Storing slides and film negatives

Film comes in three common bases. Polyester is stable. Cellulose nitrate and cellulose acetate, the "safety film" that replaced it, are not, and once they start to break down the damage can't be reversed. Nitrate gives off toxic fumes and becomes more dangerous as it deteriorates. Acetate gives off acetic acid, the vinegar syndrome, which damages film and papers stored near it. Knowing what you have comes first.

What you need

• Lint-free gloves, since oils and sweat damage the image
• Enclosures that passed the Photographic Activity Test (PAT)
• An archival box

Steps

1. 1

   Put on gloves

   Hold negatives and slides by their edges, and never with bare hands.

   2 min

2. 2

   Read the edge markings

   Look along the film's border for printed words. "Nitrate" means cellulose nitrate, "Safety" means acetate, and "Estar" or "Cronar" means polyester. A copy negative can carry both "nitrate" and "safety", meaning an acetate copy of nitrate film. Some film has no marking at all.

   20 min

3. 3

   Check for notches and damage

   On Kodak film from before 1949, a V-shaped notch nearest the edge marks nitrate and a U-shaped one marks acetate. A sharp acid smell, stickiness or an amber tint points to nitrate breaking down. A vinegar smell, curling, shrinking or brittleness points to acetate.

   10 min

4. 4

   Choose the enclosures

   Use sleeves or envelopes that passed the PAT and meet the ANSI IT9.2 standard. Where test results aren't available, pick lignin-free, 100% rag paper that isn't strongly colored, especially not black. Skip glassine, and never use PVC, often sold as vinyl.

   5 min

5. 5

   Rehouse the film

   Slide each strip or slide into its own enclosure. In a paper envelope with a seam, face the image side away from the seam. Use paper rather than plastic for nitrate and early safety film, since plastic traps the gases they give off.

   30 min

6. 6

   Label and box it

   Note what's in each paper enclosure on its outside, since paper takes writing easily. Stand them in an archival box somewhere cool and dry.

   8 min

Plastic or paper

Clear plastic sleeves of polyester, polypropylene or polyethylene let you see the image without taking it out, which saves wear. They should be uncoated, with no plasticizers, and not matte or frosted, which can scratch. Plastic belongs only in a dry, steady room, since it can trap moisture and make the image stick to the sleeve. Paper is opaque and breathes, but you have to take the film out to look at it.

Nitrate film

Nitrate was most common from about 1910 to 1950, for still negatives and motion picture film. Paper photographs are never nitrate. Deteriorated nitrate is highly flammable, and its fumes irritate the lungs, eyes and skin. If you find it:

• Keep it away from heat, sparks and open flame.
• Store it apart from other photographs and papers, in paper enclosures, never in plastic.
• Don't put it in the trash.
• Ask an archivist or photograph conservator about copying the images and disposing of the film.

Cold storage

Cold storage slows the decay of film. A frost-free household upright freezer can work for a small collection, but the film needs vapor-proof packaging first, and every trip into the freezer to look for something shortens the film's life.