Negative Notes
Modified: February 14, 2026 7:58 PM Created: September 17, 2025 3:27 PM Master Type: Notes Hide: No Starred: No Status: Unassigned
This is especially true for the vast majority of paper and cellulose based items. Because of its ability to neutralise acids and extend the life of paper, photographs, textiles, and artefacts, buffering is more often than not a benefit in interleaving tissue, storage boxes, folders, envelopes and other paper enclosures. For most photographic materials, including black and white prints, colour prints, and albumen prints, either buffered or unbuffered enclosures are satisfactory – the PAT test is a separate test which evaluates a storage material’s properties when storing photographic materials.
https://www.preservationequipment.com/Blog/Blog-Posts/Buffered-or-unbuffered-storage
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When you are looking for a storage material that is appropriate for use with your photographs check that it conforms to ISO 18902 (Imaging materials – Processed imaging materials – Albums, framing and storage materials) and that it has passed the Photographic Activity Test [PAT] (ISO 18916 – Imaging materials – Processed imaging materials – Photographic Activity Test for enclosure materials). https://www.preservationequipment.com/Blog/Blog-Posts/Photograph-storage-materials-What-should-you-use///
Negatives Poster Booklet Nitrate Edge printing Films produced between the 1930s and the 1950s were often edge printed with the word “NITRATE” to differentiate the film support from the new acetate film. After 1930, safety film made of cellulose acetate started being used and needed to be distinguished from its highly flammable predecessor. Therefore, the word “SAFETY” was edge printed on these films. However, edge printing was not done by all manufac- turers, nor was it done on all roll film formats. Curling Early cellulose nitrate amateur roll films were not edge marked, but can be identified by their tendency to curl into very tight scrolls. Later, the nitrate support was coated with gelatin on the reverse side to prevent such curling. These gelatin anti-curl layers started being used in 1903. Notch codes Nitrate sheet films may have different notch codes on the upper right edge (emulsion facing up), which were made for the purpose of identifying the film type or emulsion side in the dark. A “V” notch code (first from the edge) can identify Kodak sheet film prior to 1949 as nitrate. Film pack negatives do not have notch codes.61
Acetate Edge printing Cellulose acetate is usually edge printed with the word SAFETY. Depending on the place of manufacture, the symbol “°” may be added between the letters (e.g., “S°AFETY” for film manufactured by Kodak in the United States). Notch codes Film notch codes are cuts on the edge of the sheet films that can be used to identify the film type and locate the emulsion side in the dark. Cellulose acetate films produced by Kodak between 1925 and 1949 carried a U-shaped notch (first from the edge).77 NDCC
- Edge printing Many manufacturers stamped professional sheet films with an identification along one border. The words generally identified the manufacturer and the type of film: nitrate or safety. Unfortunately, not all manufacturers adopted edge printing identification. It wasn’t done on either early nitrate negatives or on some roll film formats. Amateur roll films were not marked but can be identified by their tendency to curl into very tight scrolls (later roll films were coated on both sides to prevent such curling). Notch codes can also identify sheet film as nitrate. A “V” notch code (first from the edge) will identify pre-1949 Kodak sheet film as nitrate while a “U” shaped notch (first from the edge) will indicate the Kodak film is acetate. Note that a nitrate negative may have been copied at some point and the edge printing from the original will appear on the copy. Therefore, just because you see the word “nitrate” does not guarantee that it is. See the section on testing to be sure.
- Edge printing Many manufacturers stamped professional sheet films with an identification along one border. The words generally identified the manufacturer and the type of film: nitrate or safety. Unfortunately, not all manufacturers adopted edge printing identification. It wasn’t done on either early nitrate negatives or on some roll film formats. Amateur roll films were not marked but can be identified by their tendency to curl into very tight scrolls (later roll films were coated on both sides to prevent such curling). Notch codes can also identify sheet film as nitrate. A “V” notch code (first from the edge) will identify pre-1949 Kodak sheet film as nitrate while a “U” shaped notch (first from the edge) will indicate the Kodak film is acetate. Note that a nitrate negative may have been copied at some point and the edge printing from the original will appear on the copy. Therefore, just because you see the word “nitrate” does not guarantee that it is. See the section on testing to be sure.
A third method of film base identification is based on the observations of deterioration characteristics. Nitric oxide, nitrous oxide, and nitrous dioxide are all released as gases from the decomposition of cellulose nitrate. In the presence of atmospheric moisture, these gases combine with water to form nitric acid. The formation of nitric acid acts to further degrade cellulose nitrate film, and it can destroy enclosures in which the negatives are stored. It can even damage materials stored in close proximity to the collection. Because of their extreme flammability, institutions should isolate and properly store cellulose nitrate materials—especially when those materials are in a deteriorated condition. They should be stored in a controlled environment of relatively low humidity, or ideally, in cold storage. Cellulose nitrate decomposition can be very rapid. Deterioration is generally categorized in six progressive stages: Level 2 The negatives begin to yellow and mirror. Level 3 The film becomes sticky and emits a strong
noxious odor (nitric acid). Level 4 The film becomes an amber color and the image begins to fade. Level 5 The film is soft and can weld to adjacent negatives, enclosures and photographs. Level 6 The film degenerates into a brownish acid powder. 3 • NEDCC • Leaflet 5.1: A Short Guide to Film Base Photographic Materials: Identification, Care, and Duplication • www.nedcc.org Most negatives will retain legible photographic detail into the third stage of decomposition. These negatives may become brittle, but—with careful handling—they can be duplicated. Negatives in the fourth, fifth, and sixth stages of decomposition generally have decreasing areas of legible image and should be either placed in cold storage or digitized before the image completely fades away
Oxford Publications The original nitrate negatives are usually one of these sizes: 35mm or 2 1/4 inch roll film, or 3x4” or 4x5” sheet film. Some 5x7” and 8x10” sheet films were also used. How to Identify Nitrate Film Decay •Labels: Check to see if the word ‘Nitrate’ is embossed or printed on the edge of the film. Some nitrate films have been copied onto less-flammable safety film, which might have the words ‘Nitrate’ and ‘Safety’ printed on the film. • •Deterioration: If film is in any of the Levels of decay we noted above, assume it’s nitrate. But if the film is wrinkled or smells like vinegar, it’s most likely safety film. • •Dates: ◦Assume that any film dated before 1920 is nitrate film. ◦ ◦Look for notches on the edge of any Kodak film dated from 1921 to 1940. Hold the film with the notches in the upper right corner. If the first notch from the right is shaped like a ‘V,’ you’re holding nitrate film. If the first notch looks like a ‘U,’ it’s most likely safety film.
◦ ◦For non-Kodak film from 1921 to 1940, all film from 1940 to 1950, and any film that can’t be dated – look for the signs of deterioration we mentioned above.