Daguerreotype. Courtesy of the Champaign County Archives, The Urbana Free Library.
Image
Silver-mercury
Identification
Mirror-like surface with dually positive/negative image depending on viewing angle. Typically housed in miniature hinged cases made of wood covered with leather, paper, cloth, or mother of pearl ornament.
Preservation
Should not be removed from original case.
Very sensitive to light, high humidity, atmospheric pollutants, and abrasion.
Metal plate may be tarnished (usually beginning at edges and moving toward center of image).
Cover glass may exhibit small white spots on inside surface.
Tintype (cased). Courtesy of the Champaign County Archives, The Urbana Free Library.
Image
Silver
Identification
Low contrast and limited tonal range. Image is created on an iron plate, most commonly carte-de-visite size (approx. 2 ½" × 4" to 4 ¼"). Tintypes were occasionally placed in hinged cases, in which case they are difficult to distinguish from ambrotypes. (A magnet can be used to conclusively identify the iron support.)
Preservation
Very sensitive to water and high humidity, which will cause oxidation and rusting of the iron support.
Exposure to intense light may cause image fading.
Iron support may become dented, bent, or scratched from mishandling and poor storage.
Low contrast with limited tonal range. Highlights appear milky-white. Image is created on a glass support backed with a dark opaque material like velvet; if this backing is not present, the image will appear negative. Typically housed in miniature hinged cases made of wood covered with leather, paper, cloth, or mother of pearl.
Preservation
Should not be removed from original case.
Very sensitive to light, high humidity, atmospheric pollutants, and abrasion.
Typically found as 16mm or 35mm unperforated roll film. Images may be positive or negative, depending on whether the item is a master or duplicate. Film base may be nitrate, acetate, or polyester – the type of support material greatly impacts preservation. Microfilm is used to create preservation and access copies of rare or deteriorating documents as well as of newspapers.
Preservation
Sensitive to high heat and humidity, yet should also not be stored in excessively dry conditions.
Acetate film may develop vinegar syndrome.
Nitrate film may deteriorate and become sticky or brittle; in the final stages of deterioration, it will become a solid mass.
Polyester film is stable and has a life expectancy of up to 500+ years if stored under proper conditions.
Standard microfiche is a flat film measuring 4" × 6". Microfiche commonly appears as a grid of micro images unreadable without the aid of a light reader. Images may be positive or negative, depending on whether the item is a master or duplicate. Film base may be acetate or polyester – the type of support material greatly impacts preservation.
Preservation
Sensitive to high heat and humidity, yet should also not be stored in excessively dry conditions.
Acetate film may develop vinegar syndrome.
Polyester film is stable and has a life expectancy of up to 500+ years if stored under proper conditions.
A photo-sensitized paper card measuring approximately 3" × 5" (sometimes 4" × 6") on which tiny printed matter is reproduced photographically in a greatly reduced form.
Preservation
Sensitive to light, humidity, and atmospheric pollutants.
Deterioration depends greatly on the quality of the paper.
Should be thought of as similar to a silver gelatin photo print.
Microprint (c. 1940 – unknown [no longer in production])
Microprint.
Image
Ink
Identification
An opaque 6" × 9" support paper with a mechanically printed ink image. Typically printed with 100 pages arranged in 10 rows and 10 columns.
Preservation
Sensitive to high humidity and moisture, and mechanical damage.
Deterioration depends greatly on the quality of the paper.
Should be thought of as similar to any ink-on-paper category.
Aperture card (backlit). Image by Wikimedia Commons user Ianare, available under a Creative Commons Attribution-ShareAlike license (CC-BY-SA-2.5).
Image
Silver
Identification
A microfilm cell mounted in a thick paper or cardboard punch card. The card is punched with machine-readable metadata associated with the image; this information may also be printed or typed on the card. The content of the film is usually a reference document or image, such as an engineering drawing, map, or another large single-page document.
