Arches Watercolor Blocks feature a superior quality, 100% cotton rag, natural gelatin sized, mold-made paper. Made in the Arjomari Mills of France since 1492. The paper is bound on all four sides for rigidity and to prevent warping. The sheets are buffered with an anti-microbial agent to help resist mildew. They are available in a convenient assortment of sizes and are ideal for field work.