In order to achieve white areas on a watercolor substrate, you need to use masking fluid or liquid frisket. When you brush on the fluid, it will seal off or “mask” the areas where you don’t wish for the paint to go. I’ve personally had great success with the one by Winsor Newton, and it was used in the following demo. Lightly sketch your design on watercolor paper and apply the frisket to the areas you want to mask off. It will dry to a light yellowish hue.
Next, start brushing on your watercolors in several different shades, to add depth and interest. You’ll notice that the paint will bead up on the areas where you applied the masking fluid. Allow your paper to dry thoroughly.
Slowly peel off the masking fluid, being careful not to tear the watercolor paper. You could leave these areas white, but I chose to add a lighter shade of green to the leaf’s veins. See how the masked off areas allow the lighter shades to pop? Even if you had first painted these areas on the substrate, chances are that additional watercolors would have bled into it. This is a surefire way to get those crisp lines and shapes, that are otherwise hard to achieve with watercolors.
After all the painted areas on the leaves were done, I finished the piece by adding detail with Micron pens. A fun technique to try, especially when wanting to pull white areas out of randomly applied watercolor washes. Fear of muddy effects? Don’t risk it…use frisket!