Things You'll Need
Old paint brush or glue brush
Rubber cement pickup
Masking techniques are an invaluable way to preserve areas of your watercolor painting. Numerous masking fluids designed specifically for this purpose are available for purchase, but common household rubber cement works just as well. Use rubber cement to keep areas of your painting white that are too intricate to paint around or preserve layers of color previously applied while you add additional colors to surrounding areas. Rubber cement is a flawless masking medium commonly drawn upon by even accomplished watercolor artists.
Paint the initial layer of your watercolor painting, such as a base sky hue or overall background wash. Allow the wash to dry completely.
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Use an old paint brush or glue brush to apply common household rubber cement to the areas of the painting you wish to remain the color of the initial wash. For example, use the rubber cement to block out light areas of clouds or the white-capped tips of waves in a seascape. Allow the rubber cement to dry completely.
Apply a second layer of watercolor paint directly over the masked-out rubber cement-covered areas. The areas of your painting covered in rubber cement will repel the paint while the areas without rubber cement will absorb the paint in a normal fashion. Allow the second layer of wash to dry completely.
Use a rubber cement pickup to gently rub the areas of your painting covered by the rubber cement mask. The rubber cement will begin to rub off the painting, creating small crumbs or balls of rubber cement. Rubber cement pickups can be purchased at most craft stores. If you don't have a rubber cement pickup, your fingers can also be used to gently rub the rubber cement mask off of your painting.
Brush all of the rubber cement mask crumbs off the area. The areas of the painting covered by the rubber cement mask are the color of the initial watercolor wash.
Use rubber cement masking fluid to create a falling snow scene. Drip small amounts of rubber cement onto the sky area of your winter landscape scene. Allow the rubber cement masking fluid to dry before applying a blue-grey wash over the sky. When the wash has dried, remove the small drips of rubber cement masking fluid with your rubber cement pickup, revealing white snowflakes falling gently across the sky.
Never apply a rubber cement mask to a painting that is not completely dry. The rubber cement will seep into the paper and tear it when the mask is removed.
If possible, remove your rubber cement mask as soon as possible after the paint has dried. Leaving the mask on the paper for a long period of time can increase the difficulty of removing the mask.
Be careful which paint brushes you use with the rubber cement masking fluid. Rubber cement can easily ruin an expensive watercolor brush. Some watercolor artists dip their brush in dish soap before dipping it into the rubber cement in order to protect the bristles of the brush. Using a cheap brush you don't mind sacrificing is recommended.