The Alkaline Perm

Ammonium thioglycolate, and the alkali that carries it in

Two things matter on the label of an alkaline perm and they do different jobs. Ammonium thioglycolate is the reducing agent — the molecule that opens the disulphide bonds holding your hair in its present shape. Ammonium hydroxide is the alkali, and it is there to raise the pH so the thioglycolate can get in at all. The smell everybody remembers is the second ingredient, not the first.

Your hair and scalp sit at about pH 4.5 to 5.5. An alkaline lotion sits at about 9 to 9.5, and because pH is a logarithmic scale that is a very long way from where the hair lives. At that pH the cuticle swells and lifts, the fibre softens, and the thioglycolate reaches the cortex quickly enough to work at room temperature. No dryer, no cap, no machine — which is the whole trick of the cold wave, and why it displaced the heated machine perm inside a decade. See pH and perms.

Nine and a half is not a house preference. It is the ceiling: a ready-for-use perm lotion sold in Britain or the EU may not exceed pH 9.5, with thioglycolic acid capped at 8 per cent for general sale and 11 per cent for professional use.

So when a page or a rep quotes a figure above that, they are describing something that cannot legally be sold to you here. The strongest lotion on the trolley sits at the top of a regulated range, not beyond it.

One variant of this chemistry does not arrive in a single bottle. An exothermic perm is an alkaline perm with an activator mixed into the lotion at the chair, which warms it and speeds the reaction up. It has its own page. Everything else here applies to it.

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.

An alkaline wave is the biggest single move available on the Up side. On straight hair in good condition it will take you four to seven rungs down the ladder, and it will hold there.

Where the reaction stops, and what stops it

Reduction is only half a perm. The lotion opens bonds; the rod decides which sulphur atom ends up next to which; an oxidiser then closes them in their new positions. Miss the second half and you have softened hair and nothing else — see neutralising a perm.

The interesting question is what stops the opening phase before it goes too far. In a modern lotion it is not only the clock. Read the ingredient declaration of a current professional alkaline perm and you will typically find four things: ammonium hydroxide, ammonium thioglycolate, water — and diammonium dithiodiglycolate, which is thioglycolate in its oxidised form. It is a buffer. As the proportion of broken bonds rises, the dithiodiglycolate pushes the reaction back the other way, so the lotion slows itself as it approaches roughly 20 to 30 per cent bond cleavage instead of running on.

That figure corrects the mental picture most people have. A perm does not take your hair apart and rebuild it. At its strongest it opens something like a quarter of the bonds in the fibre, and the other three quarters are what keeps the hair on your head while the rod does its work.

Resistant hair, grey hair, and the heads it is wrong for

The alkaline perm survives every gentler invention because nothing else opens a tight, flat, unprocessed cuticle. If you have thick, coarse, glassy virgin hair — the kind that slides out of a set by lunchtime — this is likely the only chemistry that will hold the shape you asked for. A softer lotion on that hair does not give a softer curl. It gives no curl, and a bill.

Grey and white hair

Grey hair usually lands here, and for a reason clients find counter-intuitive. Unpigmented hair is often resistant rather than fragile: the cuticle tends to lie tight and flat and the fibre can be coarser than the hair it replaced. It is a candidate for the strongest lotion in the room, not the weakest, provided it passes the elasticity test like anything else. More at perms and scalp health.

On single-process tint it is technically possible and usually the wrong call: the swelling fades and muddies the colour you paid for. An acid-balanced perm does the same job on tinted hair without that argument.

What the service actually involves

1. Elasticity test first. A wet strand is stretched and released. If it stretches far and does not come back, nothing later in this list matters. This is the step that should end some appointments, and occasionally does.
2. Do not scrub your scalp for two days beforehand. This is the one piece of preparation nobody tells clients. A pH 9.5 lotion on a freshly abraded scalp stings and can burn. Wash gently, or not at all, in the 48 hours before.
3. A gentle clarifying wash. Surface product comes off; the scalp is not massaged hard.
4. The wind, thirty to forty-five minutes. The rods author the shape, so this is where the result is decided — see rods: size vs shape.
5. Lotion on, roughly fifteen to twenty-five minutes of processing. The ammonia is unmistakable. Timing is watched on a test curl, not on a clock alone: the stylist unwinds a rod part-way and looks at whether the S has formed to the diameter of the rod.
6. The long rinse. Five to ten minutes of warm water, to flush the alkalinity out before an acidic neutraliser meets it.
7. Blotting, then neutralising. Every rod is blotted properly, because water left in the wrap dilutes the oxidiser. Then the neutraliser goes on and the bonds close in their new positions.

When the first test curl should be taken is a genuine disagreement between manufacturers — current professional systems specify anything from two minutes to ten, and one says none is needed. Your stylist follows the instruction for the product in their hand; anyone quoting a universal number is quoting nothing.

Over-processing, and how to recognise it in your own hands

The failure mode of an alkaline perm is not that it does too little but that it does too much, and unlike almost everything else in a salon it cannot be corrected. Colour can be re-toned. A bad cut grows. Over-processing is structural, and the only real remedy is scissors.

What has happened is straightforward once you know where the reaction stops. Past the point the buffer damps it at, the lotion is no longer opening disulphide bonds selectively — it is degrading the keratin around them, so the fibre loses the scaffolding that lets it hold any shape at all, including the one it was born with.

The diagnostic

You can do this at the basin yourself, and it tells you what no mirror will. Take a wet strand and pull it gently between two fingers.

Frizz and over-processing are not the same problem. Frizz on a sound curl is dehydration and is fixable. Hair that stretches and stays is not.

Which is why the elasticity test is not a formality and the test curl is not either. A stylist who takes a curl down early and looks at it is buying information; one working from the clock alone is guessing on your behalf. The elasticity test is the whole of the defence, and it costs two minutes.

How long it lasts, and the first three days

Longer than anything else. Six months and beyond on the treated lengths, and in truth an alkaline perm does not really drop out at all — it softens a little and then stays. You do not wait for it to go; you grow it out and cut the permed ends off, living meanwhile with a visible line where the new straight hair meets the curl. Hair grows about half an inch, a little over a centimetre, a month, so that line is a real planning question rather than a detail.

That permanence is the trade. The cuticle does not lie quite as flat afterwards, so the hair reads drier and rougher than it used to, permanently. Sulphate-free washing, weight in the conditioner, no brushing when dry — a dry brush turns a defined curl into a cloud in one pass. Conditioning covers the routine.

Permed hair is more porous than it was, and London water is hard, so a chelating shampoo every three or four weeks keeps calcium from stiffening the curl. More in curl memory and water.

Where it sits against the gentler chemistries

Every perm chemistry sits on one ladder, and the ladder has no free end: gentler always means less durable. The alkaline perm is at the top of it.

Read that table one way and it is a menu of increasing kindness; read it the other way and it is a schedule of what you give up. The right lotion is the mildest one that will hold the shape you asked for on the hair you have.

You will also meet this chemistry in almost every home kit ever sold, which is most of why home perms have the reputation they do — see the home perm boom. Among professional lines it is the declared basis of Zotos Design Freedom and the firm end of Quantum, and where L'Oréal Professionnel Dulcia Advanced, Wella Perform+ and Schwarzkopf Natural Styling put their resistant-hair options. Read the active ingredient, never the range name.

Questions