Why Linen Takes Kindly to Plant Dyes

Linen has a natural affinity with the muted, shifting colours of the hedgerow. Spun from flax, it is a cellulose fibre, which means it does not absorb dye in the greedy way wool does — but what it lacks in intensity it more than makes up for in subtlety. The results are soft, chalky and faintly irregular, exactly the sort of colour that sits comfortably in a natural interior alongside bare floorboards, lime plaster and undyed wool.

Two of the easiest and most rewarding dyestuffs to begin with are also two of the most abundant: the papery skins of brown onions, saved through the winter, and heather gathered from the moor in late summer. Between them they cover a range from warm honey gold to quiet sage and olive.

What You Will Need

• A stainless steel or enamel pan, large enough that the fabric can move freely. Avoid aluminium, which dulls colours, and keep any iron pans for modifying rather than dyeing.
• A wooden spoon or long-handled tongs, kept for dyeing only.
• A fine sieve or a square of muslin for straining the dye bath.
• Rubber gloves and an apron — plant dyes stain skin and worktops cheerfully.
• Alum (potassium aluminium sulphate), the mordant that fixes colour to cellulose.
• A little cream of tartar, to soften the mordant's action.
• Washing soda for scouring the linen before dyeing.

Weigh your dry linen first. All quantities are calculated on the weight of fibre, usually shortened to WOF. A metre of medium-weight linen weighs roughly 250g, which makes the sums pleasingly straightforward.

Preparing the Linen

Linen straight from the roll carries sizing, waxes and pectins that will block dye. Scour it first. Dissolve 5g of washing soda per litre of water in your pan, add a drop of gentle washing-up liquid, and bring to around 60°C — hot but not simmering. Add the linen, hold it there for 45 to 60 minutes, stirring occasionally, then rinse until the water runs clear.

Next, a tannin bath. This is optional but transformative on linen, giving both a warmer base tone and a better grip for the dye. Steep the damp fabric in strong black tea — six or seven teabags per 4 litres, brewed and cooled — for an hour, then squeeze out and move straight to mordanting.

For the mordant, use 10% alum and 5% cream of tartar on the weight of fibre. For 250g of linen, that is 25g of alum and 12g of cream of tartar. Dissolve both in a little hot water, top up the pan, add the damp linen, and raise the temperature slowly to 80°C. Hold for 45 to 60 minutes, then leave the fabric to cool overnight in the bath. Rinse before dyeing.

Onion Skins: Gold, Amber and Olive

Save the dry outer skins of brown onions in a paper bag as you cook. You want roughly the same weight of skins as fabric — a generous bagful for a single metre. Simmer them in water for 30 minutes, until the liquid is a deep amber, then strain the skins out. They have given all they have.

Return the liquor to the pan, add your damp, mordanted linen, and heat gently to 80°C. Hold for 45 to 60 minutes, stirring now and then so the colour takes evenly. Turn off the heat and let everything cool in the bath overnight; this slow cooling is where the depth develops.

Brown onion skins give a glowing honey gold. Red onion skins, used the same way, lean distinctly towards olive and tan — a good deal more sophisticated than you might expect from the kitchen bin.

Heather: Soft Sage and Quiet Khaki

Gather heather in late August or September, when the moor is in full flower. Calluna vulgaris is the species you want: snip the flowering tops and a little of the green stem, and use them fresh or dried in a warm airy place. Be generous — heather is a gentle dye and rewards a heavy hand. Aim for at least the weight of your fabric in plant material, and more if you can spare it.

Simmer the heather in water for 45 to 60 minutes, then strain. The liquor will look a promising brownish-green; do not be disheartened, as this is where the magic happens. Add alum-mordanted linen and hold at 80°C for an hour. On linen, heather gives a soft sage-green shading into pale khaki — an excellent colour for cushion covers, table runners and curtain headings. Cool overnight, then rinse in cool water until it runs clear and dry in the shade.

Shifting and Setting the Colour

Half the pleasure of plant dyeing is the way colours can be nudged. A splash of white vinegar, which is acidic, brightens yellows and keeps greens fresh. A pinch of bicarbonate of soda, which is alkaline, warms golds towards brass and rust. Add either to a separate bath and dip a sample first, as a little goes a long way.

For deeper, sadder tones, make a simple iron water by leaving a handful of rusty nails in a jar of water and vinegar for a fortnight. Add it a teaspoon at a time to a fresh bath and watch olive and khaki emerge within minutes. Treat iron with respect — too much makes linen brittle over time, so keep the dose light.

Wash finished pieces cool and gently, with a mild detergent, and dry them in the shade rather than full sun. Expect a slow, graceful fading over the years. In a natural interior, that softening is not a flaw; it is the whole point.