Three of the many ways you might keep your whites.....well, white.....in watercolor are:
- Use a colored pencil wax resist
- Keep the colors “corralled” with a water “lasso”.To see more about this technique please see this blog post: http://lyneartblog.blogspot.com/2019/10/watercolor-play-day-at-library.html
- Use a fluid mask to hold back the watercolors. To see more about this technique please see this blog post: http://lyneartblog.blogspot.com/2015/06/winterglow-or-pouring-it-on.html
For the first technique, a colored pencil wax resist, you are using the wax in a colored pencil to keep your watercolor from soaking into the watercolor paper where ever you have drawn your line. Use of colored pencil, especially without erasing it, is not really an American Watercolor Society accepted practice.....but if following a juried show rule is not an issue.....I've found it does the job quite nicely.
This is a bitty sample of how it works:
First I drew a small circle using a white colored pencil, and inside of the circle I drew the letter A. I'm not including a photo of this step.....'cause you wouldn't actually see anything!
At the bottom of this bitty test sheet you can see the actual circle containing the watercolor paint. I brushed inside the white wax colored pencil circle with water..... then floated in deep blues and a yellow and let them mingle and then dry.
After the watercolor was dry, I took a brush with water only.....and brushed the dried watercolor off of the letter drawn with the wax colored pencil. This revealed the white wax colored pencil “A”. It's not a perfect brite white.....but it should blend in with the rest of your painting. It's especially useful when you just need a bit of white detailing.
The little flower study above has a pink colored pencil outline and the white petals of the flower are a mixture of the water lasso effect and a bit of colored pencil on the tips.
I did a watercolor of a building that shows off a bit about this technique when used in a painting, in this blog post: http://lyneartblog.blogspot.com/2015/08/window-studyor-new-coat-of-paint.html
I recommend a book Paint Radiant Realism by Sueellen Ross for more about this technique.