The exothermic perm

An alkaline perm that arrives in two bottles

Strip the name away and an exothermic perm is an alkaline cold wave. The reducing agent is a thioglycolate, the alkali carries it into the cortex, the pH sits inside the same regulated range as any ready-to-use lotion sold here, and the service finishes with a conventional oxidiser. Nothing about the chemistry is exotic.

What differs is the delivery. The product comes as two parts: the waving lotion, and a smaller bottle of activator. The stylist pours the second into the first at the station, shakes it, and the bottle warms perceptibly in their hands within seconds. That warm mixture goes straight onto the wound rods, so the heat arrives with the lotion rather than being blown at it afterwards.

The point is that the heat travels in the bottle. No hood, no cap, no cable, no sitting still under an apparatus for half an hour.

Once mixed, it has to go on at once. The warming reaction is spent in ten or fifteen minutes whether or not it has met your hair, so an exothermic lotion left standing on the trolley is just a cooling alkaline lotion. That is why you see it mixed in front of you and applied at speed, and why it is a professional product rather than a boxed one.

Level of change

The teCsture Scale runs from 1, the tightest pattern, to 10, poker straight — one ladder, ten rungs. What a treatment does is move you a number of rungs. That distance is the job, and it is what the work should be priced on: the level of change, not the bottle.

Broadly an alkaline result, arrived at a little faster and landing a shade softer.

Alkaline chemistry with its own warmth behind it.

What the warmth buys, and what I am not going to tell you

Heat does one thing in a perm and it does it reliably: it makes the reaction go faster. Warmth lifts the cuticle further and drives the reducing agent into the cortex more quickly and more evenly, which matters most on the hair hardest to get into.

The practical results are three. Processing is quicker. Penetration is more even across a head where some sections resist more than others. And the finished curl reads slightly softer than a straight cold wave on the same rods, because a warm reaction reaching a given point needs less contact time to get there. That is the trade the category exists to offer: most of a cold wave’s grip, arrived at faster, with a little less of its hardness.

Exothermic and endothermic

Two words, opposite arrangements of one idea. Exothermic means the reaction gives heat out — this page. Endothermic means it takes heat in, which is the true acid perm: a lotion so mild it cannot get into the hair unaided and needs half an hour under a hood dryer. One brings its own warmth, the other has to be given it, and neither should be run cold.

The activator

I am not going to name what is in it, and I would rather explain why. Formulations differ between houses and are not published in full. The description that circulates most widely has an oxidising agent doing the warming — a strange thing to propose inside a lotion whose whole job is reduction, and not a claim I can stand behind. So: the warming is real, it is deliberate, it comes from mixing two supplied parts, and the route it takes belongs on the manufacturer’s technical sheet rather than on a website. Anything more specific is a guess dressed up.

“Self-timing” was never a mechanism

This is why the page exists. Through the 1980s and 1990s these systems were marketed as self-timing, sometimes as self-neutralising, on a reasoning that sounds plausible for about four seconds: the warmth fades after ten or fifteen minutes, therefore the perm has finished.

It has not. Warmth speeds a reaction up; it does not make it stop. The reducing agent goes on opening disulphide bonds for as long as it sits in the hair, at whatever temperature it happens to be by then. When the bottle cools you have the same lotion working at ordinary room temperature — precisely the condition a cold wave works in all day long. The heat phase ending is not an ending.

A perm stops when it is rinsed out and an oxidiser is applied. Nothing else stops it, and no lotion has ever stopped itself.

“Self-neutralising” is worse, because neutralising is a separate step: an oxidiser rebuilding the bonds in their new positions on the rod. No exothermic system supplies that from inside the mixture, and skipping it leaves the hair chemically unfinished. See neutralising a perm.

What this means in the chair

A self-heating lotion still has to be watched on a test curl, exactly like any other: the stylist unwinds a rod part-way and looks at whether the S has formed to the diameter of the rod, and keeps looking until it has. The words on the box do not change that, and a reaction running faster than a cold wave makes attention more important rather than less.

If you are ever offered a perm on the grounds that it times or neutralises itself, that is the moment to ask a second question. It is not a small exaggeration. It describes something that does not happen.

Resistant hair, a shorter appointment, and where the answer is no

The case for it is narrow and real. If your hair is thick, coarse and stubbornly resistant — the hair that shrugs off a mild lotion and gives you a blow-dry for the price of a perm — the warmth genuinely helps the chemistry reach the cortex, without a hood dryer and without the sit that goes with one. On mixed heads it evens out the gap between a resistant crown and a porous nape, and it is a sensible answer for hair that has under-processed before on a room-temperature lotion.

Where it stops being sensible

On fine hair it is the wrong tool — not because it is uniquely aggressive, but because it is faster, and speed is what fine hair gives you no margin for. Warmth on a fibre with nothing to spare shortens an already short window between a good curl and hair that softens early, will not hold the rod and parts under low load. Work cold and watch it, or work further down the ladder.

Where the answer is no

On bleached hair, usually no — and usually is doing real work in that sentence. Highlights count. Foils count. Grown-out bleach still sitting on the lengths counts. Bleaching oxidises cystine to cysteic acid, and a neutraliser needs two sulphur atoms it can no longer find, so most bleached or highlighted hair takes a curl that drops out within weeks while the hair pays for it. That is the default and the default is no, and adding heat to the service is the opposite of what would soften it. But it is a judgement made on the hair in front of me — how much lightener, how long ago, how much has grown out, what condition the rest is in — and occasionally, in the right hands and at the right strength, it is possible. Assume no, and come and let me look rather than deciding from a page. See bleach damage.

