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 & preserve the white areas by blocking watercolor washes from flowing into areas you dont want leaving crisp, clean edges. This masking Fluid applies as an off-white color & dries to a transparent caramel color so that you can see it while working, & still be unobtrusive while working on your painting.