The Daler Rowney Watercolour Medium Art Masking Fluid is a professional-grade liquid rubber medium engineered to preserve crisp white highlights and delicate paper details during heavy watercolour or ink washes. It flows smoothly onto the surface and quickly dries into a temporary, water-resistant film that shields your paper from overlapping wet mediums. Once your painting is completely dry, the rubbery mask can be peeled away or rolled off effortlessly using a soft eraser, leaving behind immaculate, hard-edged paper borders.