Natural Black Dye: How to Get Black and Charcoal with Plants

A true natural black dye is one of the hardest colors to get with plants. There is no single "black plant." Instead, dyers combine tannin with iron, and often build on a dark indigo base. This guide explains how it works and gives four recipes with % WOF, from soft charcoal to deep black.

How natural black works

When tannin meets iron, the two form dark iron-tannin compounds. This is the same reaction that makes oak gall ink. On fabric, the tannin goes in first, then iron turns it grey or black in seconds.

The tannin you choose sets the undertone:

• Oak galls and sumac give cool blue-greys and blue-blacks.
• Pomegranate gives olive greys and green-blacks.
• Walnut gives warm brown-greys and brown-blacks.
• Acorn gives neutral to warm greys.

Tannin and iron alone often look slightly brown or blue. A dark blue indigo base under the black cancels that cast and makes the result look neutral. An experimental study of early Irish and Scottish blacks found that a woad base under oak galls and iron gave the richest blacks, with no brown hue and good lightfastness (Stillwell-Hasan, 2025).

Ingredients for black and charcoal

Ingredient	Role	Rate per cycle
White or green oak gall powder	Strongest tannin, cool black	15–20% WOF
Sumac leaf powder	Tannin, cool grey	30–40% WOF
Pomegranate peel powder	Tannin and yellow dye, olive-black	30% WOF
Acorn tannin extract	Tannin extract, neutral grey	8–10% WOF
Black walnut hull powder	Brown dye with tannin, no mordant needed	25–50% WOF
Ferrous sulfate (iron)	Turns tannin grey and black	Cotton/linen 1–2% WOF per dip (never above 4%); wool/silk 1% or less
Indigo	Dark blue base	Medium to dark vat, 4–8 g/L

Use the WOF calculator to work out grams for your fabric.

Before you start

• Scour well. Cotton and linen need a hot soda ash scour. See how to prepare fabric for dyeing.
• Pick your fiber. Cotton and linen take black best and tolerate iron well. Wool and silk can go black too, but iron can make them harsh, so use less.
• Use two containers. One for tannin, one for iron. Never let iron get into your other dye pots.
• Wear gloves. Iron stains skin and surfaces.

Recipe 1: Charcoal to black on cotton or linen (oak galls + iron)

For 100 g of scoured cotton or linen, for example our undyed cotton-linen fabric.

• 15–20 g white oak gall powder or green oak gall powder (15–20% WOF)
• 1–2 g ferrous sulfate (1–2% WOF) per dip

1. Simmer the gall powder in about 1 litre (1 quart) of water for 1 hour. Strain through fine cloth.
2. Add the tannin liquid to 3–4 litres (about 1 US gallon) of warm water.
3. Add the wet fabric. Hold at about 70 °C (160 °F) for 1 hour, or soak overnight at room temperature. Stir often.
4. Dissolve the iron in a cup of hot water. Stir it into a second container with 3–4 litres of cold water.
5. Squeeze the fabric. Do not rinse. Put it into the iron bath and keep it moving for 15–30 minutes. It turns grey at once.
6. Lift it out and let it air for 15 minutes. Rinse.
7. Repeat steps 3–6 for a darker shade. One cycle gives mid grey, two give charcoal, three give near-black.
8. Wash in pH-neutral soap and rinse until the water runs clear.

Tip: Reuse the iron bath for the next cycle. Add a little fresh iron only if the color stops developing.

Recipe 2: Deep black on an indigo base

This is the most reliable route to a true, neutral black. It works on cotton, linen, wool and silk.

1. Dye medium-dark blue. Use a natural indigo vat at 4–8 g/L, made with fructose. Give several dips, letting each oxidize fully. See the indigo vat guide.
2. Rinse and dry. Let the indigo cure for a day if you can.
3. Tannin bath. Cotton and linen: oak gall powder at 15–20% WOF. Wool and silk: oak gall powder at 10–15% WOF or sumac leaf powder at 30% WOF, at 60–70 °C (140–160 °F).
4. Iron bath. Cotton and linen: 1–2% WOF. Wool and silk: 0.5–1% WOF, warm, not hot.
5. Repeat tannin and iron once more if needed. Rinse and wash.

The darker the blue base, the fewer tannin-iron cycles you need.

Recipe 3: Brown-black on wool with walnut

Walnut hulls contain their own tannin and dye fiber without a mordant. Iron pushes them toward black-brown.

