparent or colored glass plate. The glass is coated with collodion (a cellulose nitrate solution), which is then sensitized, exposed and developed. Physically developed silver forms 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. After development, the image is fixed, dried and varnished. Placed against a dark background (fabric, paper, pigmented lacquer), the light colored silver image appears as a positive. Sometimes the collodion was left unvarnished. Paints or dry colours may have been applied before or after varnishing. An albumen substrate layer was sometimes used to improve the adhesion of the collodion to its glass support. The image-carrying layer may be on the surface of the glass closest to the viewer, in which case the image will be laterally reversed and the package will require a cover glass. These may be referred to as "double plate" ambrotypes. Sometimes the plate is positioned with the image-carrying layer on the interior side of the package; this corrects the image reversal and eliminates the need for a cover glass. These may be called "single plate" ambrotypes. The arrangement and treatment of the various layers inside the ambrotype package were subject to many variations. ("Ambrotype" originally referred to an American variant patented by James Ambrose Cutting. Other variants of the process were called alabastrine process, amphitype, lampratype, relievo.) Ambrotypes were sometimes made on blue-, red-, orange-, green- or purple-colored glass (the latter being called "Bohemia glass" or "ruby glass"). Ambrotypes made on dark-colored glass do not require a dark backing. One contributor observes that these plates are often unvarnished and, as a result, show more extensive silver image deterioration. Ambrotype plates may be adhered overall to another plate of glass with Canada balsam, a natural resin adhesive. (This is the subject of the Cutting patent.) In the relievo variant, all of the image-carrying layer representing the mid-tone background behind a portrait subject was scraped away. This allowed the figure to "float" on the dark field of the added backing and lent a sense of depth to the subject. Refer to PMCC Photographic Processes entry on Ambrotype (Positive Collodion) also.

Ambrotype Condition

Ambrotype Glass support
The glass used to make ambrotype plates was usually commercially available pane glass. There were some companies that sold "photographic" glass -- this meant that the glass was free of physical flaws and was relatively colorless, not that the glass had superior durability or corrosion resistance. Glass supports of all types are susceptible to physical damages such as breaking and chipping. Some glass formulations are chemically unstable due to a high flux content, especially those with a high ratio of sodium flux in proportion to the alkaline earth flux (calcium and magnesium oxide). Note that glass with a high sodium content produces a yellow-orange fluorescence under UV illumination, whereas glass with a higher alkaline earth content tends to produce orange-magenta fluorescence. See Katharine Whitman's section Glass in Photographic Materials for more details regarding glass history, manufacture, and repair. Also refer to the general Cased Photographs section for more information regarding the condition of nonadhered cover glass.

Glass corrosion is caused by inherent instability linked to unfavorable environmental conditions. Writing about the condition of glass in collodion wet-plate negatives, M. H. McCormick-Goodhart states, "The collodion and varnish coatings applied to the glass typically prevent the image bearing side of the plate from exhibiting the 'weathered' or 'weeping' glass appearance observed on daguerreotype cover glasses. Nevertheless, alkali leaching from the glass and diffusing into the collodion and varnish layers promote chemical changes in the coatings. The weakened coatings are prone to crazing, cracking, flaking and gradually increasing varnish saponification even though just a small fraction of the glass substrate is involved in the reaction. A hydrated 'silica-rich' layer forms at the original collodion-glass interface, and this layer may also contribute directly to the collodion's adhesion quality, because it is microporous and hygroscopic in nature." (McCormick-Goodhart, "Glass Corrosion . . .," 1992, p. 264).

Glass corrosion, leading to the accumulation of alkaline materials and silicates on the surface of the glass, is a major cause of deterioration in cased photographs. Unfortunately, the design of the cased photograph package encourages the type of corrosion in cover glass called "static weathering." In this process, the inner surface of the cover glass is exposed to a small enclosed air volume; this air is subject to transient periods of high or cycling relative humidity. The glass used in photographic packages should be checked regularly for signs of weathering corrosion. It may be easier to detect corrosion films by examining the glass by specular reflection. Look for:

