Definitions for "Acid-free"
Material that does not contain acid, whether it be acid-free naturally or one that has been neutralized with the use of calcium.
A term loosely used for papers and other materials that are often pH neutral or alkaline buffered; could be any pH from 6 to 11 (Rose and de Torres 1992).
Products with a pH factor of 7 or higher. If acid remains in materials used on layouts, it can react chemically with photographs and accelerate their deterioration.