Arches watercolor blocks are 100% cotton watercolor paper, with a structure that gives it strength and a characteristic feel. The cylinder mould manufacturing process makes it possible to obtain harmonious and varied grains with rough, cold-pressed and hot-pressed surfaces. The paper is gelatin-sized and then air dried so that colors used retain a fine rendering, even after the surface has been scraped and erased. Its natural whiteness (no optical bleaches), mildew protection and neutral pH mean that the paper has a very long shelf-life. It is an excellent artist quality paper for watercolor, gouache, pen and ink, acrylics or calligraphy. All blocks are 140 lb weight, with 20 sheets per block.