Archival Methods Flat Short Top Box 16.5x20.5x5", Gray Smooth plate finish free from knots, shives and abrasive particles. Made from fully bleached, high alpha cellulose pulp. It does not contain any post consumer waste recycled pulp. Paper is free of metal particles, waxes, plasticizers, residual bleach, peroxide, sulfur content is less than 0.0008% reducible sulfur. The lignin content is measured by the phloroglucinol test with a Kappa number of 5 or less. Metallic Impurities, Iron will not exceed 150 ppm and copper shall not exceed 6 ppm. No optical brightening agents are used in the pulp.