Preservation
Sensitive to high heat and humidity, yet should also not be stored in excessively dry conditions.
Acetate film may develop vinegar syndrome.
Nitrate film may deteriorate and become sticky or brittle; in the final stages of deterioration, it will become a solid mass.
Polyester film is stable and has a life expectancy of up to 500+ years if stored under proper conditions.
Albumen glass negative. Attributed to Claude-Marie Ferrier, 1851 (RP-F-F15048). Image courtesy of Rijksmuseum Amsterdam, available in the public domain.
Image
Silver
Identification
Negative image on glass. Image tone ranges from ocher orange to olive green. Emulsion may be uneven as a result of hand-coating.
Preservation
Glass support is fragile and may develop cracks; otherwise this format is relatively stable.
Should not be exposed to excessively high or low humidity.
May exhibit signs of glass deterioration, including a whitish surface haze and/or an efflorescence of viscous droplets.
Collodion glass negative (backlit). Image by Flickr user James Morley, available under a Creative Commons Attribution NonCommercial license (CC BY-NC 2.0).
Image
Silver
Identification
Negative image on glass. Image tone is warm brown. Emulsion may be uneven as a result of hand-coating.
Preservation
Emulsion is very sensitive to abrasion.
Glass support is fragile and may develop cracks.
Should not be exposed to excessively high or low humidity.
May exhibit signs of glass deterioration, including a whitish surface haze and/or an efflorescence of viscous droplets.
Gelatin glass negative (alongside silver gelatin print). Image courtesy of Image Permanence Institute, Graphics Atlas.
Image
Silver
Identification
Negative image on glass. Image tone ranges from neutral gray to black. Emulsion was applied by machine; it is therefore smooth, even including coverage along the edges.
Preservation
Often found in poor condition.
May exhibit signs of oxidation including yellowing, fading, and silver mirroring.
Delamination of the image-carrying layer is common.
Silver gelatin negative. This large format negative is on a nitrate base film.
Image
Silver
Identification
Negative image on plastic support. Film base may be nitrate, acetate, or polyester — the type of support material greatly impacts preservation. May be found as multiple-image rolls or single sheets in standard camera formats.
Preservation
Sensitive to high heat and humidity, yet should also not be stored in excessively dry conditions.
Acetate film may develop vinegar syndrome.
Nitrate film may deteriorate and become sticky or brittle; in the final stages of deterioration, it will become a solid mass.
Polyester film is stable and has a life expectancy of up to 500+ years if stored under proper conditions.
Chromogenic negative. Image by Flickr user Great Beyond, available under a Creative Commons Attribution NonCommercial ShareAlike license (CC BY-NC-SA 2.0).
Image
Colored dyes
Identification
Negative color image on plastic support. Film base may be acetate or polyester — the type of support material greatly impacts preservation. Film produced after 1947 has a red-orange tint.
Preservation
Very sensitive to light and heat, which cause accelerated image fading.
Fading will occur even in dark storage. Rate of deterioration will be slowed, however, if kept in cold dark storage.
Acetate film may develop vinegar syndrome.
Polyester film is stable and has a life expectancy of up to 500+ years if stored under proper conditions.
Woodburytype. Image courtesy of Image Permanence Institute, Graphics Atlas
Image
Carbon pigment
Identification
No discernable image pattern when viewed under magnification; appears almost identical to a carbon print. Monochrome image—typically purplish-brown, brown, or black—with continuous rich tones. Exhibits slightly more of an image-relief effect than carbon prints: shadow areas of image are glossier and more elevated than highlight areas (differential gloss).
Preservation
Darker image areas may develop cracks.
Unmounted prints will tend to curl in on themselves.
Deterioration is largely dependent on the quality of paper support rather than the ink.
May be identified by image pattern (as seen under low magnification): fine "worm-like" reticulation pattern. Images may be printed in color or, more commonly, monochrome. Ink in the shadows is glossier than that of a photogravure. Collotype postcards may have "Albertype" printed on verso.
