The Science
How Organic Hair Dye Works
Chemical dye forces colour in. Plant pigment is carried in by water and stays there by two entirely different routes. Once you understand which pigment does what, every rule about organic colour starts to make sense.
Almost every disappointing result has a physical cause, and it is usually one of two kinds. Either the pigment never reached your hair, or it reached it and the reaction that develops it was cut short. The symptoms look different, and so do the fixes.
Start With the Strand
Three Layers, Three Roles
Every hair shaft is built from three layers. What a dye has to break in order to work is the entire difference between chemical and organic colour.
Outermost
Cuticle
Overlapping scale-like cells that protect everything inside. Chemical dye must pry these open with an alkaline agent. Organic colour has nothing in it that can.
Middle
Cortex
Holds keratin — the protein your hair is made of — and melanin, which gives your natural colour.
Innermost
Medulla
The soft central core, present mainly in thicker hair types.
Two Different Mechanisms
Bind vs. Break
Water carries the pigment to the protein
Plant pigment dissolved in water reaches the fibre and attaches to the keratin already there. Nothing forces the cuticle open, nothing is stripped away, and no new pigment molecule is assembled inside the strand.
Because there is no bleaching agent, organic colour cannot lighten hair. It only adds. Pick a shade lighter than your own and you get tone and shine — not lightness.
Chemicals open, strip, and build
Ammonia pries the cuticle open and peroxide breaks down the melanin already inside. Small colourless precursors then diffuse in and react into larger coloured molecules in place — now too big to wash back out.
Colour retention is strong — but the cuticle is damaged to achieve it. Hair is dead tissue: it cannot rebuild what the reaction took.
This is also why "chemical-free" is not a phrase we use. Plants are made of chemicals; lawsone is a chemical. What is absent from this pouch is a specific set of them — the ones that open the cuticle, bleach melanin, and assemble dye inside the fibre.
The Part Most People Miss
Two Pigments, Two Ways of Staying
Henna and indigo are both plant pigments, but they do not behave alike at all. One bonds chemically. The other is built in place and physically trapped. Nearly every rule on this page follows from that difference.
Bonds
Henna
Lawsonia inermis
Very little free pigment sits in a henna leaf. It is stored as glycosylated precursors — hennosides — and released as lawsone when water and the leaf's own enzyme get to work on the powder.
Lawsone then forms a covalent bond with keratin, attaching to the fibre rather than resting on it. That is a chemical bond, not a coating.
What follows from this: henna shades are the most wash-fast. They don't rinse off — they wear off as the hair itself wears.
Forms in place
Indigo
Indigofera tinctoria
Indigo leaves hold no blue at all. They hold indican, a colourless, water-soluble precursor. Water releases it as indoxyl, which reaches the outer layers of the fibre while it is still soluble.
Then it oxidises in place into indigo — which is insoluble. The pigment is formed on your hair and physically held there. It never bonds to anything.
What follows from this: indigo can only keep forming while the hair stays damp — and because it sits more superficially, it fades sooner than henna does.
This is why a herbal colour is not finished when you rinse it, why we ask for 72 hours with no shampoo, and why letting hair dry out too fast stops the colour dead. All three are the same fact seen from different angles.
The Question We're Asked Most
Does Any of It Reach Your Scalp?
Probably yes — and "it's natural" is not a reason to think otherwise
This question usually arrives with an assumption attached: that because these are plants, nothing crosses the skin. We would rather correct that than trade on it.
Skin absorption depends heavily on how small a molecule is. The most widely cited threshold in dermatology holds that a compound must be under about 500 daltons to cross the outer layer of skin at all. Henna's pigment is 174. Being a plant molecule does not make it large — if anything, plant pigments are smaller than the synthetic dye precursors people are trying to avoid.
| Compound | Molecular weight | Under 500 Da? | In this pouch? |
|---|---|---|---|
| Lawsone (henna) | 174.15 g/mol | Yes | Yes |
| p-Phenylenediamine (PPD) | 108.14 g/mol | Yes — and smaller | No |
Lawsone: PubChem CID 6755. p-Phenylenediamine: PubChem CID 7814. Threshold: Bos JD, Meinardi MMHM. "The 500 Dalton rule for the skin penetration of chemical compounds and drugs." Exp Dermatol. 2000;9(3):165–169. doi:10.1034/j.1600-0625.2000.009003165.x · PMID 10839713. Note that the rule describes a ceiling, not a guarantee — being under 500 daltons means a molecule can cross, not that it does, or in what quantity.