  • early signs -- a faint surface haze or clouding;
  • more advanced states of "weeping" glass, including the presence of tiny droplets that lend a "greasy" or "soapy" feel to the surface; these are primarily amorphous sodium silicates (water glass) and have a high pH -- in the range of 10-14 (the presence of alkaline corrosion products may be detected by burnishing a pH indicator strip on to the affected surface);
  • needle-like crystals and incrustations on the inner surface of the glass - they may also have spalled off, leaving the crystals on the surface of the photograph below;
  • blister-like crystals that appear to have a small darker-colored core;
  • mold-like masses on the surface of the daguerreotype plate below, sometimes obviously associated with a spalled-off crystal corrosion product from the cover glass above; these have a "bead-and-thread" morphology reminiscent of Candida spp. but are entirely inorganic.

Refer to Barger; Smith; White (1989) for more information on cover glass deterioration. Refer to Katharine Whitman's section Glass in Photographic Materials for more details regarding glass history, manufacture, and repair, also.

Ambrotype 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. Unvarnished collodion is extremely susceptible to mechanical abrasion. The collodion binders of ambrotypes and tintypes may be chemically unstable, particularly if excess alcohol was used in preparing the solution. Ambrotype collodion layers may be chemically altered by glass corrosion at the glass-collodion interface (see above). All these influences may result in the collodion layer cracking or flaking. Collodion may yellow and become more opaque with age, causing a decrease in image contrast.

Image not in original PMCC published chapter. Ambrotype showing crack pattern of the collodion layer
Image not in original PMCC published chapter. Ambrotype (same as above) under reflected light

Ambrotype Silver Image
The physically developed silver particles of ambrotypes are larger than the colloidal photolytic silver particles typical of printing-out processes. Normally the silver images of ambrotypes, when properly processed, do not fade or discolor. However, they may exhibit silver corrosion, especially if the image is unvarnished. Residual processing chemicals in the collodion layer, especially sodium thiosulfate, may cause staining and fading of the silver images. One contributor has observed instances of ambrotypes which have converted to a bright yellow color.

Ambrotype Coatings (pigmented lacquer and clear varnish)
Pigmented lacquer (frequently made from lamp black pigment mixed in bitumen, asphaltum or linseed oil) was often used on the verso side of the clear glass support. Deteriorated lacquer may exhibit crazing and flaking, especially if it contains asphaltum. Deteriorated lacquer may also damage the collodion image layer if these layers are adjacent. Many ambrotypes have a clear varnish applied on the collodion image layer; white shellac, dammar, sandarac and copal were commonly used. The varnish saturates the image by increasing gloss, and protects the underlying collodion layer and its silver image from physical damage and chemical deterioration. Ambrotype varnishes are applied as "spirit varnishes" which have a small amount of varnish resin dissolved in a solvent. The varnish was flowed onto the collodion image surface, forming a film considerably thinner than a brushed varnish. Varnishes may be chemically altered by glass corrosion at the glass-collodion interface (see entry on same above). Deteriorated varnishes may exhibit discoloration, crazing, flaking or partial liquefaction (saponification). They may also damage or obscure the underlying image layer. Varnish layers can lose gloss and accumulate dirt and grime. Dust can scratch and abrade the varnish and binder layers during handling. The solubilities of the collodion image layer and the varnish are typically very similar, and the collodion is very easily abraded, so it is likely that any attempt to remove a discolored varnish will also remove some image-carrying layer.

Ambrotype Paint/pigment Components
Pigments may be applied to ambrotypes in several ways and using various binding media. If watercolors are used, these will require the addition of a suitable wetting agent, such as ox-gall. Paints may be applied over the image-carrying layer or behind the glass support. In the case of "flipped" plates, where the image is seen through the glass support, the hand-coloring applied to the image-carrying layer will be seen through the collodion silver image. 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.

Ambrotype Preservation

Cased photographs are composite artifacts having complex reactions to environmental conditions. Conditions that are optimal or innocuous for one component may be damaging to another. Environmentally induced deterioration processes in one component may cause the production of reaction products harmful to another component.

