Making a Lake Pigment from Plant Dye — Precipitating Soluble Colour onto an Insoluble Substrate

Place 50-100 g of dye material in a pot with 1 litre of water. For a classic madder lake, use dried, chopped madder root. For other lakes, use any strong plant dye source: dried hibiscus calyces (pink-red), onion skins (golden-yellow), black hollyhock flowers (purple), or logwood chips (violet). Simmer at 70-80°C for 30-45 minutes to extract the dye. The liquid should be intensely coloured — much stronger than a normal dye bath. Strain out the plant material through a fine mesh strainer. The clear, deeply coloured liquid is your dye extract.

While the dye extract is still hot (70-80°C), dissolve 30-50 g of alum (potassium aluminium sulfate, KAl(SO₄)₂) in the liquid. Stir until fully dissolved. The alum provides the aluminium ions that will form the insoluble substrate. The liquid will remain clear and deeply coloured. If the colour shifts slightly (some dyes are pH-sensitive), this is normal — the final pigment colour is determined after precipitation.

Dissolve 15-25 g of sodium carbonate (soda ash) in 100 ml of warm water. Slowly add this alkali solution to the hot dye-alum mixture, stirring gently. The liquid will immediately begin to foam and a coloured precipitate will form — this is alumina hydrate (Al(OH)₃) carrying the dye molecules with it. Add the alkali solution gradually in small portions, stirring between additions. The foaming is CO₂ gas released by the reaction. Stop adding alkali when no more precipitate forms and the liquid above the precipitate is nearly clear.

Let the precipitate settle for 30 minutes. Pour off the clear liquid above. Pour the coloured precipitate through a fine-weave cloth (muslin or cotton) stretched over a jar. Let the liquid drain — the coloured mass on the cloth is your lake pigment. Wash the precipitate by pouring clean water through it 2-3 times to remove residual alum and alkali salts — unwashed lake pigments can bloom or effloresce over time. Squeeze the cloth gently to remove excess water.

Spread the wet lake pigment in a thin layer on a clean glass or ceramic surface and let it dry completely — 1-3 days in a warm, dry location. The dried lake will be a hard, coloured cake. Break it up and grind to a fine powder with a mortar and pestle or on a glass slab with a glass muller. Madder lake produces a beautiful rose-pink to deep crimson, depending on the madder variety and alum ratio. Store in a sealed glass jar away from light. This lake pigment is ready to mix with any binder: egg yolk for tempera, gum arabic for watercolour, linseed oil for oil paint.