Colouring coily hair: plant-based or chemical, what your hair can take

You've got a photo saved on your phone, a deep auburn or a warm brown, and one question: can my hair take it? The answer depends less on the colour than on the process used to get there.

The two families don't act on the same part of the fibre, don't need the same precautions, and aren't cared for in the same way. Here's what sets them apart, what to check before you start, and what happens to a colour over the weeks that follow. One point applies to both: you don't colour a fibre you haven't first brought back into good condition. Our step-by-step tutorial walks through the six steps of the Rituel Texture®.

What each type of colour does to the fibre

An oxidation colour, the kind usually called chemical, works inside the hair. An alkaline agent swells the fibre and lifts the scales of the cuticle, an oxidant removes some of the natural pigment, and the colour develops in the cortex. That's the mechanism that makes lightening possible, and it's exactly the same one that leaves the fibre more porous than before.

Plant-based colour works differently. Plant powders deposit their pigment on the surface, on the cuticle, without opening it and without removing anything. So it can't lighten: it darkens, it tints, it adds tones. In return it coats the hair, and many women find their lengths feel thicker after an application.

On coily hair, this difference matters more than elsewhere. The fibre grows in a helix, every bend is a weak point, and anything that makes it more porous comes back to haunt you at detangling time weeks later. That's not an argument against oxidation colour, but an argument for trusting it to someone who knows this texture, and for not following it with another chemical process.

What plant-based colour can do, and what it can't

Behind the word "plant-based" there are only a handful of plants. Henna, Lawsonia inermis, gives coppers and reds. Indigo, Indigofera tinctoria, is used to darken, almost always as a second application or in a blend. So-called neutral henna, which is actually cassia, adds very little colour: it's used to coat without changing the shade, or to soften a blend that's too coppery.

You can't pick the result from a colour chart: it depends on the colour you already have, and two heads of hair won't give the same result with the same paste. The strand test isn't a nice-to-have, then. It's the only way to know.

Three limits are worth knowing before, not after. Plant-based colour can't be removed: it doesn't strip out, it fades with growth and trims, and it complicates any oxidation colour for months. Despite its reputation as a treatment, it often leaves the fibre drier for the first few days, and a round of Le Masque Réparateur during the week sets things right. Finally, it lasts for weeks rather than months. On the other hand, regrowth doesn't leave a sharp line, and that's its most comfortable advantage day to day.

The part that gets skipped: allergy

This is the part articles on hair colour rush through the most, and it's the only one that can send someone to A&E.

Oxidation colours contain dyes from the phenylenediamine family, including p-phenylenediamine, often referred to as PPD. These are regulated substances: the European regulation on cosmetic products lists them among restricted substances, with conditions of use and mandatory warnings on the packaging. That's why the instructions call for a sensitivity test forty-eight hours before application, even for someone who has been colouring their hair for years: an allergy can appear at any time.

One particular case concerns us closely. Back in 2013, the French medicines safety agency (ANSM) warned against black temporary tattoos sold as "henna" tattoos, to which para-phenylenediamine is illegally added to get a fast, long-lasting black. The reactions they cause can lead to a sensitisation that never goes away, particularly to permanent hair dyes. Many of these tattoos were done on holiday, as a teenager, and long forgotten. If you've ever had one, tell your hairdresser before they open the tube.

The question of henna purity

Pure henna contains just one thing: the ground plant. The word matters, because the shelves are full of blends that carry the same name without having the same composition.

Some products sold as henna are so-called compound hennas: they contain metallic salts, added to fix or alter the shade, which can react when they come into contact with an oxidation colour. That's why many hairdressers refuse to colour over a henna whose composition they don't know. It isn't unwillingness, it's caution. Other products are sold as "black henna": but henna doesn't give black, it gives copper. A blend that promises a true black in an hour isn't a plant product, and it's the same misuse as in temporary tattoos.

The check takes one line: the ingredient list should name the plant or plants, and nothing else. And however much you trust the product, test it on a strand taken from the nape before treating your whole head.

Plant-based colour, step by step

The order matters more than dexterity.

1. 01
   Prepare the pasteMix the powders with hot water until smooth and as thick as yoghurt, then leave to rest for the time given by the manufacturer.
2. 02
   Test on a strandAlways, on a strand taken from the nape. You can't predict the result from a photo or a colour chart.
3. 03
   Apply section by sectionOn clean, dry, detangled hair, generously, from roots to ends. Gloves, an old towel, and a little rich cream around the hairline and ears.
4. 04
   Leave on under cling filmFor the time given by the manufacturer, often several hours depending on the shade. It's long, and that's the price of a process that doesn't open the fibre.
5. 05
   Rinse with clear waterNo shampoo, until the water runs clear. Wait forty-eight hours before the first wash, to give the colour time to settle.

None of this is difficult; what is difficult is the time. A plant-based colour takes half a day, from mixing to rinsing, and that's often why people prefer to have it done. Our directory of partner salons lists hairdressers trained in coily textures, several of whom work with plant-based colour.

Caring for a colour

Coloured hair loses water faster, whatever the process. So the answer isn't more products, but keeping up the rhythm of the full Rituel Texture®, every seven to ten days. It starts with a gentle clarifying cleanse, followed by the sulfate-free Le Shampoing Réparateur, which cleans without stripping the pigment. Next comes Le Masque Réparateur, left on for ten minutes on towel-dried hair, under a cap if you have one. It's through this mask-coated fibre that the Peigne de Man Dol' passes, at step 04, from ends to roots.

La Crème Coiffante then goes on damp hair: it helps hold on to the moisture brought by the wash and prepares for drying. Between two routines, a drop of light oil on the ends can top things up, no more. A colour isn't preserved under a layer of butter, and coloured lengths don't cope well with build-up. Our method to moisturise coily hair applies as is.

That leaves the sun, a colour's number one enemy and the most underestimated. Sunlight alters the colour of hair, its protein content and its strength, and coloured hair is more exposed, lacking intact melanin to absorb some of it (Dario, Baby and Velasco, Journal of Photochemistry and Photobiology B: Biology, 2015). A scarf or a hat during the strongest hours does more for a colour than any treatment applied afterwards. Our tips for summer and the beach apply doubly here.

Where we stand on relaxers

It comes up often enough in your questions to be set down in black and white: we don't do relaxers and we don't offer them. That's not a judgement on those who wear them, it's a decision of method; when a client is set on one, we explain and refer her to a professional who does them.

What concerns us here is narrower: a relaxer and an oxidation colour are two chemical transformations, and combining them calls, at the very least, for the opinion of a hairdresser who knows this texture, in the salon and with the hair in front of them. For a smooth result without chemicals, see our article on straightening without chemicals.

Frequently asked questions

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Sources

• Regulation (EC) No 1223/2009 of the European Parliament and of the Council on cosmetic products, Annex III, restricted substances, including p-phenylenediamine.
• Agence nationale de sécurité du médicament et des produits de santé (ANSM), "Tatouages éphémères noirs à base de henné", warning of 30 July 2013.
• Dario M. F., Baby A. R., Velasco M. V. R., "Effects of solar radiation on hair and photoprotection", Journal of Photochemistry and Photobiology B: Biology, vol. 153, 2015, pp. 240-246.