Cycling temperatures may produce interlayer cleavage of weakly adhered layers due to differences in dimensional response. High temperatures may cause desiccation and may promote the deterioration of inherently unstable collodion layers, lacquer and varnish layers. Lower storage temperatures will retard deteriorative processes of paper components and collodion binders but will not dramatically benefit either the silver image or the glass support. There is no reason ambrotypes 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
In all types of cased objects, high relative humidity will contribute to deterioration of unstable glass, as well as corrosion of metal supports, mats and preservers. The leather, paper and wood components of cases will swell and shrink with fluctuating humidity, and they may become embrittled at low humidity. Leather may be structurally weakened at high humidity. Relative humidity above 60% can sustain mold growth. The major driving forces behind glass corrosion are moisture and fluctuations in relative humidity. Water (from moisture in the air) interacts on an atomic level with the glass surfaces, initiating glass corrosion cycles. Glass is best maintained at moderate relative humidity (40-50%) without excursions to higher or lower humidity. High humidity may accelerate the deterioration of the inherently unstable collodion layers of ambrotypes. For a mixed collection of ambrotypes, daguerreotypes and tintypes, 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
Atmospheric pollutants can cause image deterioration in all types of cased objects. Sulfur dioxide, a common pollutant, can combine with oxygen and moisture to form sulfuric acid, which is particularly damaging to leather and paper. The silver image material of all cased photographs may be damaged by the ammonia, ozone, sulfur dioxide and nitrogen oxides generated in industrial environments. Sulfur and nitrogen compounds can cause deterioration of the collodion binder. (Most ambrotype plates are largely protected from contact with pollutants by the clear varnish layer.) Varnished ambrotype images that are well sealed and boxed will be relatively free from harm by airborne pollutants. However, the source of corrosion-inducing pollutants may be the materials composing the package and case. These should be removed or isolated from the image-carrying layer.

Silver image particles are generally not sensitive to light. However, as with all organic films, the collodion layer may be somewhat light sensitive. More seriously, light is damaging to the natural resin varnishes used on ambrotypes. The pigments used for hand-coloring and the textile components are frequently quite light sensitive.

Ambrotype Storage Containers
Cased photographs may be stored flat inside Solander boxes equipped with Ethafoam layers cut out to create cavities in which the cases fit snugly. The interior surface of the cavity is lined with a fine unbleached cotton textile to provide a nonabrasive surface. Alternately, custom-made individual matboard boxes of the clamshell or slipcase variety may be constructed to house cased ambrotypes. A four-flap enclosure adapted for housing cased photographs is used at the Harry Ransom Humanities Research Center. (Brown, 1996) This method is well-adapted for storing cased photographs on their edges, a measure recommended by some conservators to reduce glass corrosion-induced damage on the plate surface. Note that the inclusion of paper or cardboard inside containers provides some buffering capacity to modulate humidity fluctuations. Appropriately conditioned silica gel-containing sheets may be useful inside sealed containers for establishing stable humidity conditions. Materials containing molecular sieves (zeolites) can absorb pollutants that might otherwise produce deterioration in photographs.

Ambrotype 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.

Repair of broken glass Ambrotype plates
Ambrotypes with broken glass supports are difficult to repair for several reasons:

  • adhesives appropriate for glass repair may be reactive with the image components of the ambrotypes;
  • the edges to be mended require preparation with detergents or degreasing agents, which can have deleterious effects on image components;
  • it may be difficult to align the broken pieces without damaging the image layer or the pigmented lacquer;
  • repairs to broken glass supports are generally quite visible.

While there are several epoxy adhesives with a similar refractive index to that of glass, these are not generally suitable for ambrotype plate repair because accidental spread of the adhesive on the image layer during application cannot be safely removed. In addition, epoxies of this type generally have poor aging characteristics. Acryloid B-72 is a methyl methacrylate polymer which has been used successfully to repair glass plate negatives. While the bond formed is relatively weak and there may still be problems with removing excess, this adhesive is non-yellowing and reversible. If the mend must be removed, this can be done by either warming the joint sufficiently to soften the adhesive or using a non-polar solvent such as toluene. The ideal adhesive for repairing broken ambrotype plates would use a cleanup solvent that does not interact with the image-carrying layer or coatings, would be reversible and nonyellowing, would form a strong bond with glass and would match the refractive index of glass. See Katharine Whitman's section Glass in Photographic Materials regarding more current options for repairing glass photographic materials. In 1998, a consolidating resin, poly(2-ethyl-2 oxazoline), also called "Aquazol-50" or "P-Ox," looked promising, yet had not been tested in this application. (See Wolbers; McGinn; Duerbeck. Painted Wood: History and Conservation, Williamsburg, Va., Nov. 11-14, 1994, conference abstract, p. 40.)

