Pbo Drawing Gum is ideal for preserving white areas on your paper for watercolour and airbrush. It is a removable grey liquid frisket that is water soluble when wet, but dries waterproof. Excellent for fine detail work.

Apply with a brush (not your best one), a Color Shaper, Incredible Nib, or cotton bud. Removes easily from most papers with a finger, rubber cement pick-up, or soft eraser. As with all liquid masks, be sure not to leave on your painting too long, and be sure to do a test on any surface that you havent used it on previously.