Processing
Step 1: Soak 150 g of madder roots (#37201) in 2 liter demineralized water. Adjust the pH of the water with acetic acid (#64550) until it has pH 4. Add 50 g of potash alum (#64100) and boil for 30 minutes, then filter off the roots.
Step 2: Dissolve 14 g of potash (#64040) in 1 L demineralized water. In order to precipitate the lake, add this solution to the madder decoction until it does not show any further foaming. Control the pH of the solution, which should be approximately 6,5 after adding the potash solution.
Step 3: After precipitation the pigment will slowly settle to the bottom. Wait at least 24 hours, then carefully pour off the liquid. The pigment slurry now has to be washed three times in order to remove soluble salts. Pour fresh demineralized water onto the wet pigment paste and stir it up. Let it settle again and pour off the washing water. Repeat this process at least twice and then filter off the pigment.
Step 4: Take the wet pigment off the filter and spread it on a plastic foil or in a flat pan for drying. Let it dry at a warm, dry place.
Note
The hue of madder lakes is determined by many factors, amonst others by the quality and origin of the roots, pH, temperature or mordant. Therefore, the result can vary each time. The hue can be slightly changed by adding for example 2 % tin chloride (#64300).
We assume no liability for the processing instructions described above. In any case, we recommend the production and evaluation of sample surfaces.
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Author: Thomas Rickert
