Tannin Mordant Guide: Natural Tannins for Dyeing Compared
A tannin mordant is the first step to strong, lasting natural dye color on cotton and linen. Tannins are plant compounds that cling to cellulose fibers and also grab metal mordants such as alum and iron. This guide compares the natural tannins for dyeing that we stock: white and green oak galls, sumac leaf, red pine bark extract, acorn tannin extract and pomegranate peel. You will learn which ones stay clear, which ones add color, and how much to use.
If you want a deep dive into one tannin, read our Aleppo oak galls tannin guide. This article focuses on choosing between tannins.
What a tannin mordant does
Alum bonds well to wool and silk, but poorly to cellulose. Cotton and linen need a "bridge." Tannin is that bridge. It soaks into the fiber, then alum binds to the tannin-fiber complex. The dye then binds to the alum.
The standard order for cellulose is:
- Scour the fabric (see how to prepare fiber and fabric).
- Tannin bath.
- Alum bath, 12–15% WOF, with soda ash 1.5–2% WOF.
- Dye.
The full method is in our guide to mordanting cotton and linen. If you prefer pre-measured materials, the cellulose mordant kit has everything in one box.
Tannin is also a color in its own right. With iron it turns grey or black. This is the same chemistry as iron gall ink. See our natural black dye guide.
Hydrolysable vs condensed tannins
Chemists sort tannins into two main families. The difference matters in the dye pot.
Hydrolysable tannins
These are built from gallic acid or ellagic acid units joined to a sugar. They split apart (hydrolyse) in hot water, acid or alkali. There are two sub-groups:
- Gallotannins: oak galls and sumac leaf. Oak galls are very rich, often cited at about 75% hydrolysable tannins (Degano et al., 2019).
- Ellagitannins: pomegranate peel, acorn and acorn cup (valonia) tannins, and myrobalan.
In practice, hydrolysable tannins are paler. Gallotannins are the clearest of all. With iron they give cool blue-greys and blue-blacks.
Condensed tannins
These are chains of flavonoid units joined by strong carbon-carbon bonds. They are also called proanthocyanidins. Pine bark, quebracho, cutch and grape seed are typical sources.
Condensed tannins usually add a pink-tan to red-brown tint. This tint can deepen with air and light over time. With iron they tend toward warmer brown-greys rather than blue-black.
Tip: Use a hydrolysable, clear tannin under bright colors. Use a condensed tannin when you want warm, earthy shades or a soft base tint.
Natural tannins compared
Rates are % WOF (weight of dry fiber) for mordanting cotton or linen. Use our WOF calculator to turn these into grams.
| Tannin | Type | Tint on cotton | With iron | Rate for cellulose |
|---|---|---|---|---|
| White oak galls | Hydrolysable (gallotannin) | Almost clear, faint cream | Blue-grey to blue-black | 8–15%, start at 10% |
| Green oak galls | Hydrolysable (gallotannin) | Pale cream | Grey to black | 8–15%, start at 10% |
| Sumac leaf powder | Hydrolysable (gallotannin) | Pale cream to soft yellow | Cool grey | 20–40%, start at 30% |
| Pomegranate peel powder | Hydrolysable (ellagitannin) | Yellow to green-gold | Olive to dark grey | 20–30%, start at 30% |
| Acorn tannin extract | Mostly hydrolysable | Beige to light tan | Grey to charcoal | 5–10% (extract), start at 8% |
| Red pine bark extract | Condensed | Pink-tan to soft red-brown | Warm brown-grey | 5–15% (extract), start at 10% |
The ranges reflect how strong each material is. Oak galls are very concentrated. Leaves and peels contain less tannin, so you need more of them.
White oak galls
White oak galls are the classic clear tannin. Choose them under yellows, pinks and light blues, where any tint would muddy the color. White oak gall powder saves you the work of crushing whole galls.
Green oak galls
Green oak galls are harvested earlier and are prized for ink. They work the same way as white galls in the dye pot. The powdered form is green oak gall powder. They are a good choice for greys, blacks and oak gall ink.
Sumac leaf
Sumac leaf powder is a gentle, budget-friendly gallotannin. It is less concentrated than galls. Wild Colours suggests about 40 g dry sumac leaves per 100 g cotton (40% WOF). Start at 30% and adjust.
Pomegranate peel
Pomegranate peel powder is a tannin and a yellow dye in one. The rind contains about 19–26% tannin (Wild Colours). Botanical Colors uses 30% WOF of peels as a tannin mordant. Use it when a yellow or green-gold base will help your final color, for example under indigo for greens. See the pomegranate dye guide.
Acorn tannin extract
Acorn tannin extract comes from oak acorns and cups. Oak acorn cup (valonia) tannin is an ellagitannin, a hydrolysable tannin (Liu et al., 2021). It gives a soft beige tint and good greys with iron.
