Excellent for watercolor, gouache, pen and ink, acrylics, and calligraphy Convenient blocks of watercolor paper eliminate the need for stretching. Mould-made paper is acid-free, chlorine-free, and made of 100% cotton fibers for extra strength and stability. Paper is tub-sized in natural gelatin and air-dried. Resists scrubbing, scratching, and erasing while keeping the original intensity of the watercolor. Each block consists of pre-stitched sheets of paper that are glued together along all 4 edges, and supported by a rigid backing. The top sheet is easily separated from the block by inserting a knife under the sheet and running it around the edges. No optical brighteners are used. Natural white color will not yellow with age. Arches(R) Aquarelle Watercolor Block, 140 Lb, Rough Press, 9in. x 12in. is one of many available through Office Depot. Made by Arches.