Storing photographs and negatives

Environment: the most important decision

The Library of Congress considers a good environment to be probably the most important measure for protecting photographs. It recommends:

• relative humidity of 30–50%, fluctuating by less than 5% in 24 hours. According to the LoC, humidity is the most important factor for most photographic prints,
• a temperature of 70 °F (about 21 °C) or lower,
• for colour photographs and negatives, cold storage at 40 °F (about 4 °C) or lower, because for them temperature is the deciding factor,
• limiting light and polluted air.

The NEDCC adds that the rate of chemical decay of most photographic materials roughly doubles with every 10 °F rise in temperature (about 5.6 °C). Humidity that is too low, on the other hand, dries some materials out and makes them brittle.

Where at home, and where not

Not here	Why	Better
the loft	hot in summer	a cupboard in a lived-in room
the cellar	damp, risk of flooding and mould	a shelf off the floor
against an outside wall	condensation, fluctuations	against an inside wall
near a radiator, fireplace or air vent	heat and fluctuations	away from heat sources
the bathroom	humidity	a dry room

When taking photographs out of cold storage, the NEDCC advises letting them acclimatise overnight in a closed container (a polystyrene box, for instance), so that moisture does not condense on them.

Enclosures: ISO 18902 and the PAT

Every photograph or negative belongs in a primary enclosure: an envelope, sleeve or pocket. The Library of Congress states that an enclosure meant to be safe for photographs must meet the physical and chemical requirements of ISO 18902, including passing the PAT (Photographic Activity Test, ISO 18916). Suppliers usually say so.

Paper enclosures	Plastic enclosures
opaque, protect from light	transparent, so the photograph can be seen without taking it out
breathable, can be labelled in pencil	unsuitable at high humidity (above 70% the emulsion can stick)
buffered (pH 8.5) and unbuffered (pH 7)	only uncoated polyester, polyethylene or polypropylene
buffered not for dye transfer prints and cyanotypes	not for nitrate and acetate negatives

Put the enclosures in boxes made of photo-safe material. A box evens out swings in humidity and temperature and protects against light and dust.

Labelling

• Write on the enclosure, not on the photograph.
• If you must write on the photograph, use a soft graphite pencil on the back, near the edge.
• Do not use paper clips, rubber bands, sticky notes, sticky tape or glue.

Albums

The Library of Congress recommends not using pressure-sensitive tapes, glues or other adhesives on photographs. Old albums with “self-adhesive” pages under a plastic film are therefore risky for photographs: the adhesive is in direct contact with the back of the photograph, and the film may not meet the requirements for enclosures. If the photographs come away from the pages without force, move them into PAT-tested enclosures. If they don’t, do not tear them off; scan the whole page and consult a conservator.

Digital copies

A scan is a second layer of protection. Keep at least three copies on two different types of storage, one of them away from home. Once a year, check that the files still open. The scanning method is in Scanning old photographs.

Displaying originals

Every period of exposure to light puts a strain on a photograph. Display originals briefly, out of direct sunlight and behind UV-filtering glass — or hang a good copy on the wall and keep the original in the dark. See Frames and glazing.