Red pine bark extract
Red pine bark tannin extract is a condensed tannin. It leaves a warm pink-tan base. That warmth flatters madder reds, rusts and browns. Avoid it under clear yellows or icy blues.
Extracts vs raw tannins
Raw materials (whole galls, leaf and peel powders) and extracts both work. They differ in convenience.
- Extracts are concentrated and dissolve almost fully. You use less, there is little sediment, and results are more even. Typical rates are 5–10% WOF.
- Raw materials must be simmered and strained. They are often cheaper per kilo and can carry extra color. Rates run from about 10% for oak galls to 20–40% for leaves and peels.
For comparison, Maiwa recommends gallnut extract at 6–8% WOF. Wild Colours uses about 6% gallnut extract or tannic acid. Botanical Colors uses 5–10% of its tannin extracts.
Tip: Fine powders can leave dark specks on fabric. Always strain raw tannin baths through a fine cloth.
How to make a tannin bath for cotton and linen
This method is for 100 g of scoured, dry fabric. Scale with the WOF calculator.
- Weigh the dry fabric. Weigh your tannin: for example 10 g oak gall powder (10%) or 8 g acorn extract (8%).
- Prepare the tannin. Dissolve an extract in a cup of boiling water. For a raw powder, simmer it in about 1 litre (1 quart) of water for 1 hour, then strain.
- Fill the pot with enough warm water for the fabric to move freely, about 3–4 litres (about 1 US gallon). Stir in the tannin liquid.
- Add the wet fabric. Pre-wet it for at least 1 hour so it absorbs evenly.
- Heat or soak. Hold at about 70 °C (160 °F) for 1 hour, or soak at room temperature from 2 hours to overnight. Stir often in the first 15 minutes.
- Squeeze, do not rinse. Go straight to the alum bath (see our alum mordant guide), using alum at 12–15% WOF and soda ash at 1.5–2% WOF.
Tip: Keep the tannin bath. Cover and label it. You can reuse it for a second, lighter batch or top it up with fresh tannin.
Which tannin should you choose?
- Bright yellows, pinks, light blues: white oak galls.
- Warm reds, rusts and browns: red pine bark extract, alone or mixed with oak gall.
- Greens and golds: pomegranate peel.
- Greys and blacks with iron: oak galls, sumac or acorn extract.
- Large batches on a budget: sumac leaf.
Browse the full range in our natural tannins collection.
Troubleshooting
- Blotchy or streaky fabric: the fabric was not fully scoured or pre-wetted, the pot was too crowded, or tannin particles were not strained out.
- Grey or dark spots before any iron: iron in your water or pot is reacting with the tannin. Use stainless steel or enamel pots and try filtered water.
- Colors look dull or brownish: a colored tannin (red pine, pomegranate) is showing through. Switch to white oak galls under bright colors.
- Pale color after dyeing: the fabric was rinsed after the tannin bath, or the alum step was skipped or too weak.
- Fabric feels stiff: too much tannin. Stay within the ranges above.
Frequently asked questions
Do I need a tannin mordant for wool and silk?
No. Wool and silk bond well with alum on their own. Tannin is mainly for cotton, linen and other cellulose fibers. On protein fibers you can still use tannin to deepen color or to make greys and blacks with iron.
Is tannic acid the same as oak gall tannin?
They are close relatives. Commercial tannic acid is a purified gallotannin, usually made from oak galls or sumac. Gallnut extract and tannic acid are used at about the same rate, around 5–8% WOF.
Which tannin is best if I want a pure white base?
White oak galls give the clearest result. Any tannin leaves a faint cream tint on cotton, so tie or mask areas that must stay bright white before the tannin bath.
Can I mix two tannins?
Yes. Many dyers blend a clear tannin with a colored one, for example oak gall with a little red pine bark. Keep the total near the normal rate, about 8–15% WOF for raw powders or 5–10% for extracts.
Should I rinse after the tannin bath?
No. Squeeze out the excess and go straight to the alum bath. Rinsing removes tannin that the alum needs to bind to.
Sources and further reading
- Degano, I. et al. (2019). A Mass Spectrometric Study on Tannin Degradation within Dyed Woolen Yarns. Molecules 24(12), 2318.
- Liu, J. et al. (2021). Valonea Tannin: Tyrosinase Inhibition Activity, Structural Elucidation and Insights into the Inhibition Mechanism. Molecules 26(9), 2747.
- Maiwa. Tannins: clear, yellow and red-brown.
- Botanical Colors. How to mordant cellulose fibers with tannin and alum.
- Wild Colours. Mordanting cotton with alum and tannin.
Related: Aleppo oak galls tannin guide · Mordanting cotton and linen · Mordants for natural dyeing