Many people still don’t realize that their old photos, important papers, news clippings, etc are slowly being destroyed by the boxes, albums, and other containers they are stored in. I’ve seen precious photographs literally stuck to photo album pages, torn when removed, or so brittle they fell apart. Nothing is more sad than to know that a rare and precious picture of your loved one, that you thought was safe and sound, has been destroyed.
Paper is made from wood-based pulp and contains lignin, which causes paper to yellow and deteriorate. When paper is exposed to heat or light, lignin in the paper causes the molecules to break down at a faster rate.
Lignin is not an acid, but it gives off acid as it deteriorates. Therefore if you have a paper that is only acid free, but still contains lignin, it will become acidic over time.
Chemicals used in the paper making process also leave a residue of acid in the paper. Acid rots the paper away over time. Thankfully acid-free paper has now become the industry standard. But not all paper is acid-free, nor is it lignin-free.
Acid-free paper is treated with calcium or magnesium bicarbonate. The papers made with this process will be preserved for at least 100 years.
Specially designed archival paper that is 100% acid-free is often used for legally significant or historical documents. This type of paper has a longer life span than the 100 years. Typically made of cotton or other fabric material, this paper is more expensive, thicker and is sold through archival supply stores.