Winsor & Newton Colourless Art Masking Fluid is sn unpigmented fluid which masks work on paper when colour is applied in broad washes. It minimises staining on absorbent paper. Shake well before use and do not apply to damp paper. Do not use on soft sized paper. apply with brush or pen. Ensure fluid is dry before overpainting and do not leave on paper for long periods. Remove by rubbing with an eraser. Wash brush immediately with soapy water.