Arches Aquarelle watercolour paper is acid-free and chlorine free. It is made of 100% cotton fibres which provide strength and stability and professional archival quality. The paper is tub-sized in natural gelatine and air-dried, so it can take scrubbing, scratching and erasing while keeping the original intensity of the watercolour. It also contains an anti-microbial agent to help resist mildew. Arches Aquarelle uses no optical brighteners so it's natural white colour will not yellow with age and archival value is ensured. Suitable for watercolour, gouache, pen and ink, acrylics and calligraphy.Arches watercolour blocks come in a variety of sizes, surfaces textures, and weights. The convenience of working on a block eliminates the need for stretching. Arches blocks are not only for painting, but also work well for drawing as it provides a sturdy support surface to work on. This block of 20 white sheets of Arches Aquarelle watercolour paper measures 20 x 14 in and is glued on four edges. The weight of the paper is 300gsm.Sizing is important to watercolor paper. It helps the paper accept washes, scratching and erasing without affecting the actual fibers and strength of the paper. Arches is sized with natural gelatin and has been made in France since 1492. Please note, this product has a Not (cold pressed) surface. The surface of the paper is slightly textured, and is not suitable for extremely detailed work. Most painters will find it suitable for most purposes.