Aleppo Oak Galls (Quercus infectoria): Complete Tannin Guide for Natural Dyeing

Aleppo oak galls (Quercus infectoria) are one of the richest natural sources of tannin used in traditional crafts. In natural dyeing they are used as a tannin treatment that helps plant fibers such as cotton and linen take color more evenly and more deeply. With iron, they turn fabric grey, charcoal and near-black. Oak galls are also the classic base for iron gall ink and have a long history in leather tanning.

This guide answers the questions we hear most often: what oak galls are, how to use them, how much to use, what colors to expect and what to watch out for.

What are oak galls?

Oak galls are round growths that form on oak twigs when a small gall wasp lays its eggs in the tree. The tree reacts by building a protective, tannin-rich shell around the larva. Galls collected before the insect leaves are called green galls: they are small, heavy, dark and highest in tannin. White galls are collected after the insect has left through a small hole; they are larger, lighter in weight and color, and slightly lower in tannin.

The name Quercus is often linked to old Celtic words for "beautiful tree", and oak galls have been used for ink, dyeing and tanning across the Middle East and Anatolia for centuries.

Our oak galls from Turkey

themazi is a family company that has worked with oak galls in Turkey since the 1950s. We collect galls every year in August and September, sort them by color into green and white, and remove damaged galls by hand. We offer them in two forms:

• White oak galls (whole) and white oak gall powder: a clear tannin that adds little color, ideal under bright dyes.
• Green oak galls (whole) and green oak gall powder: the strongest tannin, ideal for deep greys, blacks and ink.

Whole galls give you full control and keep best in storage; grind only what you need. Powder disperses and extracts faster and makes repeatable dosing easier. The chemistry is the same; only the workflow differs.

What can you use oak galls for?

Natural dyeing

• As a tannin treatment for cotton, linen and other plant fibers before mordanting with alum.
• As a base for iron greys and blacks.
• In eco printing, where tannin-treated fabric gives sharper, darker leaf prints.

Ink making

Oak galls combined with iron sulphate and gum arabic make traditional iron gall ink. See our oak gall ink recipe.

Leather work

Tannins are central to traditional leather tanning, and oak galls are one of the classic tannin sources.

Which fibers benefit most?

Cellulose fibers such as cotton, linen, hemp, ramie and viscose need extra help to hold plant dyes, and a tannin treatment is one of the most effective tools. Protein fibers such as wool and silk dye well with alum alone, but oak galls can still be used, especially for iron greys and blacks.

How much to use (WOF)

WOF means weight of fiber: the dry weight of your fabric or yarn.

• Tannin treatment for cotton and linen: 5–12% WOF (5–7% for a light treatment, 8–12% for deeper results).
• Oak galls as a beige or tan dye: 10–25% WOF.
• Iron for greys and blacks: 1–3% WOF, starting at 1%.

Example: for 500 g of dry fabric, use 50 g of oak galls (10% WOF) and 5 g of iron (1% WOF).

Step by step: tannin treatment for cotton and linen

1. Scour first. Wash the fabric with soda ash to remove oils, starch and finishes. Skipping this step is the most common reason for weak or patchy color. Our guide to preparing fabric for natural dyeing explains how.
2. Make the tannin bath. Fill a pot with enough water for the fabric to move freely, add the oak galls (5–12% WOF) and heat gently to 50–70 °C (122–158 °F).
3. Treat the fabric. Add the wet fabric and hold for 45–90 minutes, stirring now and then. For deeper results, leave it in the cooling bath overnight.
4. Continue with alum. Rinse lightly and mordant with alum. Our guide to mordanting cotton and linen covers the full method, or use the cellulose mordant studio kit.

Tannin-treated fabric can be dried and stored, then mordanted and dyed later.

Using oak galls on wool and silk

• Keep the temperature at 40–60 °C (104–140 °F).
• Avoid sudden temperature changes and heavy stirring, which can felt wool.
• Start at 5–8% WOF and test a small sample first.

Oak galls and iron: greys and blacks

Oak galls react strongly with iron, shifting color from grey to charcoal to near-black depending on the fiber, strength and time. The safest method is a tannin bath first (8–12% WOF), then a short dip of 1–5 minutes in a weak iron (ferrous sulphate) bath at 1–3% WOF, followed by a thorough rinse. Too much iron can weaken fibers over time, especially wool and silk, so always start low. For more dark shades, see our natural brown and black dyes.

What colors to expect

• Warm beige and tan from oak galls alone.
• Greys to near-black with iron.
• Deeper, more even color from other dyes when oak galls are used as a tannin treatment.

Results vary with water hardness, fabric preparation and technique, so always test a swatch.

Storage and safety

• Keep oak galls sealed in a cool, dry place away from humidity and sunlight. Powder is more sensitive to moisture than whole galls.
• Avoid inhaling fine powder and wear a mask when grinding.
• Use dedicated dye pots and tools, never kitchen equipment.

Troubleshooting

• Weak color on cotton or linen: scour again and increase tannin to 8–12% WOF.
• Patchy color: use more water and stir more often so the fabric can move freely.
• Too dark with iron: reduce iron to 1% WOF and shorten the dip.

Frequently asked questions

Is oak gall a dye or a mordant?

Oak gall is a tannin. It prepares plant fibers for a metal mordant such as alum, and it can also act as a beige dye or, with iron, as a grey and black dye.

What is the difference between green and white oak galls?

Green galls are collected before the insect leaves and contain more tannin. White galls are collected later, are lighter in color and give a cleaner base under bright dyes.

Can I buy oak galls in bulk?

Yes. Whole and powdered oak galls are available in 1, 5 and 25 kg bags. See our wholesale natural dyes page.

Related: Shop all natural tannins · Guide to mordants · Alum mordant guide · Undyed fabric for dyeing