We stock 2 grades of BACKING BOARDS to protect your theater playbills: 1. Chipboard - pH neutral board contains acid but is .30 point thick and an excellent choice for short-term storage. White on one side. SUPER economical. 2. Standard Acid-free is acid-free all the way through. Acid-free board can trap migrating acids in paper and neutralize it. Use our .028 point board for intermediate to long-term storage. White on both sides.