These Canson 100 Watercolor Blocks feature 15 mouldmade, 100% cotton sheets that are acid-free and heavily sized for taking repeated reworking. Bound on all four sides, watercolor blocks prevent curling of the sheet while eliminating the need for taping sheets down. After use, your finished art may be removed from the block with a standard razor blade. Most blocks have an exposed area allowing you to locate the bottom of the sheet without harming other sheets. You'll find that a watercolor block can be quite convenient for both field and studio use. Every well-balanced studio should include a watercolor block as part of its available supplies.