Acid-free - Acid is used in paper manufacturing to break apart the wood fibers and the lignin that holds them together. If acid remains in the materials used for photo albums, the acid can react chemically with photographs and cause their deterioration. Acid-free products have a pH factor of 7.0 or above. It's imperative that all materials (glue, pens, paper, etc.) used in memory albums or scrapbooks be acid-free.
Acid migration - Acid migration is the transfer of acidity from one item to another through physical contact or acidic vapors. If a newspaper clipping is put into an album, the area it touches will eventually turn yellow or brown. A deacidification pH factor spray can be used on acidic papers, or they can be color photocopied onto acid-free papers. Archival quality -
"Archival quality" is a term used to indicate materials which have undergone laboratory analysis to determine that their acidic and buffered content is within safe levels.