Preservation
Deterioration is largely dependent on the quality of paper support rather than the ink.
Gravure (late 1870s – present; decline after 1920)
Photogravure.
Image
Ink
Identification
May be identified by image pattern (as seen under low magnification): irregular pattern (aquatint grain) or a regular screen pattern comprised of equally-sized square cells. Images may be printed in monochrome or color. Monochrome images are more common, usually brown, dark green, or black.
Preservation
Deterioration is largely dependent on the quality of paper support rather than the ink.
Offset lithograph. Courtesy of the Champaign County Archives, Urbana Free Library.
Image
Ink
Identification
May be identified by image pattern (as seen under low magnification): fine, soft-edged regular rosette dot pattern. Images may be printed in monochrome or color. Different colored layers may be misaligned; they are best seen in areas of detail and along edges of image.
Preservation
Deterioration is largely dependent on the quality of paper.
May be identified by image pattern (as seen under low magnification): hard-edged grid,"waffled," mosaic-like. Images may be printed in monochrome or color. Poor reproduction of detail.
Preservation
Deterioration is largely dependent on the quality of paper support rather than the ink.
Salt print. Image courtesy of the Chicago History Museum: Graceland Cemetery Photo Scrapbook - X.2084.2002 PPL.
Image
Silver
Identification
Untoned images range from light brown to reddish brown. Toned images are purplish-brown. Faded images may appear yellowish-brown. Paper fibers are clearly visible under low magnification. Surface sheen is matte with a rough texture.
Preservation
Sensitive to pollutants, humidity, and light.
Images are often faded with pale yellow discoloration along edges.
Untoned images are particularly vulnerable to fading.
Foxing, staining, and embrittlement of the support paper are common.
Albumen print. Image courtesy of the University of Illinois Board of Trustees.
Identification
Image tone ranges from purplish brown to chocolate brown. Faded images will appear light yellow brown. Prints are made on smooth thin paper that is then mounted to a card. Surface sheen ranges from semi-glossy to glossy. Paper fibers are clearly visible under low magnification.
Preservation
Likely yellowed and faded; distinct yellow or yellowish brown staining in highlight and non-image areas.
Cracked or crazed pattern may be seen in dark areas of image.
Foxing is common.
Unmounted prints will curl up very tightly.
Carbon Print (1855 – 1950s; popular from 1870 – 1910)
Carbon print. Image courtesy of Image Permanence Institute, Graphics Atlas.
Image
Carbon pigment
Identification
Characterized by dense, dark image tones, usually either neutral black, reddish brown, or chocolate brown. Surface exhibits differential sheen, with dark areas of the image appearing more glossy than semi-matte highlights. Paper fibers are visible in highlights under low magnification. Print may be labelled "Permanent" or "Autotype." Images exhibit little to no fading or yellowing. Monochrome equivalent/predecessor of the color carbro process.
Preservation
Dark image areas may develop cracks.
Tendency to curl when unmounted.
Deterioration is largely dependant on the quality of paper support used.
May be identified by subtle iridescent effect on print’s surface when viewed under fluorescent light. Image tones range from reddish-brown to purple. Paper fibers are not visible. Surface sheen ranges from semi-glossy to glossy, which should set it apart from the matte collodion POP. Very little image fading.
Preservation
Extremely sensitive to surface abrasion, which will result in white scratches where the image layer has been removed.
May delaminate or develop tiny cracks in emulsion as a result of fluctuating relative humidity.
Cyanotype. Note the vibrant Prussian blue color and visible paper fibers. Image courtesy of the Chicago History Museum.
Image
Prussian blue pigment
Identification
Easily identified by brilliant Prussian blue image with continuous tone. Poor contrast and sharpness. Paper fibers are clearly visible under low magnification. Surface sheen is matte with rough texture.
Preservation
Very sensitive to light.
