Daniel Smith Watercolor Masking Fluid is easy to use with the bottle applicator, the included 5, fine-point applicator tips or with an inexpensive brush. Masking Fluid makes an impervious barrier to protect your watercolor paper and preserve the white areas by blocking watercolor washes from flowing into areas you don't want leaving crisp, clean edges. This masking Fluid applies as an off-white color and dries to a transparent caramel color so that you can see it while working, and still be unobtrusive while working on your painting.