This acid-free paper is ideal for watercolour, gouache, ink, and acrylic, and strong enough to handle multiple washes of colour without damage to the surface. Natural white 140lb/ 300gsm acid-free paper Arches Watercolour is professional grade paper of the highest quality. Cylinder mould-made, 100% cotton, neutral pH. Internally and externally tub sized with natural gelatin. Contains an antimicrobial agent to help resist mildew. Acid-free, buffered with calcium carbonate and gelatin sized.