by Sharon Partridge for the Colorado Preservation Alliance
Last Update: June 2003
Photographs are treasured by all of us. Our baby and wedding pictures evoke memories that are priceless and the picture of Great-aunt Matilda may tell us more about her than all the documents we’ve amassed in genealogy searches. As historical artifacts, they preserve information that didn’t seem important at the time (What were working cowboys wearing; does a crowd scene show that Americans really have gotten taller; or does that sign say that chicken was 10 cents a pound?). For all the pleasure and value of photographs, they are amazingly fragile and must be well treated if they are to survive.
Each photograph is composed of at least three parts. A support layer may be tin, glass, leather, paper or plastic. This backing can curve or be broken depending on the kind of storage used. The binding layer holds the image to the support and is usually gelatin but may be albumen (egg white) or collodion. These organic binders are very attractive to insects. High humidity causes gelatin to soften and become sticky while low humidity may dry out the binder. If the humidity is high enough (over 60% RH) mold will develop which will damage the image and is very difficult to treat. While it is recommended that photographs be kept at a low temperature, remember that rapidly- changing temperatures (such as removing photos from refrigeration to room temperature for viewing) will cause condensation and make the pictures damp or even cause water spots. Humidity also combines with air pollution to produce nitric and sulfuric acids which damage every layer of a photograph. The final part of a picture is the image, made of silver, color dyes, or pigment particles suspended in the binder. This layer is most damaged by light. Framed photographs that are exposed to sunlight or incandescent light will fade alarmingly quickly. Slides that are projected for minutes at a time will be noticeably fainter.
Heat speeds up any chemical reaction, including the deterioration of photographs, and light produces heat; this is particularly true for color photographs. The color will deteriorate more slowly if the photographs are kept in the dark, but the color pigmentation is inherently unstable and will change (I have lovely pictures of the yellow sky in London although I remember it blue.) even if the image lasts.
Ideal storage conditions for photographs are 65-70 degrees with minimal fluctuations and a relative humidity of 3O% with no light. Stacking pictures can cause them to stick together (remember that gelatin?), and loose pictures tend to curl. Unsealed wooden shelving or boxes produce harmful gases. The storage container should be of an inert material, i.e. acid-free cardboard or paper or one of the recommended plastics (see below).
The following suggestions help make your pictures available and long-lasting. Keep your framed pictures away from sunlight and make sure the matting is acid-free. Photo albums should have acid-free (but not buffered) paper or, if you use the plastic sleeve albums, make sure the plastic is polyester, polyethylene, polypropylene or triacetate, NEVER polyvinyl chloride (PVC). Glues from labels or tape or “sticky page” albums can interact with the chemicals in the image. Those “sticky page” contact albums, popular in drug stores, have acidic pages, a pressure sensitive (like tape)adhesive layer and polyvinyl overlays that chemically interact with the image. They are a death sentence for your photographs.
Writing on pictures is very damaging. Ink can come off on adjacent photos, fade, or “bleed” through the image-holding layer and destroy the photo. If you must write on your photos use pencil to write on the edge or in a corner. It is much better to write on the sleeve or album page but still use pencil or permanent ink, not ball-point. Bare fingers (even clean ones) make indelible marks on photographs and negatives. Never touch the image. Professionals use white cotton gloves when they handle photos. Plastic sleeve albums, if they are the right kind of plastic, provide protection from handling.
Even benign neglect is better for your photographs than the wrong treatment. Although checking the chemistry of plastics or hunting for acid-free pages will require extra effort, the life span of your photographs depend on that extra effort. If they are available to add to the historic record or to bring pleasure to your heirs, it will be because you cared.