Archival Methods Museum Board is made of 100% cotton fiber. Bright white is a neutral tone board, is acid and lignin free and incorporates an alkaline or neutral size. All boards are polished with calcium carbonate. This ensures protection against the destructive effects of acid migration from matte work and from a contaminated environment which could cause the pH of the mat board to decrease (become more acidic) with age. No optical brightening agents are used in the manufacturing of your 100% cotton museum board. 8 ply / 120 points (about 1/8 inch) 100% cotton fiber (99% alpha cellulose). Contains no recycled pulp from post-consumer waste. The paper is free of metal particles, waxes, plasticizers and residual peroxide from bleach. The sulfur content is less than 0.0008% reducible sulfur. The iron content does not exceed 150 ppm and copper does not exceed 6 ppm. No optical brightening agents are used in the pulp. Alkaline size is used for both internal and external size. No aluminum is used in the manufacturing process, buffered with calcium carbonate 2-3% alkaline reserve, pH 9 +/-0.5, acid-free board will not degrade and cause damage to matted artwork board passes The PAT (Photographic Activity Test) ISO IT 18916 (formerly ISO 14523 ANSI IT9.16) Lignin content is Tested by TAPPI 92.9 in-85 and has a Kappa number of less than five. Single-ply sheets are laminated together using natural starch adhesive. Application