1. Collection ID Guide
2. Negatives

Negatives

The negative is a semi-transparent image on a transparent support. That support may be either glass or plastic film. A negative contains an inverse image (i.e. what is typically dark is light) of the photographed subject material. As film, still negatives can appear arranged on a film roll or as single image sheets. Silver gelatin film negatives will appear gray-black, while chromogenic color negatives comprise complementary colors or will have an overall red-orange mask. Glass negatives are commonly designated as black-and-white but are technically monochrome, meaning that they can possess a range of subtle tones within a single color. Negatives are generally the original source object from which positive copies and digital scans are derived at some later point. As a result, this makes them of high value for preservation efforts.

Glass Plate Negatives

• Albumen Glass Negative (1847 - 1860)
• Collodion Glass Negative (1851 - 1885)
• Gelatin Glass Negative (1878 - 1940)

Plastic Film Negatives

• Silver Gelatin Negative (B&W) (1889 - present)
• Chromogenic Color Negative (1939 - present)

Albumen Glass Negative

i

Synonyms

Dates

1847 – 1860

Image Tone

Ocher orange to olive green

Description

An albumen negative is comprised of an albumen and silver emulsion on a glass support. The image tone ranges from ocher-orange to olive green. Emulsion will appear creamy in dark areas. The image resolution is relatively sharp. Albumen negatives were typically made with thick, irregularly sized rough-cut glass. Corners may not be coated with emulsion.

Composition

Support	Binder	Image
Glass	Albumen	Silver

Deterioration

Minute star-shaped cracks in the emulsion, visible under magnification, are characteristic of albumen negatives. Significant cracking or fragmenting of the emulsion is indicative of a harmful environmental factor. The glass support is also vulnerable to breakage. Glass plate negatives may also exhibit signs of glass deterioration, including a whitish surface haze and/or an efflorescence of viscous droplets.

Risk Level

Moderate. Avoid touching or applying excessive pressure to the emulsion surface. Should be stored in a protective envelope and protected from excessive humidity.

Common Size(s)

Non-standard plate dimensions vary to extremes.

Background

Albumen negatives were produced from 1847 to 1860 and were used primarily by professional photographers. Due to a long exposure time (up to 15 minutes), the process was most frequently used to photograph landscapes and buildings. Although albumen negatives produce sharp images and do not require varnishing, they were superseded by collodion negatives because of the shorter exposure time.

Storage Environment

Cool storage (below 50 degrees) is recommended, though cold storage should be avoided for glass based images. Allowable Fluctuation: ±5°F; ±5% RH

Temp.	40–68°F (4–20°C)
RH	30–40% RH

Storage Enclosure(s)

Acid-free enclosures and/or folders strongly advised. Each negative should have its own enclosure to protect it from dust, handling damage, and changes in environmental conditions. Glass plates in good condition are best stored in a four-flap enclosure made from archival-quality paper; sleeves and envelopes are acceptable. Broken plates or delaminating negatives should be stored flat in a sink mount, also made from archival paper. Position photo emulsion side away from seams in paper enclosures. Such seams (if any) should be on the sides of the enclosure, not down its center. All storage materials should pass the Photographic Activity Test (PAT) as specified in ISO Standard 18916:2007.

Storage Orientation

Store vertically with dividers between each plate. May also be stored horizontally (flat), especially the larger or fragmented plates. Enclosures and folders may be stored in hanging files or archival storage boxes. Be mindful of full weight in boxes and on shelves. Wood cabinets should be avoided. Enameled steel, stainless steel, or anodized aluminum are preferred.

Collodion Glass Negative

i

i

i

i

i

i

Dates

1851 – 1885

Image Tone

Warm brown

Description

A collodion glass negative is comprised of a glass support with a collodion binder and silver image. When viewed in reflected light, the image tone ranges from warm light brown to dark brown. Thick glass plates were coated by hand, which resulted in an uneven thickness of the collodion that is particularly apparent at the corners.

Composition

Support	Binder	Image
Glass	Collodion	Silver

Deterioration

Collodion glass negatives are more sensitive to abrasion than albumen negatives and can be easily scratched. They are also vulnerable to breakage due to the glass support. Collodion glass negatives can develop networks of cracks along the edges of the plate, which may lead to image loss. Glass plate negatives may also exhibit signs of glass deterioration, including a whitish surface haze and/or an efflorescence of viscous droplets.

Risk Level

Moderate. Collodion is chemically unstable and very susceptible to abrasion, although they usually have a varnish or albumen coating that protects the surface. Do not attempt to clean the emulsion surface. Should always be protected from excessive humidity.

Common Size(s)

Non-standard plate dimensions vary to extremes.

