Masking fluid, also known as maskoid or liquid frisket, is a combination of latex and ammonia that is used by artists to temporarily block out part of a watercolor painting until the surrounding areas have been completed. The masking fluid can then be gently removed so that area can be painted or left white.

Masking fluid is similar in consistency and texture to paper cement/rubber cement glue. Once you apply it to the paper, it dries fairly quickly, developing a rubbery texture that you can rub off with your finger.

I usually use a paintbrush to apply the fluid, though I make sure it is a very old and inexpensive brush (such as a child’s brush), as it is very difficult to clean afterward. I have never been able to clean one thoroughly enough to use it again, unless it’s to apply more masking fluid.

Although there are a number of different brands of masking fluid, I’ve only tried two so far — The Incredible White Mask and Grumbacher’s Miskit Liquid Frisket. I prefer the Incredible White Mask to Grumbacher’s brand, but I purchased the Miskit from a seller on ebay, so maybe it was an older solution and that’s why it didn’t work as well.

When using masking fluid, you don’t have to worry about the paint covering the area where it was applied – it will remain white or the color you had previously painted. This allows you to create smooth and even washes of background color without having to paint around an object in the foreground. On the other hand, the fluid will often leave hard edges on the area covered that may be difficult to soften. The best way to find out — give it a try to see what you think!

Before you start, be sure to check out this video on using masking fluid with watercolors.