[The following posting is based on “Critical Factors for Photo Book Preservation,” which was presented at the 63rd I3A Annual Conference, Monterey, CA, November 10, 2009]
The lifetime of photographic prints is typically dependent on four factors: light, air pollution, heat, and humidity. Any attempt to define how long a print may last must take these four factors into account. For example, saying that a print will last 20 years when exposed to light is meaningless, if air pollution destroys the print in six months. Many of the early lifetime estimates for digital prints were very misleading because the estimates failed to take all four factors into account.
For photo books, light and air pollution are not generally significant factors. Photo books are typically kept closed and on a shelf. Under these conditions, light and air pollution have only a very small effect. Instead, photo books are vulnerable to damage from handling, including failure of the binding system and abrasion of the printed image. Photo book stability is then dependent on these four factors: durability, abrasion resistance, heat, and humidity.
Other factors that affect photo book stability are either less critical or can be controlled in other ways. These factors include light, air pollution, water, spill resistance, mold/insect resistance, and folding/tear resistance.
Creative Memories addresses each factor during the product development process. We use a stitched binding to ensure that hard-cover books are durable, unlike other manufacturers that may omit this step. For soft cover books we use an adhesive that is significantly more stable than the hot melt adhesives that used elsewhere, which may fail over time (see photo below).
Abrasion resistance is also critical. We use paper and ink that resist abrasion. The difference in between three papers can be significant (see below). Finally, we laminate hard-cover StoryBooks to ensure that they will last as long as possible.
The length of time that a photo will last if it is properly store in the dark is determined by its stability to heat. For Creative Memories photo books, the main change is yellowing of the paper over time; consequently, our photo books will last an extremely long period of time in the dark, from 100-300 years.
Humidity is also important, as we cannot control the environment where our photo books may be stored, particularly in tropical climates. Humidity may result in book warp, ink movement, or pages sticking together. We test all photo books at 20% and 80% RH to ensure that changes in humidity will not damage our photo books.
Durability, abrasion resistance, and heat and humidity resistance are the factors that determine photo book stability. Permanence also depends on materials and the production process. Consequently, environmental and physical tests are the only way to ensure permanence and make photo books a preservation solution for the future.