How to dye wool with acorns , step-by-step

Acorns make warm, earthy browns and (with an iron modifier) beautiful slate/grey tones. Below is a practical, kitchen-friendly recipe plus safety tips and troubleshooting. Test on a small scrap first, natural dyes are wonderfully variable!

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Materials

• Wool yarn or wool fabric (scoured / clean). Example: 100 g sample used in recipe below.

• Acorns (caps and/or whole nuts). Fresh or dried fallen acorns both work.

• Alum (potassium aluminium sulfate) — common textile mordant.

• Cream of tartar (optional, brightens/softens the colour).

• Large stainless-steel or enamel pot (do not use pans you use for cooking, avoid aluminium).

• Wooden or stainless steel spoon, strainer, scale, thermometer (helpful).

• Gloves, apron, and good ventilation.

Safety first

• Wear gloves when handling mordants (alum) and dye baths.

• Work in a well-ventilated area.

• Don’t use aluminium pots (react with mordants).

• Do not use pots that you use for cooking food in.

• Dispose of spent dye liquid down the drain with plenty of water unless local regulations advise otherwise.

Quick recipe (for 100 g wool — use this as a template)

• Acorns: 200 gm - 400 gm (2-4 × weight of fibre)

• Water: enough to cover (about 1–2 L)

• Alum mordant: 10 g (10% weight of fibre — “10% OWF”)

• Cream of tartar: 5 g (optional, 5% OWF)

Step-by-step

1) Scour the wool

1. Fill a pot with warm (not hot) water and a little mild soap (no agitation).

2. Gently soak the wool 15–30 minutes, swish minimally to remove oils/dirt.

3. Heat the wool slowly and bring it between 60-80 °C. Do Not Boil

4. Hold the wool at this temperature for about 1 hour, then allow it to cool. Do Not Stir

5. Rinse in warm water. Handle gently to avoid felting.

2) Mordant the wool (optional with acorns)

1. Weigh your clean, dry wool (for calculating mordant). Example uses 100 g dry weight.

2. Dissolve alum (10% OWF → 10 g per 100 g fibre) and cream of tartar (5% OWF → 5 g per 100 g fibre, optional) in about 500 ml warm water.

3. Put the wool in the pot, cover with enough water so it moves freely. Add the dissolved alum mixture.

4. Gently heat to just below simmer (around 70–80 °C) and keep it there for 45–60 minutes. Do not boil or stir vigorously.

5. Turn off the heat and let it cool in the pot (30–60 minutes). Rinse gently and set aside in warm water until ready to dye.

Tip: Mordanting can also be done cold (soak overnight) if you prefer; this reduces the risk of felting.

Note:

Acorns contain high levels of tannins, and a good colour can be obtained without a mordant. I would encourage you to experiment with a wool with a mordant and some without. You can then make an informed decision about whether you are going to use a mordant.

3) Prepare the acorn dye bath

1. Soak your acorns in cold rainwater for a minimum of 2 days, or Crush or chop the acorns (cracking them open increases extraction). Include caps if you like; they carry tannins.

2. Place acorns into a pot. Cover with water (1–2 L for the amounts above).

3. Slowly bring to a simmer and maintain a low simmer for 60–90 minutes. You’ll see the water turn from pale to golden/brown.

4. Turn off the heat and steep the material in the bath for several hours or overnight (cooling with the acorns still in the bath intensifies colour).

5. Strain out solids (reserve the liquid).

4) Adjust pH (optional)

• For wool, an acid dye bath helps colour uptake. You can add a splash of white vinegar (about 1–2 tablespoons per litre) before putting in wool. This is optional if you mordanted with alum, but many dyers do it for consistency.

5) Dye the wool

1. Place the pre-mordanted, wet wool in the strained acorn dye bath.

2. Heat very gently to below a simmer (keep under ~80 °C). Leave at that temperature for 30–60 minutes.

3. Turn off the heat and allow the wool to cool in the bath slowly, ideally overnight, which deepens the colour.

4. Remove wool, rinse gently in cool water until it runs clear. Do not agitate. Hang to dry away from direct sunlight.

6) (Optional) Iron-modifying for greys/blacks

• Option A — Ferrous sulfate: Prepare a dilute iron solution (e.g., 1–2% OWF → 1–2 g ferrous sulfate per 100 g wool in a jar of water). After dyeing and rinsing, you can either:

  • Put the dyed wool into a weak iron bath for a few minutes to darken (watch closely — it can go fast), or

  • Add a little iron solution directly into the dye bath at the start for an all-over darker/greyer result.

• Option B — Rusty nails/vinegar (homemade iron): Put rusty nails or iron bits in white vinegar for 24–48 hours to extract iron. Strain the “iron juice” and use small amounts (test first) to darken the dyed wool. Results are less predictable but are very traditional.

CAUTION: Iron will darken quickly. Always test on a small sample.

Aftercare

• Wash dyed wool with a gentle wool wash or mild soap in cool water.

• Avoid hot water and harsh agitation (they cause felting).

• Colours from natural dyes may mellow slightly after the first wash.

Troubleshooting & tips

• Too light: Re-dye in the same bath (the acorn bath can often be reused once or twice). Let the wool cool in the bath longer.

• Felting: Temperature too high or too much agitation, be gentler next time, and never boil wool.

• Colour washes out: Ensure proper mordanting. Use alum mordant and acidify the bath slightly.

• Uneven colour: Make sure wool is wet through and moves freely in the bath. Avoid crowding. Stir very gently when adding to the dye bath to keep the wool submerged and even.

• Variability: Acorn species, ripeness, soil, and water pH all change results — embrace the uniqueness!

What colours to expect

• Without iron: warm tan → golden brown → rich chestnut depending on concentration and steep time.

• With iron modifier: olive → slate grey → charcoal/black (iron darkens and shifts tannin colours toward grey/black).