Masking fluid, also sometimes called liquid frisket, can help an artist retain areas of white in a painting. Apply the masking fluid over the area that you wish to keep white. Apply paint around it. Then, when you remove the masking fluid, the white area will be perfectly preserved. You can remove the dried masking fluid with either your fingers or a clean eraser. There are several different brands of this product. It is commonly available in art supply stores.
Allow the paint to dry completely. Never try to remove masking fluid while the paint and the paper are still damp.
Wash your hands and dry them thoroughly before removing masking fluid.
Rub at the edge of the dry masking fluid with one finger to loosen it.
Grasp the edge of the masking fluid and peel it upward to remove it. It will often come up in one “sheet.”
Use a clean, soft eraser if you have trouble lifting up the masking fluid with your fingers. Rub the eraser over the area to loosen it, then peel it off with your fingers.
Shake the masking fluid bottle before using it.
Never use a good brush to apply masking fluid, as it will ruin the brush. Use inexpensive or old brushes, and wash them well after use.