Created with the needs of high-end preservation mounting in mind, this Acid-Free foamboard is perfect for archiving and framing. The center is made from extruded polystyrene with acid free paper facers. Each board has two mounting surfaces with no harmful gasses or pollutants. Warp resistant, and dent resistant to retain a consistent thickness. Perfect for artists, photographers, and professional or home framers alike. Made in compliance with PAT standard, the liners have a ph value ranging from 7.5 to 9.5 and are buffered with 3% to 5% calcium carbonate reserve to maintain its acid-free characteristics for longer. Liners are made from 100% high alpha cellulose virgin pulp; free from post-consumer materials.