What is Masking Fluid?

Sennelier Masking Fluid

Masking Fluid is a latex based liquid that, when applied to absorbent surfaces, repels moisture and prevents watercolours, inks and gouache from being absorbed. For instance, figures in a foreground can be masked whilst a wash of sky or other background colour is painted, leaving the paper white to allow for the foreground to be painted.

Watercolour with masking fluid applied

After sketching out your drawing, apply your masking fluid to the areas you want to mask. Apply with a colour shaper or old or cheap brush as the fluid is difficult to clean off brushes and you don’t want to ruin any good ones. Give the area quite a generous covering as it easier to take off a thicker layer than a very thin one that may adhere to the paper more than you want. Ensure that it is dry before you start adding your washes.

Masking Fluid

You can continue to add detail knowing that your masked area is protected. It is not a good idea to leave Masking Fluid on for very long periods – over a day – but is fine for a good few hours if required to get all your background detail in.

Removing Masking Fluid

Only once the background is dry should you attempt to remove the Masking Fluid. This should be done by rubbing the dried gum with a clean finger or a putty rubber. It may take a little while to get the gum to start moving but, once it has, it is very easy to rub and peel it away.

White, clean paper where Masking Fluid had been applied