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Chromogenic negatives

Risks of Handling/Use

Generally, handling and use heightens the risk of damage to your materials, be it through neglectful handling (e.g. touching photo emulsion with bare hands) or irresponsible operation of access equipment. This is a risk posed by patrons and staff alike, intentional or not.

Handling and Collections Care

One of the easiest areas to implement protections for collections is through careful handling and sensible collections care. The unfettered use and handling of materials heightens the general risk of damage--be it through neglectful handling (e.g. touching photo emulsion with bare hands) or irresponsible operation of access equipment. Whether intentional or not, this is a risk posed by patrons and staff alike.

Examples of neglect, mishandling, and mismanagement include:

• Pressure-sensitive (such as "Scotch®" brand) tape to mend tears.
• Permanent or volatile inks used to label documents (even the back side).
• Folding materials to fit into a given box or enclosure.
• Poor handling: Not washing and drying hands before handling fragile documents; or not using gloves when handling materials that could be damaged by contact with oils on the skin (for example: gloves must always be worn when handling metals).
• Inadequate storage or exhibit environments, such as areas with excessive climate swings or the use of poor display mounts.
• Inadequate packaging/padding for shipping
• Lack of bibliographic control over holdings, which has led to the harmful and excessive use of unique or vulnerable items.

General Recommendations:

• Use archival-quality folders, boxes, sleeves, and other enclosures to support and house materials of differing shapes and sizes. Avoid use of acidic containers such as brown paper bags and shipping or moving boxes.
• Use only Photographic Activity Test (PAT)-compliant storage enclosure materials for valuable photographic materials.
• Wear gloves (either cotton or nitrile) while handling archival photographic emulsion materials and museum objects.
• Avoid wearing cotton gloves while handling particularly fragile or slippery items, since gloves can hamper tactile senses and lead to accidentally dropping and breaking objects.
• Handle fragile materials as little as possible.
• Use clean, dry hands with carefully trimmed nails to handle materials (even when wearing gloves).
• Use both hands and ask for assistance when handling/moving oversized materials.
• Remove jewelry and accessories, including anything hanging around the neck or clothes that may inadvertently come into contact with and damage materials, such as: necklaces, headphones, glasses hanging around the neck, nametags, scarves, rings, watches, bracelets, ties, loose sleeves, and belts. Avoid wearing loose clothing.
• During transport, use enclosures, supports, book carts, and other equipment as appropriate to minimize the risk to materials. Use materials like foam and snake supports to ensure that items are supported and do not come in contact with other items or with the sides of carts during transport. Always ensure sufficient assistance while transporting items.
• Only use pencils for direct labeling (e.g. on a photo verso) of paper, AV, and photographic materials or folders/enclosures. Never use or carry pens around items and materials.
• Ensure that patrons know and understand guidelines on proper handling of all fragile materials.
• Ensure that staff, volunteers, and patrons are adequately trained in handling collection materials.

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Additional Copies

The use of additional copies for reference or display purposes is highly recommended, particularly if the item is an original or valuable. This provides broader access to the content while also protecting the original document from user wear and tear or environmental factors.

Recommendations for care of original object:

• Ideally, originals should be used once to produce an access copy, facsimile, or surrogate;
• Copies would then be put to use by the institution in place of the original, sustaining the wear and tear of patron use or prolonged exhibition.

To learn more about best practices for use and access, including resources for creating digital surrogates, see Use & Access in the User-Manual.

Orientation in Storage

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.

Storage Container

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.

Wood cabinets should be avoided. Enameled steel, stainless steel, or anodized aluminum are preferred. All storage materials should pass the Photographic Activity Test (PAT) as specified in ISO Standard 18916:2007. Cool and dry storage is advised—cold storage is ideal.

Labeling

If your item has any kind of labeling on the container, the item itself, or any related material, we highly recommend that you return to the Basic Info section and enter this information in the appropriate field(s).

Labeling on a container or item, if it is correct, can offer important clues about what is on the negative, and/or help to identify the base. Acetate film may be identified by "SAFETY" edge marking or manufacturer notch codes. Polyester film is not usually marked, but it may bear "Estar" or "Cronar" edge markings.

Physical Damage

Damage can range from scratches in the emulsion layer to torn film, although film with a polyester base does not tear easily. Film-based photogrpahic materials can be very fragile if there are tears, perforations, or other forms of severe mechanical damage.

Physical Damage: Film Decay

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.

Mold / Pest Damage

Mold

The gelatin binder of a photographic emulsion is an especially good nutrient for mold. If your item is exhibiting white or brown patches or if you see a lattice-like growth along the edges, you are most likely viewing mold. Negatives stored in hot, humid environments (generally above 65% relative humidity) is most vulnerable to mold, mildew, and fungus contamination. Mold will typically damage the edges of photographic material first. If mold has eaten into the emulsion, the item will be noticeably and irreparably damaged, exhibiting feathery-like distortions or dull spots on the projected image. Mold can be removed through cleaning and then storing the items in a cold, dry environment, but this should be done responsibly.