Background

Collodion glass negatives were produced from 1851 to 1885 and were used primarily by professional photographers. The wet collodion process was sensitive enough for exposures to be done in only a few seconds; however, the plate had to be developed immediately while the collodion was still wet. Collodion "dry" plates were created to maintain the plate’s sensitivity over a longer time by adding hygroscopic material. This dry plate process was also known as the Taupenot process. The wet collodion process remained more common and was used by some photographers well into the 1880s, even after the emergence of the gelatin dry plate process.

Storage Environment

Cool storage (below 50 degrees) is recommended, though cold storage should be avoided for glass based images.Allowable Fluctuation: ±5°F; ±5% RH

Temp.	40–68°F (4–20°C)
RH	30–40% RH

Storage Enclosure(s)

Acid-free enclosures and/or folders strongly advised. Each negative should have its own enclosure to protect it from dust, handling damage, and changes in environmental conditions. Glass plates in good condition are best stored in a four-flap enclosure made from archival-quality paper; sleeves and envelopes are acceptable. Broken plates or delaminating negatives should be stored flat in a sink mount, also made from archival paper. Position photo emulsion side away from seams in paper enclosures. Such seams (if any) should be on the sides of the enclosure, not down its center. All storage materials should pass the Photographic Activity Test (PAT) as specified in ISO Standard 18916:2007.

Storage Orientation

Store vertically with dividers between each plate. May also be stored horizontally (flat), especially the larger or fragmented plates. Enclosures and folders may be stored in hanging files or archival storage boxes. Be mindful of full weight in boxes and on shelves. Wood cabinets should be avoided. Enameled steel, stainless steel, or anodized aluminum are preferred.

Gelatin Glass Negative

i

i

i

i

i

i

i

i

i

Synonyms

• Gelatin wet-plate (disambiguation)
• Gelatin dry-plate (disambiguation)

Dates

1878 – 1940

Image Tone

Gray-black; edge yellowing common

Description

A gelatin glass negative is comprised of a glass support with a gelatin binder and silver image. Image tones range from neutral gray to black. Unlike earlier glass plate negatives, gelatin plates were fully coated by emulsion and were cut to standard dimensions on factory-cut glass less than 2mm thick. A thin blank strip can be seen near the border. The gelatin and silver emulsion was applied by machine, resulting in a thin, smooth, even coating that also covered the edges.

Composition

Support	Binder	Image
Glass	Gelatin	Silver

Deterioration

Gelatin plates are often found in poor condition. As with other glass plates, cracks and breakage may occur. Delamination of the gelatin image-carrying layer is also common; it is usually caused either by poor preparation of the glass surface during manufacture or by exposure to extreme high and low relative humidity. Gelatin plates are also susceptible to oxidative deterioration, which appears as fading, yellowing, and silver mirroring. This is often caused by poor storage enclosures like old cardboard boxes.

Risk Level

Moderate. Delaminating emulsions can be protected under a plate of glass bound to the original support. Care should be taken to maintain constant relative humidity to prevent swelling of the gelatin emulsion, which will weaken its attachment to the glass support and cause delamination.

Common Size(s)

2½" × 2½" ; 2½" × 4" ; 4" × 5" ; 5" × 7" ; 8" × 10" ; 11" × 14" ; 14" × 17" ; 16" × 20" ; 18" × 22" ; 20" × 24"

Background

Gelatin glass negatives were used from 1878 to 1940 by professional and amateur photographers alike. Unlike collodion plates, gelatin plates were dry and retained their sensitized state for months. They could also be developed long after exposure, whereas collodion plates had to be developed immediately. These advantages allowed for the industrial manufacture and distribution of gelatin plates to a wider public, causing the photographic manufacturing industry to emerge and flourish beginning in the 1880s.

Storage Environment

Cool storage (below 50 degrees) is recommended, though cold storage should be avoided for glass based images.Allowable Fluctuation: ±5°F; ±5% RH

Temp.	40–68°F (4–20°C)
RH	30–40% RH

Storage Enclosure(s)

Acid-free enclosures and/or folders strongly advised. Each negative should have its own enclosure to protect it from dust, handling damage, and changes in environmental conditions. Glass plates in good condition are best stored in a four-flap enclosure made from archival-quality paper; sleeves and envelopes are acceptable. Broken plates or delaminating negatives should be stored flat in a sink mount, also made from archival paper. Position photo emulsion side away from seams in paper enclosures. Such seams (if any) should be on the sides of the enclosure, not down its center. All storage materials should pass the Photographic Activity Test (PAT) as specified in ISO Standard 18916:2007.

Storage Orientation

Store vertically with dividers between each plate. May also be stored horizontally (flat), especially the larger or fragmented plates. Enclosures and folders may be stored in hanging files or archival storage boxes. Be mindful of full weight in boxes and on shelves. Wood cabinets should be avoided. Enameled steel, stainless steel, or anodized aluminum are preferred.

