Before I knew what resist was I had wondered for years how watercolour artists managed to paint in blank areas. I tend to paint haphazardly so being able to think forward enough to leave huge blank areas like this was far beyond my scope.

Screw forward thinking, resist/masking fuild is awesome!
Basically resist/masking fluid is a slightly gummy paste which you paint on, then you can paint colours over the top and carefully remove it to see the white paper underneath.
You can use it in a number of ways. Here are 4 of them!
Top left: Mask out entire heart
Top right: Mask out the area around heart to make a sharp edge
Bottom left: Mask out little spots on the heart
Bottom right: Mask out an entire heart on a painted area
Once the fluid is dry, paint over the top.
Gently peel the resist off the paper and it leaves it clean underneath. You can see on the bottom right, the top of the heart is messed up because I was too vigorous when removing it and I tore up a little bit of the paper which was still a bit wet. >_<
Let’s do a bigger project with it. I have sketched out a deer and we will mask that out and paint over it. So sketch out main drawing.
Shake up your fluid. I tends to form a skin over the top so you want to make sure it’s a good thin consistency before you paint.
It’s a good idea to have a dedicated brush for working with masking fluid because it tends to be a pain in the arse to clean up and you don’t want to ruin good watercolour brushes.
Begin by masking off the larger areas like the neck. You can see what happens if you use unmixed masking fluid below, it’s lumpy and harder to work with so make sure you mix it well!
I suggest that you thinly outline the area that you want to paint in and then fill in the middles.
If you make a mistake don’t just wipe it off. Wait for it to dry and then gently peel it off and repaint that area.
Any areas you want coloured leave blank.
It can be really difficult to see what you’re doing when painting white on white so I suggest angling your paper while sitting near a window. Leave it to dry very thoroughly before you start painting.
The painting technique we’re going to use for the rest is basically adding a lot of water and then dripping colour on to it.
So soak  the paper with a coat of water. I suggest when doing paintings this wet you should remove the paper from your sketch book and put it on a board so you don’t ruin pages underneath. For this kind of painting you really need to use a heavy grade of paper.
Once your paper is nice and wet, begin by dripping your first colour. I like to start around where the masking is so I can actually see what I’m doing for the rest of it.
Add in a second colour and keep dripping water as you go to keep things wet and easy to move.
Keep layering water and paint.
You can see just how much water is used in these kind of paintings.
Make sure to concentrate on important details like the eyes and pay close attention to the colours there.
Now leave the entire thing to dry very thoroughly. Even if it seems dry I would suggest leaving it over night or else you risk tearing when you remove the resist.
Once it is dry gently peel the edge of the fluid and slowly peel it up. If you can’t find the edge, you can VERY gently use a pin to hook it and then pull up with your fingers.
It should have kind of the consistency of latex eyelash glue. Be super careful around the edges.
Taadaa!
To do this kind of painting you do need to be able to think ahead and almost do things backwards, you need a clear vision of how the picture is going to look in your mind before you begin.
You can see that the lines around the resist are very sharp and clean.
So there you go, now go and paint something fun!
Hopefully you have a decent grasp of how masking fluid works now! Let me know if you have any questions 😀 I’m really enjoying writing this series now, I hope you are all enjoying reading them.