All Paperback books are made with Khadi Rag Papers. Khadi Rag papers - Artist Paper made from 100% long fibered cotton rag, resulting in exceptional strength and durability. They are tub sized (surface sized) with Gelatine. For watercolor and all painting and drawign media. For oil paint prime with gesso or acrylic primer. Acid free. This is a handmade item and is not eligible for return or refund.