Buffered vs. Unbuffered
Calcium carbonate (chalk) is often added to paper pulp during the paper making process as a buffering agent. This buffering agent raises the pH level of the paper to the alkaline side of the scale (see below). You can measure pH levels using our . The addition of 3% calcium carbonate provides a pH of approximately 8.5 in paper, making it non-acidic. The reservoir of calcium carbonate also helps neutralize other acids in the environment that would normally make any paper become acidic over time.
Most items in storage, especially in the collectibles arena, would benefit from storage in a buffered enclosure. This is especially true for the vast majority of paper items. Because of its ability to neutralize acids and extend the life of paper, photographs, textiles, and artifacts, buffering is more often than not a benefit in interleaving tissue, storage boxes, folders, and other paper enclosures. For most photographic materials, including black and white prints, color prints, and albumen prints, either buffered or unbuffered enclosures are satisfactory. There are, however, some exceptions.
At one time, it was believed that photographs stored in buffered enclosures might be adversely affected by buffering. This is no longer believed to be true except for a couple of specific types of photographs. With dye transfer prints and cyanotypes, unbuffered enclosures should be used. The image substance of both these print types can be harmed by alkalinity.
The other concern over buffering comes from the inclusion of protein-based materials in buffered enclosures. It is generally believed that materials that come from animals should be stored in unbuffered enclosures or at least should not come in contact with buffered materials. These items include silk, wool, leather, feathers, animal specimens, horsehair, etc. The same can be said of blueprints as well.