Natural Dyeing with Onion Skins and Madder Root

Two dyes worth knowing

Onion skins and madder root sit at opposite ends of the natural dyeing spectrum, which is exactly why they work so well together. Onion skins are free, endlessly available and forgiving — the papery outer layers of brown onions give warm golds, honey tones and coppery ambers, while red onion skins lean towards soft pinkish-olives. Madder root, the dried root of Rubia tinctorum, is the classic European red: brick, terracotta and, with the right handling, a clear deep rose. Between them they cover most of the earthy palette a UK maker is likely to want for wool, linen or silk.

Both dyes reward the same approach: gentle heat, patience, and a notebook. Neither needs expensive equipment. A dedicated stainless steel or enamel pan, a sieve, a jam thermometer and a bag of alum will get you a long way.

Gathering, scouring and mordanting

Start collecting brown onion skins in a paper bag and keep them dry. A loosely packed carrier bag of skins weighs roughly 30–40g, so it takes a few weeks of cooking to build up a useful quantity. As a rule, use 50–100% of the fibre weight in skins (100g of skins for 100g of wool); the higher figure gives richer, more saturated colour. Red onion skins should be kept in a separate bag, as they behave quite differently.

Before any dyeing, scour protein fibres — wool and silk — in hand-hot water (around 40°C) with a squirt of pH-neutral washing-up liquid or a dedicated wool scour. Leave for 20–30 minutes without agitation, then rinse gently. Never shock wool with temperature changes; it will felt. Linen and cotton need a longer, hotter scour with a little soda ash to remove the natural waxes.

Mordanting is the step that decides whether your colour lasts or washes straight out:

• Alum (potassium aluminium sulphate) at 10–15% of the fibre weight, plus cream of tartar at 5–8%, is the workhorse for wool and silk.
• Dissolve the powders in hot water, top up the pan so the fibre can move freely, then add the damp fibre.
• Raise slowly to 80–85°C and hold for 45–60 minutes. Do not boil wool.
• Let the fibre cool in the bath overnight, then squeeze rather than wring.
• Cellulose fibres need a tannin pre-treatment before the alum, or the colour will be pale and fugitive.

Keep dye pots strictly for dyeing, wear gloves, work in a well-ventilated space and label every jar of powder clearly.

Simmering onion skins

Cover the skins with water — rainwater if you have it, since soft water keeps golds clear — and bring to a gentle simmer for 45–60 minutes. The liquid should end up the colour of strong tea. Strain out the skins, pressing them to release the last of the colour, and compost the solids.

Return the bath to around 80°C, add your wet mordanted fibre and hold for 45–60 minutes, turning it occasionally with a wooden spoon so the colour takes evenly. Then turn off the heat and leave the fibre in the cooling bath. Overnight is not too long; the colour will continue to deepen. Rinse in water of a similar temperature until it runs clear, then dry in the shade.

Madder root: gentle heat, deep reds

Madder is far less forgiving than onion skins. Its reds are easily ruined by high heat, which pushes them towards dull brown. Soak chopped or powdered madder root overnight in soft water, using 50–100% of the fibre weight, then warm the bath slowly and hold it at 55–60°C for 60–90 minutes. Keep a thermometer in the pan and resist the urge to hurry.

A teaspoon of chalk (calcium carbonate) per 10 litres of water helps the reds read cleanly, and hard water generally suits madder better than soft. Alum-mordanted wool gives a warm orange-red; add a tannin-rich pre-mordant if you want the colour to shift towards a deeper brick. Never use an iron pot, and never boil the bath.

Shifting colour with modifiers

Modifiers are where a single dye bath becomes a whole palette. Split your fibre into small skeins before dyeing, then dip each one briefly after the main bath:

• Vinegar (acidic) brightens onion-skin golds and lifts madder towards orange.
• Washing soda (alkaline) deepens onion skins to copper and shifts madder to a rosier, slightly purplish red.
• Iron water, used sparingly at around 2% of the fibre weight, saddens colours to olive, slate and aubergine. A little goes a very long way.

Dip for 5–15 minutes, rinse thoroughly, and keep iron in its own dedicated jar. Remember that modifiers also affect lightfastness, so test before committing a whole project.

Recording results to build a palette

A dye notebook is the difference between a happy accident and a repeatable colour. For every batch, record the date, fibre type and weight, mordant and percentage, dye material and percentage, water source, temperatures, timings and any modifier used. Note the weather if you are drying outside — it genuinely makes a difference.

Then cut a small sample of each result and stitch it to a labelled card, with the recipe written on the back. Within a season you will have a shoebox library of golds, coppers and reds that you can match against a customer's request or a new design. Plant dyes are variable by nature, but good notes let you get close to the same colour every time — and that is what turns a kitchen experiment into a craft you can rely on.