Now I know why ultramarine, ground from lapis lazuli, was so expensive. Purify and purify and purify. So we had it more easy, starting from ready-pulverised granules, using malachite. The finer you grind it the paler it goes. Our holy grail was trying to get something darker. We played with recipes, adding egg yolk and so on. Did we succeed? Maybe not. Was it blue? Was it green? But it was fun. And dried plants like weld can be wetted, squeezed and mixed with alum mordant. The resulting frothy foam is captured and dried for a lovely yellow. We learned that you want the fine ground remains from rocks, so you sluice off the water that takes away the impurities. But let earthy soils sink and keep the stained water for the browns. Toni took our efforts and ground them further. Proud of what we helped produce. You have to do a workshop with Toni to learn the secrets!