Glossary of Terms

ACID (paper) -  
Mechanical pulping of wood-based paper pulp does not allow for the removal of lignin. Lignin is a natural substance that is in plants and trees and helps to make them rigid. As lignin breaks down in paper it converts to acid. The paper will eventually turn yellow and become brittle.
On a scale of 0-14 acid-free paper is a 7. Anything under 7 is considered acidic. During the paper pulping process, the lignin is removed from the pulp. Lignin will break down into acid if left in the pulp. During the pulping process, the more refined the pulp is, the less acidic the paper will be.

ACID MIGRATION - Acid can travel from one item to the next through physical contact. It can also travel travel through the atmosphere in acid vapors.  Either of these processes will make an acid-free item acidic.

Paper with a pH of  of 7 or greater. Also defined as acid-free paper. Acidity and alkalinity on are on opposite ends of the pH scale.

Papers that are made from alpha cellulose (wood pulp),in which the lignin is removed and then are buffered to keep acids in the atmosphere away.

Polyester is a crystal clear material that is used for archival storage of paper products. It is inert and of the highest purity. It will not discolor, adhere to items stored in it or cause damage to items stored in it. This material is approved by the Library of Congress for indefinite storage.

Buffering agents can neutralize acids helping to maintain the pH level of an item. It is also resists migrating acids.
Calcium carbonate is added to paper pulp during the paper making process as a buffering agent. This raises the pH levels of the paper to an Alkaline level of 8.5. It helps neutralize acids in the atmosphere as well as keeps acids from  entering the paper.

Cellulose is an important component of the cell wall of green plants and trees. It is mainly used to produce paper and paper-board and increase its strength. The cellulose content of cotton fiber is 90% and that of wood is 40-50%.

Chemical stability refers to the propensity of a material to resist change whether from its internal structure or outside influences such as air, moisture or heat. 
Conservation of paper refers to the steps taken to improve the current and future stability of paper products. This can be done by repairing the paper itself, improving the chemical structure of  the item as well as improving the storage containers and facilities the paper will conserved in.

Cotton paper is mostly made from cotton rags. The cotton rag has long  fibers which give the paper extra strength and durability. High-quality cotton fiber paper can last hundreds of years without fading or breaking down.

Deacidification is the process of dissolving acids in paper. This can be done by aqueous (liquid) methods or non-aqueous (chemicals) methods.

Encapsulation is a preservation method used for safeguarding a fragile sheet of paper. Place the paper between two sheets of Polyester. This keeps it in an acid-free environment. Seal all four edges of the polyester sheets with acid-free tape.

Inert means that an item is chemically inactive. It remain motionless. Does not interact with other substances. 

Lignin is an important natural substance in green plants and trees. It keeps them strong and water is moved through it to hydrate the plants (trees). However when wood is mechanically pulped for paper, lignin becomes a volatile substance. It  yellows the paper and causes the paper to break down and form destructive acids.


Mil is used in the United States to measure the thickness of various materials.  It is one thousandth of an inch.

Melinex® is an archival polyester film manufactured by DuPont Teijin Films™. 

Mylar is a generic term used when referring to Polyester material. It was a trademarked name for a retired DuPont polyester.

(Polyfluoroalkyl and Polyfluoroalkyl) are a group of chemical substances that studies have shown that exposure to in the environment may be linked to harmful health effects in humans and animals. These substances are known as forever chemicals.


A substance that is neither acidic nor alkaline is considered pH neutral. More acidic papers have a lower pH; a higher pH means it is acid-free. On a scale of 0-14, 7 is pH neutral.

Polyester (PET) is a clear film manufactured by DuPont Teijin Films. It is as clear as glass, has outstanding structural strength, shape stability and chemical resistance. Used for archival storage of paper products. This material does not contain PFSAs (forever chemicals).

Polyethylene (LDPE) is a clear soft film used for making poly (plastic) bags. It is very strong, flexible and a decent water barrier. It seals well when the correct heat is applied. This material does not contain PFSAs (forever chemicals).

Polypropylene (PP) is a crystal clear film usedfor making poly (plastic) bags. It has excellent contact clarity as well as a sheen. It is resistant to moisture absorption, has good chemical resistance and is slightly rigid. This material does not contain PFSAs (forever chemicals).

Polyvinyl Chloride (PVC) is a clear film that can be manufactured into both a flexible film and a rigid sheet. PVC is made flexible by adding plasticizers to it. There  is controversy over the toxicity of PVC at the time of manufacturing and disposal.

Preservation is the act of performing specific activities to halt the deterioration of, as well as to prolong the life of items made from paper. Conservation and preservation definitions are interchangeable.