[purifyingFlame]

This is the kind of note I was hoping for. Standard pigment codes (PR170, PR254 etc) are a good call and I wanted a proper Color Index field and this pushes it up the list. I will also take another look at the Van Dyke Brown swatch. You may be right that it reads too close to burnt sienna. Chromatopia looks like a lovely book and thanks for the Langridge pointer, glad those artisanal makers are still going.