So the useful question is not whether something crosses. It is what crosses. And that is a question you can answer from an ingredient list rather than from a promise.
What we can tell you
- Twelve herbs, and nothing else. You add water. Every shade's full ingredient order is published.
- No PPD or related dye precursors. These are the compounds behind most hair dye allergy, and the reason patch tests exist.
- No ammonia, no hydrogen peroxide, no resorcinol. Nothing that opens the cuticle or bleaches melanin.
- Certified organic. COSMOS ORGANIC, held since 2012 — which covers how the plants were grown, and that nothing was added afterwards.
What we can't
- How much is absorbed. We have not measured it, and we have not found a study that measures it at cosmetic use levels.
- Whether it is right for your situation. Pregnancy, a medical condition, a treatment you're on — those are conversations with your doctor.
- That "natural" means safe. It doesn't, and anyone telling you otherwise is selling something.
Two things about henna worth knowing before you buy
1 · "Black henna" is not henna. Products sold under that name — usually for temporary tattoos — have PPD added to them to make the stain black and fast. PPD on bare skin at those concentrations has caused severe allergic reactions, and much of henna's poor reputation comes from exactly this. The problem is the additive, not the plant. Pure henna stains orange-red and takes hours.
2 · G6PD deficiency. Lawsone has been linked to haemolysis in infants with G6PD deficiency, an inherited enzyme condition that is more common in people of Mediterranean, African, Middle Eastern and South Asian descent. We are not aware of reports of this at normal adult hair-colouring use — but if this applies to you or your family, it is worth raising with a doctor rather than taking a website's word for it.
If you're asking because of medical treatment
A number of our customers come to us during or after cancer treatment, having already asked their doctors and read a great deal. We can tell you what is and isn't in the pouch, and how it works. We cannot tell you whether it is appropriate for you — that is a conversation with the people treating you, and we would rather you had it.
What we can do is make that conversation easier. Every shade's complete ingredient list, in order of quantity, is on one page — print it, or take it in on your phone. All 24 shades, herb by herb →
On Gray Hair
Two Different Kinds of Beautiful
A gray strand has no melanin left in it. A pigmented strand still has all of its own. Put the same plant pigment on both and you get two different results from one application — the gray shows the pigment's own colour, the pigmented hair shows the pigment over what was already there. That is where the dimension comes from.
20% Gray Hair
Organic colour blends the grays into the surrounding tone. Chemical colour lifts everything to a single flat shade.
30% Gray Hair
With more gray present, the dimensional effect becomes more visible — reading as soft, natural highlights.
Organic Hair Colour
Blends gray rather than blocking it out
Chemical Hair Colour
One uniform shade, edge to edge
Two things to expect. Gray strands take the pigment at full strength, so they read lighter and warmer than the rest — that is the highlighting effect, not a failure. And gray is often the slowest part of the head to take, so give it a heavier layer and more time. The hairline and temples are the hardest place of all, because a cap seals least well there and the paste dries out first. How to keep it damp →
Before You Judge the Result
What It Can and Can't Do
It softens rather than growing out
How long a shade holds depends on which pigments are in it. Henna-based shades last longest, because lawsone is bonded to the keratin and wears down as the hair wears. Shades built mostly on indigo soften sooner, since indigo is held in the outer layers rather than bonded.
Neither grows out in a line. As colour softens, regrowth blends into it rather than drawing a border — which is why touch-ups are more forgiving than with chemical colour.
It cannot lighten hair
There is no bleaching agent in the pouch, so nothing removes the melanin you already have. Plant pigment only adds. Whatever shade you choose, the result can only be darker or warmer than where you started — never lighter.
A swatch shows what the pigment looks like on its own. What you get is that pigment over your hair — so the darker your starting colour, the less of the shade you will see.
Part One — Why Colour Doesn't Take
Five Physical Barriers
Water is the carrier. Anything that blocks water, dilutes it, or lifts pigment back out will weaken your result — and none of it has to do with the product itself. Here is exactly what to avoid.
Conditioner or product residue on the hair
Oils left behind by conditioners and treatments repel the water-based plant pigment solution. The paste cannot make contact with the hair at all, and the colour comes out weak.
What to do: wash with a clarifying, residue-free cleanser before colouring. Skip conditioner, oils, and leave-in treatments on colouring day.
The paste wasn't mixed thoroughly
If the powder is not fully dissolved, the plant pigments clump together. Clumps are too large to reach the fibre — so the pigment sits on the surface and rinses away.
What to do: stir until completely smooth, with no dry pockets or lumps. A yogurt-thick, uniform paste is the goal.