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Pests

Pests like insects and rodents tend to like paper and textile materials more than plastic-based materials. That said, pests can still do damage. Insects can be attracted to the organic components of emulsion (i.e. gelatin). Film cans, both plastic and metal, tend to keep most pests out. When assessing the exposure of your collections to pests, it is necessary to look not just at the materials themselves and their containers, but also at the larger environment. Insects and rodents tend to leave droppings in areas they inhabit. Insects tend to leave behind a substance called frass, which is the undigested fibers from paper. If you see droppings and/or frass in the storage area, it is a strong sign that your materials are being exposed to pests. Small, irregular holes on paper-based enclosures are also a sign that pests have attacked your materials.

Some tips for reducing your materials' exposure to pests are to refrain from eating anywhere near your collections materials. Crumbs and food waste draw pests, so eat far from your collections. Another tip applying to both pests and mold is to be cautious about donated materials when you receive them. Pests and mold can hitch a ride into your facility on these materials, so having a good, clean staging area where you can inspect donated items for, among other things, pest and mold evidence can help you reduce your storage environments' exposure to both.

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Film Base Decay

Chromogenic color negatives are exclusively acetate or polyester. Acetate film may be identified by "SAFETY" edge marking or manufacturer notch codes. Polyester film is not usually marked, but it may bear "Estar" or "Cronar" edge markings. If you are having difficulty identifying your microfilm base, jump to the Film Base Materials in the Collection ID Guide.

Deterioration of the film support varies depending on the type of plastic.

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.

Acetate

One of the key signs that an acetate film is degrading is the presence of a vinegar smell. This degradation results from the chemical breakdown of the acetate into acetic acid and is known as "vinegar syndrome." When the film can is opened, the odor can be very strong and unmistakable.

Although the vinegar odor is often the most obvious sign that an acetate film is degrading, it is not the only sign. Acetate film that is degrading becomes brittle. The film loses its suppleness and does not gently curve around the core or reel; instead, the film appears jagged or "spoked." The film base will also shrink. To help prevent or slow acetate decay, you can place molecular sieves in your film cans. These desiccants will help absorb acetic acid and moisture in a sealed film can.

The PSAP has also adapted the Image Permanence Institute's A-D Strip scoring method to rate vinegar syndrome in acetate film. These strips, developed by the Image Permanence Institute, change color based upon the level of acidic vapor detected. A-D strips are an excellent way to score and monitor vinegar syndrome; they can give you a finer level of assessment beyond visual and olfactory cues. Using A-D Strips in conjunction with the PSAP can make your vinegar syndrome assessment much more accurate. For more information about A-D Strips, click here: https://www.imagepermanenceinstitute.org/imaging/ad-strips.

The following is a guide to rating acetate decay (vinegar syndrome):

No Deterioration. This film is suffering from no acetate decay.

Deterioration Starting. Acetate decay is starting. This film should be moved to cold storage if possible and monitored. The film is flexible, with little (less than 1%) to no apparent shrinkage. There may be a very faint vinegar smell.

Actively Deteriorating. This film is actively deteriorating. It should be moved to cold storage if possible and duplicated. The film will have a stronger vinegar odor and may exhibit shrinkage (between .8 to 2%). The film may be able to be accessed/read in-house by an experienced technician using maintained and functioning equipment. The film will also exhibit some waviness along the edges; it may curl slightly and resist lying flat.

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Critical Deterioration. This film is exhibiting shrinkage and warping. It may be difficult or impossible to handle the film without damaging it. The film should be frozen if possible. The vinegar odor is unmistakable. (You should exercise caution when opening all film cans and avoid sticking your nose into the can—you could be in for a very unpleasant and potentially dangerous surprise!) The emulsion layer looks cracked and may already have separated from the film base. The film is very brittle and inflexible. It may appear to be "spoking" in the film can: the film pack does not look rounded but appears more angled. White powder may be visible on the edges of the film. In this stage of decay, the content may be unrecoverable. Acetate-based film in critical condition often cannot safely be read or played back in-house—if it can be at all. However, depending upon the flexibility of the film, the condition of the emulsion and image area, and shrinkage, a highly qualified vendor may be able to recover the content.

In order to slow or stop acetate decay, it should be stored in cold to frozen conditions (32–40°F and less than 32°F, respectively). Once the decay starts, it cannot be reversed. If a film is discovered to be acidic and succumbing to vinegar syndrome, it should be separated from other "healthy" films as it can "infect" the other films.

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Image Tint

Chromogenic process negative is a color image consisting of three gelatin image layers, one on top of the other, atop a plastic film support made of either acetate or polyester. The gelatin layers are infused from top to bottom with yellow, magenta, and cyan dye images. During processing, the dye molecules are synthesized. Film produced after 1947 has a red-orange tint (masking).

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Fading

Chromogenic negatives will fade, even in dark storage, although cold storage will slow the rate of deterioration. Unlike other processes, the progression of color negative stability is linear: that is, coupler staining and dye stability have gradually improved over time.

Much like chromogenic prints, negatives prior to the 1980s may have reddish image discoloration as a result of the unstable cyan dye’s severe thermal fading and poor storage in high temperatures. Chromogenic color negatives are extremely sensitive to light and humidity, and they will exhibit some dye fading even if kept in dark, cold storage.