Making pigment powder from plants involves extracting color from botanical material, then converting that liquid dye into a solid powder through a simple chemical reaction. The technique, called “lake pigment” making, requires only three core ingredients beyond the plant itself: aluminum sulfate, soda ash, and water. The entire process takes about two days from start to finish, with most of that time spent waiting for things to dry.
Choosing the Right Plants
Not every colorful plant produces a pigment worth keeping. The best candidates are traditional dye plants that have been used for centuries specifically because their color holds up over time. Madder root produces rich reds and corals. Marigold flowers yield reliable golds. Dyer’s coreopsis gives vibrant yellows and oranges. Japanese indigo creates deep blues, though it requires a slightly different extraction process than most plants. Dyer’s chamomile offers a subtle, warm yellow.
Fresh flowers and leaves work, but dried plant material is easier to measure consistently and stores well until you’re ready. You’ll want at least 20 grams of dried material to produce a usable amount of pigment. More is better, since the yield from plants is modest compared to synthetic dyes.
One thing to keep in mind: plant-based pigments are organic compounds, and organic pigments are more susceptible to fading from ultraviolet light and weathering than mineral pigments. Madder and indigo are among the most lightfast botanical options. If you plan to use your pigment in artwork exposed to sunlight, stick with those or accept that some fading will happen over months to years.
Extracting the Dye
Start by simmering your dried plant material in distilled water. Use roughly 200 milliliters of water for every 10 grams of plant material. Keep the temperature below a full boil, somewhere around 80°C (175°F), and let it simmer for 30 to 60 minutes until the water is deeply colored. Some plants like madder release more color at lower temperatures, closer to 65°C (150°F), so a gentle approach works best as a default.
Once the color is extracted, strain the liquid through a coffee filter placed in a funnel or sieve. You want a clean liquid free of any plant bits. Squeeze or press the filter to get as much dye out as possible. Discard the spent plant material or compost it.
The pH of your dye liquid affects the final color. Acidic conditions tend to push colors toward warmer, redder tones, while alkaline conditions shift them toward cooler or darker shades. You can experiment with adding a small amount of vinegar (acid) or soda ash (alkali) to your extraction water to nudge the hue before moving to the next step.
Precipitating the Pigment
This is the core chemistry that transforms a liquid dye into a solid powder. You need two chemicals: aluminum sulfate (alum) and sodium carbonate (soda ash, also sold as washing soda). Both are inexpensive and available at grocery stores or online. Baking soda can substitute for soda ash in a pinch, though soda ash is more effective.
Here’s the process, using 30 grams of dried madder root as a working example:
- Measure the alum. Use 60% of the weight of your starting plant material. For 30 grams of madder, that’s 18 grams of aluminum sulfate.
- Measure the soda ash. Use half the weight of the alum. For 18 grams of alum, that’s 9 grams of soda ash.
- Dissolve the alum. Reheat your strained dye liquid to around 50–80°C (110–175°F) and pour it into a jar at least twice the volume of the liquid. Add the alum directly and stir until completely dissolved.
- Dissolve the soda ash separately. Mix the soda ash into a small amount of hot distilled water in its own container, about 200 milliliters per 10 grams.
- Combine slowly. Pour the soda ash solution into the dye-and-alum mixture gradually. It will fizz and bubble. This is carbon dioxide releasing as the acidic alum reacts with the alkaline soda ash, which is normal and expected. Use a container with plenty of headroom.
What’s happening chemically is straightforward: the aluminum forms an insoluble compound that traps the dye molecules, pulling them out of the liquid and into a solid form. This solid is your lake pigment.
Collecting and Washing
After combining everything, you can either let the mixture sit overnight (the pigment will settle to the bottom as a layer of opaque sludge) or pour it immediately through a coffee filter to collect the solids. Letting it settle first makes filtering faster, since you can carefully pour off most of the clear liquid on top before filtering the rest.
The wet pigment collected in the filter needs to be washed. This removes leftover mineral salts that would crystallize as the pigment dries, and clears out any remaining plant residue that could cause mold or spoilage. Drop the filter with its pigment into a jar of clean distilled water, about four times the volume of the pigment. Swish it gently, let it settle, then filter again. Repeat this rinse a second time for a total of two washes.
Drying and Grinding
Spread the wet pigment paste thinly on a glass plate, ceramic tile, or piece of parchment paper. Let it air dry in a warm, well-ventilated area. This can take one to three days depending on humidity and how thick the layer is. If you want to speed things up, you can place it in an oven set to around 60°C (140°F) for several hours. Avoid going above 100°C, as excessive heat can alter or dull some plant-based colors.
Once fully dry, the pigment will be a hard, crumbly cake. Break it up and grind it into a fine powder using a mortar and pestle. A ceramic or agate mortar and pestle works well and won’t contaminate the pigment. Glass mullers, the traditional artist’s tool for grinding pigment on a flat slab, produce an especially fine and even powder. Whatever you use, the goal is a consistency like flour or fine talc. Coarser particles produce gritty paint, so grind thoroughly and sieve if needed.
If your dried pigment is still slightly flexible or gummy rather than brittle, it likely retained moisture. Dry it longer before attempting to grind.
Turning Pigment Into Paint
Pigment powder on its own is just colored dust. To make it usable, you mix it with a binder that holds the particles together and adheres them to a surface. The binder you choose determines the type of paint you end up with.
- Gum arabic dissolved in water creates watercolor or gouache. This is the simplest option and works beautifully with botanical pigments. Mix a small amount of gum arabic solution into your powder on a glass slab until it forms a smooth paste.
- Egg yolk produces tempera paint, a technique older than oil painting. Separate a yolk, puncture the membrane, and mix the yolk directly with pigment. Tempera dries fast and produces a matte, luminous finish.
- Walnut oil or linseed oil creates oil paint. Slowly incorporate oil into pigment on a glass slab using a muller or palette knife until you reach a buttery consistency. Oil paints take days to dry but produce rich, workable color.
- Casein, derived from milk protein, makes a durable, fast-drying, water-soluble paint that has been used since ancient times.
- Egg white (glair) produces a translucent paint historically used in manuscript illumination.
Start with small batches when experimenting. Different pigments absorb different amounts of binder, so ratios vary. Add binder gradually until the mixture is smooth and paintable.
Safety Considerations
The materials used in basic lake pigment making, specifically aluminum sulfate and soda ash, are low-toxicity household chemicals. Aluminum sulfate is used in water purification and pickling. Soda ash is a common laundry additive. Neither poses serious health risks at the quantities involved, though you should avoid inhaling dry powder of any kind and work in a ventilated space.
Where pigment making gets genuinely dangerous is with heavy metal mordants. Historically, pigments were made using compounds of lead, cadmium, cobalt, chromium, and mercury to achieve bright, stable colors. These metals accumulate in the body, damage organs, and many are known carcinogens. Avoid any recipe calling for copper sulfate, potassium dichromate, tin chloride, or lead acetate. Aluminum sulfate is the only mordant you need for safe home pigment production, and it produces excellent results.
Storing Your Pigment
Dry pigment powder keeps indefinitely when stored properly. Use small glass jars with tight lids, and keep them away from direct sunlight and moisture. Label each jar with the plant source, the date, and any notes about the process, since subtle color differences between batches are common and you’ll want to remember what worked. The pigment itself won’t spoil, but if it was insufficiently washed or not fully dried before storage, residual plant matter can grow mold. If your stored pigment develops an off smell or visible mold, discard it and wash more thoroughly next time.