Frequently Used Archival Terms & What They Mean

Throughout this website, we use a number of basic archival terms that may be unfamiliar to even the advanced personal collector. For these customers, we offer the following discussion of terms used liberally in product descriptions throughout the site. They are not intended as a technical definition, but rather, to provide a general understanding of the concepts as they relate to archival materials. ArchivalSuppliers.Com offers free in-depth information on a variety of basic preservation techniques prepared by reknowned experts and preservation scientists, that are written in easy to understand language and in layman's terms. See "Free Articles on Preservation" on the left menu bar for a description of these topics.

Acid-Free: Materials with a pH of 7.0 or higher are considered acid-free. Acid-free materials can be either buffered or unbuffered. Buffering agents typically raise the pH of a material to 8.0 or higher. Unbuffered materials can become acidic over time by the absorbtion of acids from the environment.

Archival (Archival Quality): This non-technical term suggests that a material is safe for long term storage and does not contain any chemicals that could adversely affect a collection. The phrase is not quantifiable or standardized, and therefore should not be considered, independently, as a guarantee of acceptable storage criteria.

Archival Polyester: Mylar D, long recognized as the premier brand of clear polyester for preservation purposes, was recently discontinued by the manufacturer. A variety of additional brands of polyester of equal quality remain available. The AstuteCollector.Com uses only the highest grades of polyester in creating it's variety of polyester enclosures.

Buffering: Paper and paperboard products are divided between buffered and unbuffered. Calcium carbonate is the preferred buffering agent of preservation professionals. The buffering agent helps neutralize acids in the environment and help to prevent those acids from attacking your collections. Because of concerns over the affect of buffering agents on certain animal bye products such as wool, leather and silk, unbuffered paper and paperboards are often preferred for storing these materials as well as certain rare photographic collections. Note: Unbuffered materials can absorb acids from the environment and can, eventually become acidic themselves.

Calcium Carbonate: The preferred buffering agent of preservation professionals, Calcium Carbonate is added to paper pulp during the paper making process in order to neutralize acids. It's prescence in folders, boxes, and other enclosures helps ensure that acids in the environment are neutralized.

Lignin (Lignin-Free): Lignin is a naturally occuring substance found in plants and wood pulp. Lignin is thought to contribute to the early degradation of paper and is often removed during the pulping process to create higher grade paper.

PAT (Photo Activity Test): The PAT is an accelerated aging test that predicts the interaction between enclosures and photographic images and can be used to determine possible photographic activity caused by components of those enclosures including adhesives, inks, etc.

Polyvinyl Chloride (PVC): This is a plastic that can emit damaging hydrochloric acids as it degrades, causing damage to materials stored within. PVC often emits a strong odor such as that given off by a new plastic shower curtain.

Caliper: Caliper points, or simply points, is a unit for measuring the thickness of paper. One caliper point is equal to one one-thousandth of an inch.

Grain: The orientation of fibers in paper. Paper has a natural tendency to bend "with the grain", usually making it easy to determine what grain you're working with. Grain can be either short or long, depending on whether it's going on the long or short side of the paper dimensions.

Stock: A term referring to bulk paper or board materials.

Basis Weight: The weight of one ream (500 sheets) of paper, expressed in pounds.