Acid - Acids can weaken cellulose in paper, board, and cloth, leading to embrittlement. Acids may be introduced in the manufacture of materials and left in intentionally (as in the addition of certain sizing, like starch or glue) or incidentally. Acids may also be introduced by migration from other materials or from atmospheric pollution. Discolouration and embrittlement are attributed to acid.
Acid-free - Material with a pH value of 7.0 or slightly higher. This specifies the absence of acid which can quickly break down paper and photographs.
Buffered Paper- A paper that is pH neutral to begin with and then has a reserve of Alkaline to neutralise any acids as they migrate to the paper
Lingnin - Lignin is a substance that occurs naturally in plant cell walls and therefore in papers made from wood pulp. Lignin has definitely been linked to the discolouration of papers and some experts believe it also contributes to the deterioration of paper. You will have noticed that newsprint turns yellow rapidly, this is because of it's high lignin content. Most photo preservationists believe lignin to be more harmful to photos than acid. Your safest bet is to avoid lignin.
Mylar- Mylar (polyester) is used as a protective clear covering for photos and album pages. Mylar is currently regarded as the highest quality material used for this purpose.
pH Neutral- This term sometimes used instead of acid free. pH neutral is more definitive than acid free, a pH value of 7.0 is neutral.
Polyvinyl Chloride (PVC)- Avoid anything containing PVC. Instead look for items that contain polyethylene Polypropylene, or polyester (such as Mylar, which is considered one of the best materials for archival plastic envelopes and sheet protectors).
Scrapbooking is a craft or hobby that is intertwined with science. Many of us do not know very much about preserving our photos. What is safe, what isn't, and why certain materials should be used and others avoided. Hopefully the following definitions will help you gain a better understanding.