Yes, some of the colors do crack after they have dried, but this is normal. Cobalt Green Turquoise PG50 is one of them. Dominic, one of my YouTube followers suggested that I add 2-3 drops of vegetable glycerin to the paint before it dries in the wells. You can also use honey in the same quantity, but unfortunately honey might attract ants. Using cracked paint will not streak your paintings either, as you will be mixing the color evenly before you apply it to the paper.