I made a video about the use of liquid mask, but I think I could just as easily tell you the main points with written word.
Before I start, I get a cup of water and squeeze in a little dish soap. I use a green dish soap mainly so that I can see it as it goes into the water. This helps me know how much I’ve added. I would say give the dish soap bottle one brief squeeze. I gently stir it into the water with the stick end of a paint brush.
Select a brush that you could throw away after this, if necessary, if any masking fluid adheres to the bristles.
Most masking fluid has a slight tint to it. This does not really harm the paper or cause discoloration. It does help you to see it against the white of the paper so you know exactly where you’ve applied it.
To prep the bottle of mask, never shake it to mix it. A better idea is to simply stir it with the stick end of a paint brush. If you shake the bottle, you’ll have a frothy mess when you open the bottle. Better to stir, open the bottle, and see the surface of the mask clearly.
When you’re ready to apply the mask, dip the brush in the water and dish soap solution. This coats the brush with the soap and water so that it protects the bristles from the mask. Now dip the brush into the mask and begin applying it to your paper.
When you’re finished applying the mask, gently rinse the brush off in the soap and water solution. You’ll find that all or nearly all of the liquid mask is cleaned from the brush and you can probably use the brush again.
You can apply frisket with a brush, but you can also use a toothpick if you are trying to achieve a finer line.
Usually I simply leave the paper white where I want white in my painting. I try not to use masking fluid any more often than necessary. However, liquid mask is great for areas that are impractical for trying to paint around. I’m thinking of the flowered pattern on this scarf or the fine hairs you see in the painting. If I had attempted to paint around each flower or hair, it would have taken me months to complete the project.
Once I have applied the masking fluid, I try to paint that area as soon as I can. I may not get to the area for a few days, but I make a conscious area to make that area a priority. The longer you leave masking fluid on the paper, the more likely you are to damage the paper when you lift the mask. It can actually pull up paper fibers. Once that happens, paint won’t take to the paper the way you hope or expect. Another tip is that I don’t use masking fluid that is old. I try to keep a relatively fresh bottle on hand. If you’re unsure about a bottle that you have, do a small test on a piece of paper that’s similar to the type you’re using for your project.
My personal favorite is Winsor & Newton Art Masking Fluid.
When the masking fluid is dry and you’ve done all the painting you need to, it’s time to remove the mask. I use a little rubber square that removes double sided tape. You can also just use your fingertip or you could try using an eraser. The key is to be gentle and try not to disturb the painted area around the mask. Once you begin to lift the mask, continue slowly and carefully so as not to pull up any of the paper fibers. I often get the mask removal started and simply grab if with my fingers and gently and evenly pull it off the paper.
Now you’re free to paint in the masked area, if needed.
I hope these tips are helpful. Good luck to you and happy painting!