Silver Gelatin Negative (B&W)

i

i

i

i

i

i

i

i

i

i

i

i

i

i

i

i

i

Dates

1889 – present; nitrate: 1889–1951; acetate: 1925–present; polyester: 1955–present

Image Tone

Gray-black

Description

A silver gelatin negative is a negative on a plastic film support made out of cellulose nitrate, cellulose acetate, or polyester. A gelatin and silver emulsion on the support's surface forms the image. Silver gelatin film is manufactured in standard camera formats and sold as either multiple-image rolls or single-image sheets. Nitrate film may be identified by "NITRATE" edge markings or manufacturer notch codes; similarly, acetate film may be identified by "SAFETY" edge markings or manufacturer notch nodes. Polyester film is not usually marked, but it may have "Estar" or "Cronar" edge markings.

Composition

Support	Binder	Image
Plastic (Nitrate, Acetate, or Polyester)	Gelatin	Silver

Deterioration

Nitrate: Cellulose nitrate film deterioration is exacerbated by either a humid or dry environment. In a humid environment, the emulsion may soften and become sticky. In a dry environment, the film becomes brittle. In the final stage of deterioration, nitrate film forms a solid mass that cannot be separated or handled safely. Nitrate film deterioration can be identified by the acrid, sharp odor as nitric and nitrous acids are released. These acidic vapors are damaging to surrounding objects, so deteriorating film must be evaluated to determine whether it should be discarded.

Acetate: Cellulose acetate film is susceptible to vinegar syndrome, causing the film base to shrink and the gelatin emulsion to pull up in folds. A strong vinegar odor is a telltale symptom in later stages of deterioration. Acetate deterioration is accelerated by humid conditions.

Polyester: Polyester film is inert, considered archival, and has a life-expectancy of 500+ years under proper storage conditions.

Risk Level

Nitrate: high; acetate: moderately high; polyester: low. The silver image on a black-and-white silver gelatin negative is relatively stable. However, the plastic supports are often unstable and prone to deterioration.

In the case of nitrate-based film, the preservation risk is very high. Acetate film is at a moderately high risk level and should be monitored closely for signs of deterioration. Polyester-based film is a low preservation risk.

Nitrate and acetate film negatives should be stored in dry, cool, well-ventilated areas. They are best stored in envelopes or pockets made of paper with an alkaline reserve.

Common Size(s)

35mm roll: 1.4" /35mm wide, 24 exposures (135 format)

Medium format roll: 2.35" /60mm wide, various exposure quantities (120 or 220 format)

Large format sheet: 4" × 5" ; 5" × 7" ; 8" × 10" ; as large as 20" × 24"

Background

Silver gelatin negatives were used from 1889 and continue to be used to the present day. Silver gelatin was the most widely used photographic negative of the twentieth century, and its significant presence in many archives and special collections reflects this. Before being produced for still photography, flexible film was intended for use in motion picture photography.

Cellulose nitrate sheet film was used from 1889 to 1951, when it was banned due to its flammable properties. Acetate safety film dates from 1925 to the present, although today it is only produced from cellulose triacetate. Polyester film dates from 1955 to the present. Of all three types of film-base, only polyester is regarded as a quality base for preservation purposes.

Storage Environment

Cool storage (below 50 degrees) is recommended, and colder is better for unstable plastic bases. Allowable Fluctuation: ±5°F; ±5% RH

Support	Temp./RH (Ideal range)
Nitrate	< 35°F (2°C); 20–30% RH
Acetate
	35°F (2°C) for 20–50% RH
	41°F (5°C) for 20–40% RH
	45°F (7°C) for 20–30% RH
Polyester	< 68°F (20°C); 20–50% RH

Storage Enclosure(s)

Acid-free enclosures and/or folders strongly advised. Due to cellulose nitrate and acetate’s inherent acidity, storage in a buffered, alkaline enclosure is recommended. Each negative should have its own enclosure to protect it from dust, handling damage, and changes in environmental conditions. This enclosure may be a paper (conservation-quality, acid-free) or plastic (uncoated polyester, polyethylene, polypropylene, cellulose triacetate) sleeve, envelope, or wrapper. Position photo image material away from seams in paper enclosures. Such seams (if any) should be on the sides of the enclosure, not down its center. All storage materials should pass the Photographic Activity Test (PAT) as specified in ISO Standard 18916:2007.

Storage Orientation

Store vertically with dividers between each negative. May also be stored horizontally (flat). Roll film is ideally segmented for more uniform, flat storage, but it may remain rolled. Enclosures and folders may be stored in hanging files or archival storage boxes. Wood cabinets should be avoided. Enameled steel, stainless steel, or anodized aluminum are preferred.