Also no over a hydroxide relaxer, in either direction and at any interval, because hydroxide removes one sulphur permanently and there is no route back from that. Whether your own hair is a candidate for any of this is the subject of can your hair take a perm.

What the service involves, and how warm it actually feels

Elasticity test, then a gentle clarifying wash. A wet strand stretched and released; if it draws out and does not come back, the appointment should end here. The scalp is not scrubbed — and do not scrub it yourself in the two days before either, because an alkaline lotion on abraded skin stings.
The wind, thirty to forty-five minutes. The rods author the shape, so this is where the result is decided.
Mixing, at the station, in front of you. Activator into lotion, shaken, and the bottle changes temperature in the stylist’s hands. This is the step that identifies the system.
Application, quickly. Every rod, without delay, because the warming reaction has already started.
Processing, watched. Shorter than the cold equivalent, and judged on test curls rather than the clock.
Rinse, blot, neutralise. Warm water for five to ten minutes to flush the alkalinity, every rod blotted so water does not dilute the oxidiser, then the bonds close in their new positions.

How warm does it feel on my head

Warm, not hot. A spreading warmth through the wrap, closest to a towel out of the airing cupboard, strongest in the first few minutes and fading as the reaction spends itself. You should be aware of it and comfortable with it throughout.

I am deliberately not printing a temperature figure next to that question, and the reason is practical rather than coy: a number on a website gets reproduced at home with an appliance, and warmth made inside a formulated mixture is not the same thing as heat applied from outside. It should never sting, burn, or feel like a hot point on the skin. That is not the thermal reaction working — it is lotion meeting broken skin, and the right response is to say so at once rather than sit politely through it.

How long it lasts, and the first three days

Four to six months on the treated lengths, sometimes longer, and like any thioglycolate wave it grows out rather than disappearing. Expect a visible line where new straight hair meets the curl; hair grows about half an inch, a little over a centimetre, a month, so that line is a planning question.

It sits a shade below a straight cold wave for durability, which is the other half of the trade for a softer result. If longevity is the whole point, the answer is the cold version and a longer sit.

The first seventy-two hours

Seventy-two hours. Neutralising reforms the bonds but it does not finish the job on the spot — oxidation carries on in air and the fibre keeps hardening for about three days. In that window what you press into the hair tends to stay: no tight ties, no clips, no hard brushing, and go gently with heat. Beyond that, follow the washing instruction for the product actually used on you rather than a rule someone learned thirty years ago.

Afterwards the cuticle does not lie quite as flat as it did, so the hair reads drier than it used to. Sulphate-free washing, weight in the conditioner, no brushing when dry. London water is hard and permed hair is porous, so a chelating shampoo every three or four weeks keeps calcium from stiffening the curl.

An old idea, and where it sits now

Chemically generated heat at the rod is not a 1980s invention. It is how the trade escaped the electrical waving machine: from 1933 a wound curl could be covered with a small sealed pad of quicklime that hydrated and gave out heat where it sat, and within five years the self-heating envelope was the ordinary thing. The principle carried over, the formula did not — that pad never touched the hair, supplying temperature while a separate lotion did the softening. A modern system makes its warmth inside the lotion itself.

It is a smaller category now, and worth knowing that at least one major house still treats it as a class of its own rather than a variant. Zotos Professional’s current perm reference chart sorts the whole range into four classes — acid, alkaline, exothermic and thio-free cysteamine — and its Quantum range spans three of them under one name. Hence the rule that runs through this library: read the active ingredient and the class, never the range name.

Against a straight cold wave it is faster, slightly softer and slightly less durable. Against a true acid perm it reaches the same warm processing from the opposite direction, without the dryer and without the sit.

Questions

What actually makes an exothermic perm heat up?

Mixing the two supplied parts. The activator poured into the waving lotion sets off a reaction that releases energy as heat, so the mixture warms in the bottle and goes onto the rods already warm. I will not print a formula: the descriptions in general circulation do not survive checking, and the one repeated most often has an oxidiser doing the warming inside a reducing lotion, which makes no chemical sense.

Are exothermic perms self-timing?

No, and there is no mechanism behind the word. Warmth speeds a reaction up; it does not make it stop. When the heat phase ends you are left with an ordinary alkaline lotion still opening bonds at room temperature. It has to be watched on a test curl, rinsed and neutralised, exactly like every other perm.

Do I have to sit under a hood dryer?

No — that is the functional point of the category. The heat is made in the mixture and arrives with the lotion, so nothing has to be blown at your head. A true acid perm is the one that needs the dryer, for twenty to thirty minutes.

Is it gentler than a normal alkaline perm because the curl is softer?

Not gentler, quicker. The reducing agent and the pH are much the same; what changes is how fast it reaches the cortex and therefore how long it sits there. On resistant hair that is an advantage. On fine hair it is the opposite, because speed removes the margin a stylist relies on.

How hot does it get on my head?

Warm rather than hot — a spreading warmth through the wrap that fades as the reaction spends itself, and you should be comfortable throughout. I do not publish a figure for it, because a number on a page gets copied at home with an appliance that behaves nothing like a formulated mixture. If it stings or feels like a hot point on the skin, say so and have it rinsed. That is not the reaction working.

How long does it last?

Four to six months on the treated lengths, and often longer. It grows out rather than dropping out, so plan for the line at the roots. A cold alkaline wave holds a little longer, which is the price of the softer, faster result here.