Acid Free (Neutral pH)
Papers that are without acid in the pulp. Acid free papers have a pH of 7.0. If prepared properly, papers made from any fiber can be acid free.

Acid Migration
The transfer of acid from an acidic material to a less acidic or neutral-pH material. Occurs when neutral materials are exposed to atmospheric pollutants or when two paper materials come in contact. Acid can also migrate from adhesives, boards, endpapers, protective tissues, paper covers, acidic art supplies, and memorabilia.

An astringent crystalline substance used in rosin sizing to hold paper fibers together; responsible for introducing acid into the paper.

A printing paper with a rough finish but good printing surface, valued in book printing for its high volume characteristics.

Archival Paper
A paper with long-standing qualities, acid free, lignin free, usually with good color retention.

Art Paper
It is a woodfree coated paper.

Ash Content
The amount of residue when a sample of paper is burned under controlled conditions so that all ignitable matter is removed.

The extent to which a paper will take up and hold a liquid.

Absolute/relative moisture
Absolute moisture the absolute moisture of the air is the maximum amount of water vapour which the air can contain before the excess water is released as dew or frost. Absolute moisture is measured in grams per cubic metre. As the temperature falls the air contains less water in grams at the same relative moisture.To understand why the air may be drier or damper, we can consider why someone's beard becomes frosty on a cold winter day, when the air seems to be dry, while water evaporates when we sit in a damp sauna.