A. Good question. I have a few of those around the studio myself. You can’t really use them for large areas or for loading up your brush. You can salvage a little color, however, by cutting the tubes in half, moistening your brush with a lot of water, and swishing it around in the dry watercolor in the tube. You can also try to dissolve the hard paint in water by scraping out the tube and letting the paint soak in one of the wells on your palette.