Using masking tape (the wide one is Frog's Tape and the thin one is regular painter's tape) to create a background is fun, especially if you're not lining things up with a T-square.
I've started with a white mat board, utilizing masking tape in a criss-cross pattern and painting a quinacridone pink wash over top. Before the wash dried, I blotted it lightly with a cloth to create some variegation in the surface.
When the tape is lifted after the paint has dried, the white of the board remains.
And again a new look. You'll note that when you're pulling off the masking tape, you'll have better success if you pull it off at a 90 degree angle as below.
And it just gets richer and more complex the more layers are added.
The final layer is set up and left to dry,
Here's to getting your mask on in the studio!