Deterioration is largely dependant on the quality of paper support used.
Platinum print. Image courtesy of Image Permanence Institute, Graphics Atlas.
Image
Platinum or palladium
Identification
Image tone varies based on toning; may be neutral, warm brown, brown-black, or purple/blue-black. Paper fibers are clearly visible under low magnification. Surface sheen is matte. Rich, soft image tone with no fading or silvering.
Preservation
Deterioration is dependant on the quality of paper support used.
If stored in contact with another piece of paper, there may be signs of catalytic degradation in the form of a mirror image "burned" into the facing paper.
Image tone varies. Untoned images are neutral gray-black. Toned images may be brown, sepia, yellowish, or purplish. Surface sheen may be matte, glossy, or textured. Paper fibers are not visible, except in rare cases of very early pre-1900 prints. Postcard prints will have a continuous image tone, differentiating them from photomechanically produced postcards.
Preservation
Sensitive to atmospheric pollutants, heat, and high humidity.
Often exhibit silver mirroring, especially along edges and in dark image areas.
Image fading and yellow-brown discoloration beginning in highlights and spreading to rest of image.
Resin-coated silver gelatin prints may develop redox blemishes.
Gelatin POP print (toned). Photo courtesy of Champaign County Archives.
Image
Silver
Identification
Image tone varies from red-brown to purple-brown for toned images and light yellow-brown to yellow-green for faded images. Surface sheen may be matte or glossy. Paper fibers are not visible. Difficult to distinguish from collodion print.
Preservation
Very sensitive to high and low humidity, which will cause emulsion to crack or become soft and sticky.
Matte collodion POP print. Photo courtesy of the Champaign County Archives.
Image
Silver
Identification
Image tone varies; most commonly brownish black, purplish black, or neutral black. Surface sheen is semi-matte with slight luster. Little to no image fading. May appear similar to a platinum print.
Preservation
Extremely sensitive to surface abrasion, which will result in white scratches where the image layer has been removed.
May delaminate or develop tiny cracks in emulsion as a result of fluctuating relative humidity.
Color carbro print. Image courtesy of Image Permanence Institute, Graphics Atlas.
Image
Pigmented gelatin
Identification
Full-color print. Surface exhibits differential sheen, with dark areas of the image appearing more glossy than semi-matte highlights. Pigment particles can be seen under low magnification. Color layers may appear misaligned or separated, visible particularly along borders and in areas of detail. Vivid colors with good image permanence and little to no fading. Tri-color equivalent of the Carbon Print.
Preservation
Sensitive to abrasions and low relative humidity, which may cause the gelatin layers to crack and delaminate.
Dye-transfer print. Image courtesy of Image Permanence Institute, Graphics Atlas.
Image
Color dyes
Identification
Full-color print. May be identified by misalignment of the color dye layers, particularly visible along image edges. Print surface is smooth and may be semi-matte or glossy. When viewed under UV light, the magenta dye fluoresces orange. Dye-transfer prints were usually produced by fine artists or high-end photo studios.
Preservation
Sensitive to light and water.
Stable; will retain excellent image stability if kept in proper storage.
Full-color print. May be identified by manufacturer’s backprint or back stamp, which often contains information about processing, date, and materials used. Fiber-based prints have white borders around the edges; resin-coated prints do not.
Preservation
Extremely sensitive to light and humidity.
Yellow staining is common, most apparent in highlights and borders.
Prints created before 1980 may have reddish discoloration.
Silver dye-bleach print. Image courtesy of Image Permanence Institute, Graphics Atlas.
Image
Silver and azo dyes
Identification
Full-color print on polyester, acetate, or resin-coated paper. Image is vivid with high contrast and has little to no fading. Surface sheen is either semi-gloss ("pearl") or high-gloss with a metallic-like finish. There may be a black margin around the image. Resin-coated papers will likely have a manufacturer’s backprint.