Your hair was too wet
Water already in the hair dilutes the paste on contact. The pigment solution becomes too weak, and the colour that reaches the strand is faint.
What to do: towel-blot until hair is merely damp — never dripping. Damp helps; wet works against you.
Alkaline water washed the pigment out
Lawsone holds best in mildly acidic conditions. In alkaline water it holds less well, and colour can lift back out during rinsing.
Most relevant for the shades where henna leads the list — Auburn Red, Mahogany and Burgundy. Rinse with cooler water and avoid extended washing. Hard water →
Alkaline shampoo stripped the colour
Soap sits high on the pH scale, around 9–10 — well above the natural range of hair. That alkalinity lifts lawsone back out, and combined with alkaline water it can leave hair both tangled and faded.
What to do: no shampoo of any kind for 72 hours after colouring. Water only. An acidic rinse is not a substitute either — acid works against indigo, which is still developing.
Three More Things That Change It
Not Mistakes — Just Variables
These aren't things you did wrong. They are properties of your hair, your water and your method that shift the result — and knowing about them ahead of time is the difference between an unwelcome surprise and an expected one.
How readily your hair takes water
If water beads before soaking in, or your hair takes a while to get properly wet, plant colour will be slower to take. Add 30 to 60 minutes.
If it soaks up water instantly — often previously bleached or heat-damaged hair — pigment goes in fast and can land darker or cooler than the swatch. This is a rough guide rather than a measurement; we are not aware of a reliable home test for it.
Processing time
Under-development is one of the most common causes of a weak result, and the easiest to fix. Different shades need different times — a henna-forward red does not want the same hour as an ash tone built on indigo alone.
Warmth helps, but only if the paste stays damp: a cap keeps both. Times by shade →
Minerals in your water
Dissolved iron reacts with plant polyphenols to form dark complexes — the same chemistry behind iron gall ink. Where iron is present, a result can come out duller, greyer or darker than expected.
Calcium behaves more like residue, coating the fibre and blocking contact. Hard water →
Part Two — When It Went In But Never Finished
The Reaction Needs Water
Everything above is about pigment failing to reach your hair. This is the opposite problem: the pigment got there, and then the reaction that develops it was cut short. The result looks completely different, and so does the fix.
Drying your hair after you rinse.
Remember that indigo isn't bonded — it is formed on your hair, and it can only keep forming while the hair stays damp. Dry it fast and you take the water away before the reaction has finished.
The problem is the drying, not the heat — a cool setting is no safer than a hot one. And the reaction does not resume later. We tested this on grey swatches: the blow-dried sample stopped developing, shifted further towards warmth by 72 hours, and re-wetting it afterwards did not bring the colour back. See the test →
Right after rinsing
Green, and that's normal
Barely any indigo has oxidised. Green is the stage it passes through — not a failed result. You see it most on grey or light hair, where nothing hides it.
Day one to two
The green clears
The tone keeps deepening for as long as the hair holds any moisture.
Day three
The tone lands
This is the colour you'll be wearing. Shades with no indigo settle faster — those you can judge after a day.
This is also why we ask for 72 hours with no shampoo
It isn't only that alkaline shampoo lifts lawsone back out, though it does. It's that the reaction is still running for those three days. Washing interrupts a process that hasn't finished.
And if it has already stalled, we have to be straight with you: it does not reverse. We used to suggest that dampening the hair could restart it. We tested that, and it doesn't. What does work is colouring again — the same shade, or indigo on its own — and air-drying that second application. A purple result → · Red or copper → · Green — usually normal →
An Important Distinction
Clarify Before, Never After
A strong cleanser is useful on the day — and only on the day
This confuses people, so it is worth stating plainly. Timing is everything. A strong or alkaline cleanser strips oils, silicones and styling residue — exactly what you want gone before the paste goes on, and exactly what you must avoid afterwards, when the same property lifts pigment back out.
Before colouring — clarify
Wash thoroughly, skip conditioner. Our soap-based Organic Shampoo Bar is alkaline, which makes it genuinely useful here: it clears the residue that would otherwise block a water-based paste.
After colouring — water only
For 72 hours, the same alkalinity works against you. No shampoo of any kind, and no acidic rinse either — acid holds indigo back while it is still developing.
Now You Know Why
Plant colour is predictable once you know what carries it, what blocks it, and what it needs in order to finish. If your first result wasn't what you expected, we'll send a free alternate shade or refund the colour — we'd rather hear about it than have you write it off.
For first-time customers. No argument required.