Why Photos Deteriorate

Photographic film and papers are composed of three parts:

• A support layer made from tin, glass, paper or plastic.

• An "emulsion" or "binder" layer that holds the final image material or image-forming substance (usually gelatin).

• An imaging material suspended in the emulsion layer (silver, color dyes or color pigment particles). 

There are a number of external elements that contribute to deterioration of film and photographs:

• Temperature and relative humidity - High humidity causes the gelatin binder to become soft and sticky, making it vulnerable to mechanical damage and image deterioration. High temperature speeds the rate of deterioration and, together with high humidity, contributes to growth of mold and fungi. Low humidity causes the binder to shrink and crack and the secondary support to curl. Excessive fluctuations in temperature and humidity can cause structural damage, such as cracking.

• Light - Modern, well-processed black and white prints are essentially stable to moderate light levels, however historical photographs and color materials should be kept at lower light levels

• Ultraviolet light - Direct exposure to sunlight or standard fluorescent light, which are high in UV, can cause fading and discoloration within a few years. Keep displayed photos out of direct sunlight, mount them behind a UV filter, or use low-UV-emitting bulbs or UV-absorbing fluorescent bulb sleeves. Better yet, make a digital copy for display and store the original.

•  Wood and paper products - Many wood and paper products contain acids, bleaches and other chemicals that can damage a photograph over time. Only acid-free or "archival" paper products should come in contact with your photos.

• Adhesives and rubber - Most adhesives, including the rubber cement used in "magnetic" photo albums, contain chemicals such as PVC that will harm photographs. Rubber bands can have the same effect.

• Air pollutants - Nitrogen oxides (from combustion) and ozone chemically interact with silver, causing fading. Particulate matter  can be greasy, abrasive and biologically active. Nitrogen and sulfur dioxide from combustion of fossil fuels react with water in the atmosphere to produce nitric and sulfuric acid that can cause silver images to fade and make support materials brittle. Environmental fumes from paints, poor quality paper and plastics, and cleaning solvents can cause images to oxidize and fade.

• Vermin - Insects and rodents will eat photographic materials and foul them with droppings. 

• Hard or sharp surfaces - Hard objects such as paper clips and clamps can damage the surface of prints and negatives. Don't clip photos together.

Poor processing methods such as residual photographic processing chemicals left in the item or the use of exhausted processing chemicals also contribute to the deterioration of black and white film and prints.

Color photographic materials are subject to the same deterioration factors as black and white materials, but in addition they are by nature unstable and not permanent. Organic dyes fade at different rates, even when stored in the dark in proper archival materials. There are three different problems:

• Dark fading occurs regardless of the steps taken to preserve a photo and is unavoidable. Cyan dyes usually fade more quickly, which causes the image to appear too red in color.

• Light fading occurs when materials are exposed to light, such as when on display. The intensity of the light and ultraviolet (UV) rays affect the rate of change.

• Highlight staining is a yellowing of the border and highlight (white) areas that occurs with older photographic papers.