Both Light Impressions and Conservation Resources have good materials. If
you are in a larger city, and have a business license, may I suggest
visiting a few wholesale framing suppliers. I think I pay about $6US for
either buffered or unbuffered Strathmore 4 ply museum board. Plus you have
no "shipping" charges. In California, the wholesalers won't sell to you
without a resale (tax) number.
tomf2468@pipeline.com (Tom Ferguson)