Q. I store watercolor paper in the clear plastic bags that blankets are sold in, but I dont believe theyre archivally safe. How long will it take before theres damage to my paper, and what will the damage look like?
San Ramon, CA
A. Keeping your watercolor paper in common plastic storage bags isnt a good idea because most have plasticizers in them (to make the material flexible) that are often acidic and can stain and discolor the paper. This kind of damage is easily visible—probably first around the edges of the paper—and it could occur in as little as six months. Instead of keeping your watercolor paper in these bags, you can store it in the paper or plastic bags that larger quantities of paper come wrapped in, or try wrapping the paper in Mylar plastic, which is inert and wont stain the paper.
If you live in a hot and humid climate, however, be sure to keep the paper in an air-conditioned room or youll run the risk of mold growth, especially in a sealed storage envelope. Ive stored my watercolor paper on an open shelf (so that air can circulate around it) that was first lined with a piece of acid-free matboard, and then placed a loose piece of matboard on the top of the stack, and this system has worked well for me. Metal shelves are better than wooden shelves in this case because the metal wont create an acidic environment for the paper.