Two Dyes, One Warm Palette

Brown onion skins and madder root are the pair I recommend to anyone beginning a natural dye journey. They are forgiving, widely available, and they sit beside each other beautifully on the same piece of cloth. Onion skins give you amber, honey, soft gold and a faint bronze, depending on the fibre and the mordant. Madder root, the ground-up root of Rubia tinctorum, gives the true reds that have coloured British wool and linen for centuries — brick, coral, rust and a deep rose.

Both respond well to the same alum mordant, which means you can mordant one batch of yarn or cloth, dye half in skins and half in madder, then overdye the amber skeins in the exhausted red bath to produce terracotta and burnt orange. That economy of process is the real pleasure of working with these two.

Gathering and Preparing Onion Skins

You need a surprising quantity of skins. Keep a paper bag by the kitchen and add to it whenever you cook — red skins shift the colour towards olive and bronze, while brown and yellow skins give the cleanest amber. Dried skins keep for months in a cool, dark cupboard.

For a strong amber on wool, use the skins at roughly 100% of the weight of fibre to be dyed — so 100g of dry skins for 100g of yarn. Halve that for pale gold. Cover the skins with water, bring to a gentle simmer and hold for 45 to 60 minutes. Do not boil hard; a rolling boil clouds the colour and can make it muddy. Strain the liquor through a muslin square, pressing the skins to extract everything, then return the clear liquid to the pot.

• Wet your fibre thoroughly before it enters the bath — dry wool takes up colour unevenly.
• Simmer the fibre in the strained liquor for 45 to 60 minutes, stirring gently and often.
• Leave the fibre in the cooling bath overnight for a deeper, more even tone.

Madder Root: Patience Rewarded

Madder is where beginners come unstuck, and the culprit is always temperature. Above about 70°C the red begins to turn brown, and a hard boil will ruin a batch within minutes. Keep the bath at a steady 60 to 70°C — a gentle steam, never a bubble — and you will be rewarded with a clear, rich red.

Use madder at 50 to 100% of the weight of fibre. Roots give a more orange, rust-toned result; older, finely ground madder tends to be redder. Soak the root in warm water overnight before dyeing, then add the fibre and hold it at temperature for 45 to 60 minutes. Turn off the heat and let everything sit in the bath until completely cold; this slow cooling is where much of the depth develops.

Water matters more with madder than with almost any other dye. Hard water, rich in calcium, pushes the colour towards a true red, so if your supply is soft, add a teaspoon of calcium carbonate or a little chalk to the bath. Soft water alone will leave you with salmon and orange.

Mordanting Safely and Effectively

Mordants are metal salts, and they should be treated with respect. Alum — potassium aluminium sulphate — is the safest and most reliable choice for both dyes. Use it at 10 to 15% of the weight of fibre, with 5 to 8% cream of tartar to brighten the colour and soften the hand of the wool.

Dissolve the alum in hot water, add enough water to cover your fibre freely, then add the fibre once it is wet out. Hold at 60 to 80°C for an hour, then leave it in the cooling bath for at least 24 hours. Rinse lightly before dyeing.

• Keep dedicated stainless steel or enamel pans for dyeing, and never use them for food afterwards.
• Wear gloves, work in a ventilated space, and label every container clearly.
• Avoid chrome, tin and copper mordants — they are toxic, and tin makes wool brittle.
• Cellulose fibres such as cotton and linen need a tannin pre-treatment before alum; wool and silk do not.

Shifting the Colour

Once your fibre is dyed, small adjustments can transform it. A brief dip in a weak iron bath — a teaspoon of ferrous sulphate in a bucket of water, or water left standing with rusty nails — saddens onion-skin amber to olive-brown and deepens madder red to a maroon-plum. Dip for five to fifteen minutes only, rinse at once, and use iron sparingly; in quantity it weakens fibre over time.

Acid shifts madder towards orange, so a splash of vinegar will warm it. Alkali, such as a pinch of washing soda, pushes it towards pink, though wool dislikes strongly alkaline baths. Overdyeing an onion-skin skein in a madder bath gives a lovely terracotta, and an exhausted madder bath will still tint a batch of pale gold.

Rinsing, Drying and Everyday Care

Rinse dyed fibre in cool water until the water runs clear, then wash gently with a pH-neutral soap. Dry in the shade; direct sunlight fades onion-skin yellows noticeably and will dull madder over a season. Wash finished pieces by hand in cool water with a mild, non-enzymatic soap — enzyme detergents digest wool — and store them away from bright light. Treated this way, madder holds its colour remarkably well, and your amber will soften gracefully rather than disappear.