Winsor & Newton Watercolour Colourless Art Masking Fluid is colourless, non-staining liquid composed of rubber latex for masking areas of work needing protection when colour is applied in broad washes. A removable, colorless liquid, use it for masking areas of work specifically designed for soft sized papers to avoid staining. It is identical to Art Masking Fluid but contains no pigment. Absence of pigment eliminates the risk of staining paper.