Winsor & Newton Art Masking Fluid is a colorless or pale yellow liquid for masking areas of work to be protected from subsequent washes of color. Dries to a removable, water-impervious film. Colorless Masking Fluid contains no pigment, eliminating the risk of staining paper.
Permanent Masking Medium is also used to mask specific areas of paper, making them resistant to water, and can be intermixed with watercolors. Unlike Art Masking Fluid, Permanent Masking Medium is not removable.