Just as when you work with regular watercolor, you will sometimes want to retain clean, fresh lights. And just as with traditional watercolor, you can do it by painting around the areas you wish to keep clean. You may find this approach more satisfactory than trying to use a liquid mask, as applying pencil up to the edge sometimes lifts the mask before you want to.
Here, my young friend Naomi was standing by a window in a very dark log cabin. I drew around the lightstruck areas very lightly with a graphite pencil, just to try to capture the likeness, then drew up to that line with my watercolor pencils. I allowed the shadow areas to remain dark and very simple—they were nearly featureless in that chiaroscuro lighting. I used a lot of lost-and-found edges for this painting. In areas where the lights meet the shadow, there is a sharp line; but where shadow meets shadow, the areas are allowed to blend.
You may want to plot out ahead of time the areas you plan to keep untouched by color, as in this black-and-white “map,” which helped me see where I needed to retain the pure white paper.
Instead of painting around the areas you want to save as white, you can use liquid mask with your watercolor pencils. Apply it to those areas where you want to retain the white of your paper, then carefully work the color up to the mask before washing with water. Exercise caution when using a strong scribbly effect in conjunction with liquid mask, as the bold strokes could damage the edges of the masked areas if you bang into them, lifting or altering the shapes you’ve just put down.
You may prefer a more traditional approach in small areas where you’ve decided to use mask to protect the white. Apply the liquid latex by whatever means you prefer (my most successful method is to apply it with a bamboo pen, which is easily cleaned afterward). Allow the mask to dry thoroughly, then use your watercolor pencil or crayons as though they were cakes of dry watercolor pigment. I like to use the large Lyra crayons for this, making up a small wash with clear water rubbed over the end of the crayon, then applying the wash over the mask.
However you choose to work, wet your pencil drawing as usual, allow it to dry and remove the mask just as you would with watercolors. Voilà—clean, white paper just where you wanted it. Add more small, sharp details with your watercolor pencils and then wet them judiciously.
You also could add the mask after drawing if you wanted to retain small areas as pencil, but remove it carefully because it might pull away some of the pigment with it.
The sample at left shows what happens when you paint over liquid mask with a brush (A) and what happens when you’ve scribbled carelessly over the dried mask with a pencil (B)—the white lines are broken every place the pencil tore the mask loose. For the main drawing of a cactus flower, I used liquid latex mask in a traditional way by making a pool of pigment with water and the tip of my water-soluble crayon so I could paint right over the top of the mask, allow it to dry thoroughly and then remove it.