Found this article while I was surfing net last night. But sorry I forgot to save the link...Anyway content as below..
Scrapbook pages are memories given physical form, and a well-crafted scrapbook should keep those memories for generations. To make sure that your scrapbook lasts, it's necessary to choose materials that won't decay, degrade, or color over time. Most important is paper choice. As the base for all your scrapbooking, the paper you use should be durable, permanent, and non-yellowing.
Because they are made of cellulose fiber pulps, most papers naturally contain acidic compounds. These acids can break down the paper over time, making it brittle and weak. For paper to last, its natural acids need to be neutralized or removed. Papers that have undergone this process can be placed in three grades: pH neutral, acid free, and archival.
pH Neutral — Specifically, the term "pH neutral" indicates that the paper has a pH near 7 and is neither acidic nor alkaline. What this usually means is that the manufacturer has added a mild base such as calcium carbonate to neutralize the pulp's natural acids. While this does increase the life of the paper, it is not necessarily permanent. Over time, the acids in the paper can overcome the effects of the base and cause the paper to deteriorate. Storing the paper in acidic cardboard boxes or exposing it to sunlight will accelerate this process.
Acid Free — Papers that are "acid free" usually have a pH ranging from 6 to 8. Papers are acid free either because they are made from naturally neutral fibers like cotton rag or because their acids have been removed during the manufacture process. Although acid free papers can be contaminated by the acidic environment around them, they will generally last for years and are an excellent choice for scrapbooking.
Archival — For extreme long life, "archival" paper is the way to go. While there is no industry standard, archival papers have usually been laboratory tested for chemical stability. They are almost always acid free and buffered against outside contamination. Truly archival paper is permanent enough to last for centuries.
Papers made from wood pulp also naturally contain a compound called lignin. Lignin is the binding material in wood that gives it its rigidity. Unfortunately, lignin also speeds up the deterioration process in paper, causing it to yellow and disintegrate. The most obvious example of this can be seen with newsprint, which can often yellow within the space of a day. It is important that any paper you use be lignin free as well as acid free.