acid free paper
Acid-free paper is unlike any traditional paper substance. ... Paper that is derived from these pulps degrades over a number of years unless the acidity is neutralized. If this neutralization does not occur, the paper created becomes very brittle and weak, which can accompany a yellowish change in colour. ... Acid-free paper has a pH factor of 7. ... Acid-free paper manufacturers achieve this neutral pH by neutralizing the acids with an alkaline buffer such as calcium carbonate or magnesium bicarbonate.