Chromogenic Color Negative

i

i

i

i

i

i

Synonyms

• Color negative
• Chromogenic process negative

Dates

1939 – present

Image Tone

Complementary full-color before 1947; red-orange tint (mask) after 1947

Description

Chromogenic process negative is a color image consisting of three superimposed gelatin image layers on top of a plastic film support (acetate or polyester). From top to bottom, the gelatin layers are infused with yellow, magenta, and cyan dye images; the dye molecules are then synthesized during processing. Film produced after 1947 has a red-orange tint (masking). Acetate film may be identified by "SAFETY" edge markings or manufacturer notch codes. Polyester film is not usually marked but may bear "Estar" or "Cronar" edge markings.

Composition

Support	Binder	Image
Plastic (Acetate or Polyester)	Gelatin	Yellow, magenta, and cyan dyes

Deterioration

Chromogenic negatives will fade, even in dark storage. Cold storage will slow the rate of deterioration. Much like chromogenic prints, negatives prior to the 1980s may discolor as a result of severe thermal fading of the cyan dye and poor storage in high temperatures. Unlike other processes, the progression of color negative stability is linear as coupler staining and dye stability have gradually improved over time. Deterioration of the film support varies depending on the type of plastic used.

Acetate: Cellulose acetate film is susceptible to vinegar syndrome, causing the film base to shrink and the gelatin emulsion to pull up in folds. A strong vinegar odor is a telltale symptom in later stages of deterioration. Acetate deterioration is accelerated by humid conditions.

Polyester: Polyester film is inert, considered archival, and has a life-expectancy of 500+ years under proper storage conditions.

Risk Level

Acetate: moderately high; polyester: moderately low. Chromogenic process negatives image material is especially sensitive to light and humidity, but it will gradually deteriorate even under good (dark, dry) storage conditions.

Acetate film is at a moderately high to high risk and should be monitored closely for signs of deterioration. Polyester film poses less of a risk, but it will still suffer from image fading. Cool and dry storage is advised; cold storage is ideal.

Common Size(s)

35mm roll: 35mm/1.4" wide, 24 exposures (135 format)

Roll cartridge: 16mm/0.6" wide film roll (110 format; after 1972)

Medium format roll: 2.35" /60mm wide, various exposure quantities (120 or 220 format)

Large format sheet: 4" × 5" ; 5" × 7" ; 8" × 10" ; as large as 20" × 24"

Background

Chromogenic process negatives date back to 1939, when Agfa debuted the chromogenic negative Agfacolor. Once Eastman Kodak followed with Kodacolor in 1942, color processes spread in the amateur photo market. They continue to be used up through the present day, but their use has receded considerably due to the proliferation of digital photography. Chromogenic components and dye stability have improved over time, most significantly after 1947 when a lack of color saturation was resolved by the addition of red-orange masking.

Storage Environment

Cool storage (below 50 degrees) is recommended, and colder is better for unstable plastic bases. Allowable Fluctuation: ±5°F; ±5% RH

Support	Temp./RH (Ideal range)
Acetate
	14°F (-10°C) for 20–50% RH
	27°F (-3°C) for 20–40% RH
Polyester
	14°F (-10°C) for 20–50% RH
	27°F (-3°C) for 20–40% RH
	36°F (2°C) for 20–30% RH

Storage Enclosure(s)

Acid-free enclosures and/or folders strongly advised. Due to the inherent acidity of cellulose acetate, storage in a buffered alkaline enclosure is recommended. Each negative should have its own enclosure to protect it from dust, handling damage, and changes in environmental conditions. This enclosure may be a paper (conservation-quality, acid-free) or plastic (uncoated polyester, polyethylene, polypropylene, cellulose triacetate) sleeve, envelope, or wrapper. Position photo image material away from seams in paper enclosures. Such seams (if any) should be on the sides of the enclosure, not down its center. All storage materials should pass the Photographic Activity Test (PAT) as specified in ISO Standard 18916:2007.

Storage Orientation

Store vertically with dividers between each negative. May also be stored horizontally (flat). Roll film may remain rolled or may be segmented for more uniform, flat storage. Enclosures and folders may be stored in hanging files or archival storage boxes. Wood cabinets should be avoided. Enameled steel, stainless steel, or anodized aluminum are preferred.

Resources

• ISO. (2007). 18916 Imaging materials: Processed imaging materials–Photographic activity test for enclosure materials. Geneva, Switzerland: International Organization for Standardization.
• Lavèdrine, B., Gandolfo, J., McElhone, J., & Monod, S. (2009). Photographs of the past: Process and preservation. Los Angeles, CA: The Getty Conservation Institute.
• For additional resources, see Photographic / Image Materials.