Tips for using watercolor masking fluid

One of my favorite tools in my paint box is masking fluid, also known as liquid frisket. Masking fluid is a liquid rubber product that is used by watercolor painters as a water resist - in other words, it preserves the white of the paper and protects it from paint. These tips will help you use your masking fluid well and get the maximum benefits for your paintings.

1. Masking fluid that is old or contaminated will be difficult or even impossible to remove from paper. For best results use fresh fluid, and write the date on the bottle when it is first opened. Discard any unused products after one year, or sooner if the product has become difficult to remove from your paper or if it's colorant  has left a stain on your paper. Also, paper that is very old will have deteriorated sizing, and that, too, will affect how your masking fluid adheres. Always use fresh products for the best results. 

2. Never EVER shake bottles of masking fluid, it will incorporate air into the fluid which will shorten the shelf life of the product, and make it more difficult to use. Instead, gently swirl or stir the liquid until thoroughly mixed. Adding a pair of small glass beads, marbles, or steel ball bearings into the masking fluid’s jar will help you to mix the fluid easier.

3. To apply the fluid, use a brush that has plastic bristles. The kind that are often found in dollar stores in the children’s or toy section, and usually come in a package of a dozen or so for around a dollar. The stiff plastic bristles allow for maximum control, and can be trimmed with scissors to any needed shape. The plastic bristles do not absorb the fluid, making it easier to clean and reuse. 

4. Apply masking fluid generously. The thicker you apply it, the easier it will be to peel it off later. Thinly applied masking fluid will be difficult to remove.

5. Even with the plastic brushes, it is still best to rub a little liquid soap into the bristles before using them with masking fluid. The soap creates a barrier between the brush and fluid, and makes it easier to clean.

6. Make sure your paper is perfectly dry before applying or removing masking fluid. Never apply it to wet or damp paper, and never try to remove it from wet or damp paper.

7. If you spill or spatter masking fluid somewhere where you don’t want it (such as on your workbench, floor, or other areas of your painting), don’t try to wipe it up. You’ll only end up rubbing it into the surface, making it even more difficult to remove. Instead, let it dry completely and then peel it off.

8. Once you’ve applied the fluid to your paper, don’t leave it on for more than a week. The longer it’s there; the harder it will be to remove. Also, heat will harden masking fluid and make it more difficult to remove, so don’t leave your painting in a hot place or apply heat from a hair dryer while the masking fluid is on your paper.

9. When you’re ready to remove the masking fluid, use a rubber pick-up tool. This inexpensive square tool is made of crepe (aka: gum) rubber and will stick to the dried mask to pull it off your paper with little effort and no damage. 

10. Exposing your masking fluid to air, water, soap, and other contaminants will cause it to go bad faster, so the more you use it -- the faster your bottle of fluid will deteriorate. Decant your fluid into a smaller nail polish bottle to keep the large bottle fresh longer. The nail polish bottle already has mixing beads and a self storing plastic brush that never needs cleaning. It's also a perfect size for traveling. 

(Masking fluid decanted into a nail polish bottle)

This photo shows plastic brushes, steel ball bearings, masking fluid (aka: liquid frisket), and a rubber pick-up tool. To see how masking fluid is used, click here to see a step-by-step tutorial of one of my recent maritime paintings...

Watch this short video for more masking fluid tips!