I have struggled with darks. I've been warned against out-of-the-tube black. I have been mixing my own, from ultramarine and burnt umber. Nice, but not so predictable. I read about Gamblin's Chromatic Black in the Blick catalog and bought a tube a couple of weeks ago. It's mixed from Quinacridone Red and Pthalo Emerald green. It is much more transparent than regular black and grays mixes nicely instead of making them flat and dull. Predictably, consistantly. It's my new go-to.