Brustro art masking fluid protects the whites of the paper while working with watercolous inks and gouache. To be applied with a brush. It is water soluble when wet and waterproof on drying. Paints are to be applied once the masking fluid dries and to be peeled after the paint dries completely by simply rubbing the gum with fingers or eraser to reveal the masked parts. To be applied with a brush. It is water soluble when wet and waterproof on drying.