In lieu of facility or application to repair broken glass plates, conservators and custodions may choose to only stabilize broken ambrotypes with passive measures -- by placing them in secure housing such as a custom sink mat.

Ambrotype Dusting
Dust may be removed from unvarnished collodion with a gentle stream of air from a rubber bulb syringe. These unprotected collodion surfaces are generally too fragile to tolerate any contact. Care should be taken not to dislodge the loosely bound hand-coloring. Varnished collodion that exhibits no signs of flaking or deterioration may be gently brushed to remove dust. Begin by brushing the glass surface with a long-haired soft brush while holding the plate firmly in one hand. Always brush from the center of the plate outward. This will reduce disturbance to damaged or abraded emulsion at the edges.

Ambrotype Cleaning
Ambrotype plates in good condition may sometimes be cleaned with water or organic solvents, although careful spot testing is imperative. Although immersion treatments have been reported, controlled application of cleaning solutions with cotton swabs or small brushes may be safer. Collodion and spirit varnishes are often soluble in alcohols and acetone. Deteriorated collodion may also be sensitive to water. Another consideration is the possible presence of an albumen substrate. If present, the albumen may absorb some water, causing the collodion emulsion to lift. Water may also cause blooming in the varnish layer. The presence of hand-coloring may be a further complication. This may have been applied to either the collodion image-carrying layer, underneath the varnish, or may be applied to the varnish surface. Alkaline solutions may alter the silver images of ambrotypes and should be avoided. Ketone and aromatic hydrocarbon solvents will risk solubilizing the varnish and collodion layers. Spot testing may establish that hexane (or the safer heptanes), mineral spirits, naphtha, petroleum benzine, trichloroethylene or trichloroethane can be used.

Ambrotype 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 sub-layer (see next entry below). 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 Inpainting of historic photographic prints for comments on specific inpainting materials.

Ambrotype Collodion image-carrying layer -- consolidation
The thin collodion layer on an ambrotype, if it is found to be in poor, unstable condition, will be extremely difficult to successfully consolidate. The possible presence of an albumen sub-layer 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.

Ambrotype 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. 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 non-polar solvent or by simply blowing it away.

Repackaging Ambrotype plates
For ambrotypes, two distinct approaches to repackaging exist, both based on historic daguerreotype designs evaluated by contemporary conservators. In one approach, the sealed ambrotype package contains no hygroscopic material, thus avoiding the presence of a reservoir of moisture inside the package that could drive the various processes of potential deterioration. This practice reflects the original format of cased daguerreotypes where no paper products, except the sealing tape, were included in the package. The other approach is to intentionally include a quantity of high-quality unbuffered matboard inside the sealed package (but not in direct contact with the image surface). This acts as a humidity buffer inside the package, helping to dampen relative humidity fluctuations inside the package. This practice reflects the original format of passe-partout packages (for daguerreotypes), which contain substantial quantities of paper, cardboard and adhesives. Whatever repackaging method is chosen, it is essential to ensure that all of the package components are well secured and will not slip or shift. Mechanical damage due to component slippage is a common phenomenon in cased photographs and avoiding future occurrences should be a major criterion in choosing a repackaging method.

Non-hygroscopic Package
This method uses a moisture-resistant barrier on the back of the package and does not introduce any hygroscopic material inside the package. A 5 mil Mylar backing is cut to be slightly smaller than the plate. If a barrier is required to prevent abrasion of the plate surface (see Cased Photographs Treatment: Brass entry), use a layer of a non-woven polyester web material. The package is closed with a moisture-resistant sealing tape (see Cased Photographs Treatment: Resealing entry). This style of repackaging has the advantage of adding little or no extra thickness and allowing the plate verso to be seen without disassembling the package. Marvelseal, a nylon/aluminum/polyethylene laminate, has also been used as an impermeable backing, but it lacks the advantage of transparency. If the plate is much smaller than the package, this method is difficult to use.

