What is masking fluid?
Masking fluid, also known as liquid frisket, is a liquid latex-based product that is very effective at keeping small areas and thin lines white when painting on watercolor paper. The liquid latex prevents the paint from reaching the paper. When the artist is done painting, the masking fluid is peeled off to expose the white paper left untouched.
Artists use it to preserve areas of paper that they don’t want to paint. If a shape is large, we can easily paint around it and wouldn’t use masking fluid, but if a shape is small, such as reflections in glass or whiskers on a cat, by applying masking fluid first we protect those shapes from being painted. In essence we are sealing that shape of paper with this gummy mask. When artists are done painting, they can lift off the masking fluid (with their finger or a rubber cement remover) and the whites of the paper will show brightly.
There are a lot of brands of masking fluid. Most dry clear or with a slightly yellow hue but it is also sold in blue and orange and brighter yellow as some artists prefer to be able to see where it has been applied on their painting. I prefer the clear or slightly colored masking fluid as I find that the brighter ones can throw off my color choices as I paint.
My favorites masking materials and tools include:
Masking fluid is by Pébéo and the Incredible White Mask
I also really like these masking fluid markers: the Molotow GRAFX Masking Fluid Pump Marker, 2mm and the Pebeo Drawing Gum Marker .7mm-Natural Latex, 0,7 mm
As for tools for applying masking fluid I prefer these COMIART Double Head Clay Shapers and these FASHIONROAD Art Ruling Pens in addition to a few cheap brushes.
Rubber Cement Pick-up (handy for removing mask)
When do you use masking fluid?
You use masking fluid in two ways: to preserve the pure white of your watercolor paper for light highlights or to preserve a shape that has already painted in an area where you want to darken around that shape, such as a light blue highlight in a dark blue marble for example.
When you mask on top of colors, just know that there’s always a chance that the painted color might lift off a bit when you remove the masking.
Masking fluid dries out quickly. It will start gumming up even as you are using it which makes applying it tricky.
Tips for working with masking fluid:
Never ever apply masking fluid to paper or paint that is wet or even slightly damp. If you do, you will not be able to get that masking fluid off of your paper. The latex, water and paper bond and the masking will end up sticking to your paper, looking like gummy bumps, and will continue to yellow in time. Apply masking fluid only to paper and painted areas that are 100% dry.
Try out different tools for applying the masking fluid, especially if crisp edges and precise shapes are important for your subject. Artists use ruling pens, skewers, embossing stylus and anything else they can think of to apply masking fluid. And of course brushes. Don’t be casual about applying the masking fluid. It creates very visible hard edges against your paint and softening edges or mistakes is difficult at best.
Always use a cheap brush if you are masking with a brush. Once that latex gets into the bristles of a brush, it will definitely be ruined.
No matter which tool you use to apply the masking fluid, keep it clean as the masking will start to gum up on the tip of your brush or other tool quickly, making precise work difficult if not impossible. Keep a cup of water with some dish soap in it and dip your tool into that water between masking strokes as needed. When I use a brush,I work a bit of dish soap into the bristles and dip straight into masking without rinsing out the soap. This seems to keep the masking from gumming up as quickly and buys me more time in applying the fluid evenly.
Do not shake your bottle of masking fluid. Even though some bottles direct you to shake it, don’t. Shaking it makes all the little particles of latex latch onto each other and the masking fluid will quickly become one big ball of gummy unusable latex. Instead, tilt your bottle gently upside down just one or two times before using.
Cocktail, 27 x 36 in. / 69 x 91 cm.
Never never try to remove masking fluid unless the masking fluid, the paper and the paint are 100% dry. It’s a bit tricky to know when the masking is dry because it remains tacky to the touch even when it is dry. How long masking takes to dry depends on several variables: how thickly you applied it, how humid or dry the room is that you are painting in, and the temperature. The hotter, the dryer and the thinner your application, the more quickly the mask will dry. Give it at least 20 minutes but longer if you applied it thickly or you are working in humid or cooler conditions.
Remove the masking fluid within a week or two. The longer you leave it on your paper, the harder it can be to take off. If you used one of the colored masking fluids, the more likely they might tint your paper permanently. I’ve had students who discovered their paper was tinted blue or orange, depending on the color of the mask they used, even if they removed it within a few days.
Air will cause masking fluid to dry out quickly so if you have a lot of masking to do, pour out a small amount into a bowl and close the bottle to keep your entire stash from from drying out. When you store the masking fluid in your studio, make sure the top is secure and flip the masking fluid container upside down. Store it upside down, preventing air from reaching the lid of the container while being stored and thus slowing down the drying out process.
If you get masking fluid somewhere where you don’t want it (another area of your painting, your clothing, carpet, furniture…), do not try to clean it up while it is still wet. DO NOT use water to try to clean it up. Let it dry out completely. Then just pull it off the surface. It will come right off.
Original/Classic, 24 x 36 in. / 61 x 91 cm.
Masking fluid does get old. If it is no longer fluid enough to use, don’t add water to it to try to make it more fluid. While yes, adding water will liquify it again briefly, it is also going to dilute the effectiveness of the masking fluid and will likely glue itself to your paper. Even if you manage to peel it off your paper you will likely find that diluting it made it too porous to keep all the paint from working its way to the paper. You’ll likely ruin your painting. Just toss out old masking fluid and get yourself a fresh bottle.
Masking fluid creates very sharp edges around the shapes you mask. Many artists don’t use masking for this reason. If you don’t want sharp edges and if the shape is not too small, you can soften the edges with a damp brush (but it is a lot of work). If the shape you want to preserve is big enough to paint around without masking, I recommend not masking. If the shapes are too small to paint around or we want to paint in layers and it would be too tedious to paint around specific shapes multiple times, then masking fluid is a good solution.
Final tip: never apply or remove masking fluid unless your paper, you paint and the masking fluid are 100% dry. I know I’ve said this already. It bears repeating.
Masking fluid is great for preserving the white of the paper as well as preserving light colors. These saved light shapes can add sparkle, interest and depth to our paintings. Like all techniques, it takes practice to get comfortable with using masking. Don’t panic if it doesn’t look the way you had hoped. Get familiar with masking and different ways to apply it before using it on a painting.
Below is a video I made exploring different masking fluids and various tools for applying it.
Lovers at Sea, 30 x 22 in. / 76 x 56 cm.
Winter Bird, 19 x 14 in. / 48 x 36 cm.