Lake pigments

Jo Kirby, of the National Gallery, London, defines a lake pigment as one ‘made by the precipitation of an organic dyestuff onto an inert, insoluble, inorganic substrate’. To avoid toxicity most of my lake pigments are made with alum (aluminium sulphate) and soda ash (sodium carbonate). The dye is extracted from the plants by simmering or steeping. After filtering, alum is added, followed by soda ash, and the resulting pigment washed, filtered and dried. I have a particular interest in making pigments form plants considered invasive, overly abundant, or otherwise problematic such as bracken, dock and ragwort.