Arches Watercolour Blocks contain paper made with natural cotton fibres on a cylinder-mould machine. This artist-grade watercolour paper is great for watercolour, gouache, acrylic, and airbrushing. Arches is made with a natural gelatin sizing. These blocks contain 20 sheets of natural white, acid free, 100% cotton paper, and are glued on all 4 sides. This block is 25cm x 36cm hot press 140lb / 300g.