This is a 15 pack of Pearl White 4-Ply 20 x 24" Conservation Mat Board from Archival Methods. Made from alpha-cellulose pulp from purified wood fiber, it's more economical to produce then traditional cotton paper. However, the long-term stability is the same. This kind of paper is famous for being safe to use with paper artwork, photographs and documents.
It is acid- and lignin-free and uses alkaline or neutral sizing. The boards are buffered with calcium carbonate for added protection and longer life. Pearl White has a warm tonality as opposed to Archival Method's Bright White Museum Board. It has a similar look as antique white but with less yellow. This board has similar characteristics to cotton pulp paper with a surface that is almost the same.