A small group of books were recently found in Rare Books with mold on them. We surveyed the area and found everything that looked even remotely moldy. I cleaned them with alcohol and let them air dry. My theory is these books grew mold because they were in a glass covered book case with no air flow. The space is not humid. I’m hopeful these valuable books – written by Voltaire 1760’s- will not see any more mold growth.