Humidity-buffered package variant
Modify the package described above by including a rectangle of matboard cut to precisely fit between the verso of the daguerreotype plate and the Mylar. Use high-quality matboard that does not contain alkaline pH-buffering compounds and that has been conditioned to an appropriate moisture level. Use a matboard thickness that will not add significantly to the package thickness if the plate is to be returned to a case.

Matboard Sink
This variant is most useful in the repackaging of passe-partout style packages and stereo-daguerreotype packages. A multi-layer matboard structure is made that holds the plate in correct register, provides maximum support for all edges and for the plate verso surface, and provides a separation between delicate surfaces and the glazing material. Use rectangles of high-quality, unbuffered 2-, 4- and 8-ply matboard cut larger than the finished package size to create a sink cavity for the plate. Use a layer of a nonwoven polyester web material to provide separation between the plate and any original package components that may cause abrasion or scratches. Adhere these layers with 3M Double-sided Film/Tape No. 415, starch paste adhesive, methylcellulose paste or PVA emulsion adhesive. It is essential to add only the minimum possible additional thickness to the package if it is to be returned to a case.

George Eastman House Housing
The Conservation Department at the George Eastman House has developed an elegant structure for housing unpackaged daguerreotype plates that combines some features of both approaches outlined above. This housing was inspired by a unique metal and paper housing associated with the American daguerreotypist Robert Cornelius. A matboard sink mat is made with cavities for the daguerreotype and for the cover glass. (See drawing below.) The daguerreotype cavity is slightly deeper than the total thickness of the plate, including its bevelled edges. The cover glass cavity should be the same depth as the glass thickness. A 5-mil Mylar cradle holds the edge of the plate and prevents it from moving inside the slightly oversized cavity or from contacting the inner surface of the cover glass. The cradle is made from two sheets of Mylar. One is cut to the width of the plate and folded at the top and bottom edges to form a Z-shaped spacer or spring; the other is cut to the height of the plate and is folded to form "Z" springs at the sides of the plate. The ends of the Mylar sheets should be trimmed to fit precisely into the spaces of the cover glass cavity. Once the cradle, the daguerreotype plate and the glass are precisely fitted into the matboard sink structure, the glass is sealed to the top surface of the matboard with paper tape. This system can be adapted to include an original brass mat behind the cover glass. The finished package can be easily over-matted and framed for display.

CasedobjectsGEH housing.JPG

Illustration: George Eastman House

Resealing Ambrotype packages
Reusing original tapes: This should be done when possible to preserve the original package components. It may be possible to change a deteriorated cover glass by releasing the tape from the front with minimal solvent application, removing the glass, fitting in the new glass and reactivating the original adhesive to secure the new glass. Damage on the original tape can be repaired using conventional methods. If original binding tapes must be removed and replaced with new materials, consider storing the removed tape fragments in the case tray, behind the package. Self-adhesive tapes: Many conservators prefer pressure-sensitive tapes for sealing cased photographs because they are easier to handle than paper tapes made with wet adhesives and they do not introduce moisture into the sealed package. Paper tapes such as Filmoplast P-90, Filmoplast P-91 or Filmoplast T (textile carrier) have been commonly used to reseal cased photographs. Polyester-backed or Mylar-backed tapes provide some moisture barrier. Notable among these are the 3M Polyester Film/Tape No. 850 (Silver), which is thin and flexible. It may be preferable to isolate the edge of the daguerreotype plate from contact with the adhesive. This can be done by laying a thin strip of nonadhering material down the centre of the sealing tape. Use 3-mil Mylar, Hollytex, Japanese paper or a thin strip of the sealing tape itself, turned so that its nonadhesive surface contacts the plate edge. See application instructions under "Plain paper tapes" below. Self-adhesive tapes can be used alone or be covered with the original paper sealing tape that has been removed and treated as described in Cased Photographs Treatment: Paper and Tapes and Mats entry.


  • 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



  • 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.
  • Barger, M. Susan. "Deterioration of Glass-supported Photographic Materials." New Directions in Paper Conservation: IPC Tenth Anniversary Conference. Oxford: The Institute of Paper Conservation, 1986, pp. D132-D133.
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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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