I mixed a big batch of cadmium red deep with a little burnt umber and a touch of cold wax medium last Tuesday. Laid it down in a broad band across the bottom third of a 180 x 140. Looked right. Earthy but alive. Yesterday I walked in and it had gone brown. Flat and dead. Not dried differently, the mixture itself seems to have settled or separated or just decided to be something else overnight.

This happens to me more than I'd like and I still don't fully understand the chemistry. The pigment particles are heavy, I know that. Maybe the cold wax lets them migrate in ways I'm not accounting for. Or maybe I'm just not mixing thoroughly enough. But I stir it for a good five minutes, scrape and fold.

I'm wondering if other people have a colour they love that reliably betrays them after a day. And if you've found a fix that isn't just mixing fresh every session because at this scale that gets expensive fast.