Plenty of colour hiding in plain sight

You do not need a dedicated dye plot or a shelf of imported powders to colour wool and cotton. An ordinary British garden, allotment or hedgerow supplies more than you would think: dry brown onion skins from the kitchen, the first nettles of spring, and madder root if you are willing to give it a corner of the border and a few years of patience. The colours are soft and earthy rather than vivid, which is exactly what makes them wearable, and each dyebath is a small experiment you can repeat, adjust and improve next season.

Before you begin, put aside one large stainless steel or enamelled pan that will never again be used for food. Dyeing is safe in itself, but mordants leave residues you would rather not find in your soup. A pair of tongs, a sieve, some old scales accurate to a gram, and a notebook complete the kit.

Preparing fibre: scouring and mordanting

Dye clings poorly to greasy or unwashed fibre, so start with a scour. For wool, steep in hot water with a little pH-neutral soap or washing-up liquid at around 50°C, agitate gently and rinse until the water runs clear. Cotton is tougher and needs more persuasion: simmer it for an hour with a teaspoon of soda ash per litre, then rinse thoroughly.

Next comes the mordant, the metal salt that fixes colour to fibre. Alum — potassium aluminium sulphate — is the safest and most forgiving choice. Use it at 10–15% of the dry weight of the fibre, known as weight of fibre or WOF, with 6–8% cream of tartar. Dissolve both in hot water, add the wetted fibre, hold at about 80°C for an hour without boiling, then let it cool in the pan overnight. This single step is the difference between a pale wash that fades in a fortnight and a colour that survives years of washing. Cotton benefits from a tannin pre-treatment first: simmer it in strong tea or oak galls, rinse, then mordant with alum as above.

Onion skins: the reliable first dyebath

Brown onion skins are the ideal introduction because they are free, endlessly available and almost impossible to get wrong. Save them in a paper bag through the winter; you want roughly the same weight of skins as of dry fibre, though twice as many gives a deeper result. Simmer the skins in water for 40 minutes, strain them out, then add your mordanted fibre and hold it at 60–80°C for an hour.

• On alum-mordanted wool, brown skins give a warm copper-orange that softens to apricot as it dries.
• The same bath on cotton is paler and more muted, closer to a dusty peach.
• Red onion skins push towards olive and bronze rather than pink, so do not expect raspberry.
• Save the exhausted bath — a second and third dip will still colour fibre, just more faintly.

Nettles: fresh green from the verge

Nettles are at their best for dyeing in April and May, before they flower. Wear gloves, cut only the top few inches, and take them from hedgerows away from busy roads, sprayed verges and popular dog-walking routes. You need roughly equal weights of fresh nettle and dry fibre. Simmer the chopped plants for an hour, strain, then dye mordanted fibre for an hour at 60–80°C.

Straight from the pot the result is a soft yellow-green, brighter on wool than on cotton. Nettle dye responds beautifully to an iron afterbath, which saddens it towards sage, olive and deep khaki — the colours of a February hedge. If you want a stronger green, add a handful of yarrow or tansy to the pot alongside the nettles.

Madder root: the true red, if you are patient

Madder is the classic British red, a root harvested from plants at least three years old. Lift roots in autumn, wash them, and dry them somewhere airy; they will keep for years and can be chopped or ground as needed. Use 1:1 to 2:1 root to fibre, soak overnight, then simmer gently for an hour and strain.

Here is the important part: keep the dyebath below 70°C. Boil madder and the lovely red turns to dull brown, because the heat releases unwanted brown pigments along with the alizarin. Dye for one to two hours, then leave the fibre in the cooling bath overnight for the fullest colour. Madder likes hard water, so if yours is soft, add a teaspoon of calcium carbonate to the pot. On alum-mordanted wool you will get brick red and terracotta; on cotton, expect a softer coral pink.

Modifiers, notes and aftercare

Modifiers are how you stretch a single dyebath into a whole palette. Make iron water by soaking rusty nails in a mix of vinegar and water for a week, then use it at 1–2% WOF as a brief dip after dyeing. It deepens and dulls almost everything, turning yellows to olive and reds to plum. Use it sparingly on wool, as too much iron makes fibre brittle. An alkaline dip — a pinch of soda ash in water — pushes madder redder and brighter, while a splash of vinegar warms and lifts yellows.

Always test modifiers on a small sample skein before committing a whole batch. Keep a notebook recording the date, plant and quantity, fibre weight, mordant, temperatures, timings, modifier and the final result, and tie a labelled sample of each dyed skein alongside it. Your records are what turn happy accidents into repeatable recipes.

Finally, treat naturally dyed cloth kindly. Rinse in water of a similar temperature to avoid shocking the fibre, dry in the shade rather than full sun, and wash with a pH-neutral soap. Colours will mellow over the years, but a well-mordanted madder red or onion-skin copper will still be recognisably itself long after a shortcut dye has washed away.