• 100 g wool, for example our undyed merino wool top
• 50 g black walnut hull powder (50% WOF)
• 0.5–1 g ferrous sulfate (0.5–1% WOF)

1. Simmer the walnut powder for about 2 hours. Let it cool overnight. The color deepens with air.
2. Strain well. Walnut leaves a lot of sediment.
3. Add the wet wool. Heat slowly to 80 °C (176 °F) and hold for 1 hour. Cool in the bath.
4. Dissolve the iron in hot water. Add it to a bath of warm water, no hotter than 55 °C (130 °F).
5. Dip the wool for 10–20 minutes. Lift out when you like the color. Rinse and wash gently.

For a deeper, cooler black, dye the wool medium blue in indigo first. More walnut recipes: black walnut dye guide.

Recipe 4: Olive-black and cool grey with pomegranate or sumac

For 100 g of tannin-friendly fabric:

• Olive-black: 30 g pomegranate peel powder (30% WOF), then iron at 2% WOF on cotton (1% on wool).
• Cool grey: 30–40 g sumac leaf powder, then iron at 2% WOF.
• Neutral grey: 8–10 g acorn tannin extract, then iron at 2% WOF.

Follow the same tannin-then-iron steps as Recipe 1. Pomegranate over light indigo gives deep bottle-green and green-black. See the pomegranate dye guide.

Layering tips for richer blacks

• Several light cycles beat one heavy bath. They give more even color and less fiber damage.
• If a black looks too blue, add a walnut or pomegranate cycle. If it looks too brown, add indigo.
• Madder plus iron gives plum and aubergine. Over dark indigo, this reads as a warm near-black. See madder purples and mauves.
• Always let fabric air between tannin and iron cycles.

Protect your fiber

Iron is acidic and can slowly weaken both cellulose and protein fibers. Conservation research on black-dyed historic cotton links soluble iron to loss of strength and color over time (Redzic et al., 2024). To reduce the risk:

• Stay within the iron rates above. More iron does not mean more black.
• Rinse and wash until no more color or iron comes out.
• Use the indigo base so you need less iron.

Read more in our iron mordant guide, and find all the ingredients in our natural black and grey dyes collection.

Troubleshooting

• Brown instead of black: too little tannin or a warm tannin like walnut. Use oak galls and add an indigo base.
• Mid grey, not black: do more tannin-iron cycles rather than adding more iron.
• Blotchy or streaky: fabric was not scoured or pre-wetted, or the iron was poured onto the fabric. Always dissolve iron first and keep fabric moving.
• Rusty orange spots: undissolved iron crystals. Dissolve in hot water and strain.
• Color rubs off: loose surface particles. Rinse and wash well.
• Wool feels harsh: too much iron or too much heat. Use 1% WOF or less and keep the bath warm, not hot.

Frequently asked questions

Is there a single plant that dyes fabric black?

Not really. Natural black almost always comes from tannin combined with iron, often layered over a dark blue indigo base. Walnut can give very dark brown, but on its own it rarely reads as true black.

Will a tannin and iron black fade?

Iron-tannin blacks are fairly lightfast, but they can drift toward brown or grey over time. A dark indigo base under the tannin and iron gives a deeper, more stable black.

Can I dye wool black with natural dyes?

Yes, but be gentle. Keep iron at 1% WOF or less per dip, keep the iron bath warm rather than hot, and build depth with an indigo base and several light cycles instead of one strong iron bath.

Why does my black rub off on my hands?

Loose iron-tannin particles are sitting on the surface. Rinse until the water runs clear, then wash with pH-neutral soap. Next time, squeeze out excess tannin before the iron dip and add iron solution slowly.

How many cycles do I need for black?

On cotton and linen, one tannin and iron cycle usually gives mid grey, two give charcoal and three give near-black. On an indigo base, one or two cycles are often enough.

Sources and further reading

• Stillwell-Hasan, A. (2025). Searching for Dubh: Experiments in Black Dyes Pre 15th Century in Ireland and Scotland. EXARC Journal 2025/1.
• Redzic, A. et al. (2024). Experimental Treatment for Black-dyed Cotton Textiles Using Japanese Adhesives Funori and Nikawa. Hozon Kagaku 63, 15–30.
• Botanical Colors. How to make your own signature black natural dye.
• Maiwa. Tannin and iron scarf kit.
• Wild Colours. Pomegranate.

Related: Aleppo oak galls tannin guide · Purple and brown shades from plant dyes · Indigo vat guide