Preservation
Prolonged exposure to light and airborne pollutants may cause color shift.
Sensitive to water, pollutants, abrasion, and fingerprints.
Polyester supports are relatively stable.
Acetate supports will yellow and may develop vinegar syndrome.
Resin-coated supports may curl, become embrittled, and crack.
Instant Photos
Instant Photo, B&W (1947 – 2008; limited production continues to present)
B&W instant photo (peel-apart). Photo courtesy of the Champaign County Archives.
Image
Silver
Identification
Monochrome image with glossy surface sheen. White borders may have residue from peel-apart layer. May have one border unproportionately larger than the other three, where processing chemicals were squeezed out when the photo was removed from the camera. Polaroid prints produced after 1968 will feature a manufacturer’s stamp on verso.
Preservation
Fading and discoloration is common, especially in early coated prints.
White border around image should never be cut or removed.
Full color image with very glossy surface sheen. White borders may have residue from peel-apart layer. May have one border unproportionately larger than the other three, where processing chemicals were squeezed out when the photo was removed from the camera. Polaroid prints produced after 1968 will feature a manufacturer’s stamp on verso.
Preservation
Fading and discoloration common.
White border around image should never be cut or removed.
Very sensitive to light and atmospheric pollutants.
B&W glass slide. Courtesy of Landscape Architecture, UIUC, University of Illinois Board of Trustees.
Image
Silver
Identification
Monochrome (gray-black) image on glass. Image tone varies, typically gray-black, warm brown, ocher orange, or olive green. Slides were sometimes hand-colored or tinted. Lantern slides have a cover glass and are sealed along the edges with black tape. Stereograph slides are rectangular and feature two nearly identical images side-by-side.
Preservation
Glass support is fragile.
Sensitive to atmospheric pollutants and light.
Gelatin slides are prone to delamination and flaking of image layer.
Black-and-white film slide. Courtesy of Landscape Architecture, UIUC, University of Illinois Board of Trustees.
Image
Silver
Identification
Monochrome positive transparent image on plastic support. Plastic support may be nitrate, acetate, or polyester — the type of support material greatly impacts preservation. Individual slides are placed in plastic, cardboard, or metal mounts for use in projectors. Relatively rare.
Preservation
Sensitive to high heat and humidity, yet should also not be stored in excessively dry conditions.
Acetate film may develop vinegar syndrome.
Nitrate film may deteriorate and become sticky or brittle; in the final stages of deterioration, it will become a solid mass.
Polyester film is stable and has a life expectancy of up to 500+ years if stored under proper conditions.
Color film slides (with mounts). Courtesy of Landscape Architecture, UIUC, University of Illinois Board of Trustees.
Image
Color dyes
Identification
Full-color positive transparent image on plastic support. Plastic support may be acetate or polyester — the type of support material greatly impacts preservation. Individual slides are placed in plastic, cardboard, or metal mounts for use in projectors.
Preservation
Very sensitive to light and heat; will fade even in dark storage.
Acetate film may develop vinegar syndrome.
Polyester film is stable and has a life expectancy of up to 500+ years if stored under proper conditions.
Inkjet print. Courtesy of the Champaign County Archives, The Urbana Free Library.
Image
Monochrome or color; dye- or pigment-based ink
Identification
Produced on a variety of papers using either pigment- or dye-based inks. May be identified by droplet pattern seen under magnification, appearing as a super-fine random dot structure.
Preservation
Deterioration depends greatly on the quality of the paper and type of ink.
Sensitive to light, high humidity, and atmospheric pollutants.
Appears similar to electrostatic copies, but image will appear cleaner and heavier.
Preservation
Deterioration depends greatly on the quality of the paper.
Color prints are particularly sensitive to moisture and light.
Resources
Lavèdrine, B., Gandolfo, J., McElhone, J., & Monod, S. (2009). Photographs of the past: Process and preservation. Los Angeles, CA: The Getty Conservation Institute.
