Arches Aquarelle watercolour paper is acid-free and chlorine free. It is made of 100% cotton fibres which provide strength and stability. The paper is tub-sized in natural gelatine and air-dried, it can take scrubbing, scratching and erasing while keeping the original intensity of the watercolour. 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.This block of 20 white sheets of Arches Aquarelle watercolour paper measures 24 x 18in and is glued on four edges. The weight of the paper is 300gsm. Please note, this product has a hot pressed surface. The surface of the paper is extremely smooth, which is ideal for detailed watercolour painting.