Artist's tube watercolors. The pigments in these are very finely-ground, even moreso than acrylic paints, and can be used for washes and special effects. A watercolor wash can be applied, and after drying, areas can be removed with a clean brush and water to create a spotted or patched effect. Watercolors must be sealed with a a couple of light sealer coats after application, or subsequent painting will cause the watercolors to run.