Curl Memory and Water

The difference you are actually paying for

Curl memory gets described as a mystical property some hair has and some does not. It is mechanics: the elasticity of the cortex, the geometry the fibre grew with, and how completely the cross-links were rebuilt at the end of the service.

Wind hair round a rod and the chains on the outside of the curve stretch while those on the inside compress. What happens next depends on which kind of bond is doing the accommodating.

One changes what your hair is doing today. The other changes what it does by default. That, and not longevity, is the honest argument for a perm over a wand.

Natural curl is architecture, not humidity

A piece of trade folklore worth correcting, because it leads people to wrong conclusions about their own hair: the idea that naturally curly hair holds its shape effortlessly through hydrogen bonding and moisture.

It does not. Straight hair grows from a round, symmetrical follicle; wavy and curly hair from an oval or curved one, which lays keratin down asymmetrically across the fibre as it forms — different cell types on one side of the shaft from the other, all the way down. That asymmetry is built into the cortex during growth. It is structural and permanent for the life of that hair.

Hydrogen bonding explains why curly hair responds to humidity from one day to the next. It is not why the hair is curly. And the distinction matters commercially as well as technically, because it tells you exactly what a perm is being asked to do: manufacture, through reduction and oxidation, an asymmetry that a curly follicle produces for free.

It is also why a chemical curl is more maintenance than a natural one of the same tightness. The perm works against the fibre’s original architecture every day. The natural curl is the architecture.

Three reasons a curl lets go

The three have different fixes, so it is worth establishing which one happened before booking anything else. Dilution is a stylist problem. Rod diameter is a design problem. An absent sulphur atom is not a problem at all — it is a refusal that should have happened at the consultation.

London water, and what it does over months

London sits on some of the hardest water in the country, and a client permed here will be washing it at home in that water for the next six months. It is the slowest and least visible thing that shortens a perm, and the one nobody suspects.

Hard water carries multivalent cations in solution — principally calcium and magnesium, with iron and copper alongside. Over time they deposit under the overlapping scales of the cuticle and bind to the keratin. The part that matters: chemically treated hair binds more mineral than untreated hair does. A perm raises porosity and leaves more sites for mineral to attach to, so the hair most affected is exactly the hair that has just been permed or coloured.

The effect is cumulative rather than dramatic. Over months it reads as dullness and a stiff, coated handle — the surface stops reflecting light and the curl loses its spring. On a tight coil that is a nuisance. On a soft wave it is fatal: a shallow bend has little structural memory to spare, and mineral weight pulls it flat.

Swimmers are a separate and more serious case. Regular chlorine exposure alongside pool copper does measurable oxidative damage over months — raised porosity, reduced elasticity, faster lotion uptake than expected — and is a strand-test case before any perm. Someone who merely washes in London tap water has a hard-water problem, not a chlorine problem, and the two need different pre-treatments.

What a chelating shampoo can and cannot do

Two products get used interchangeably and are not interchangeable.

1. Clarifying shampoos are high-detergent formulas that strip surface oils, silicones and particulate build-up. They address product residue. They do not remove bound minerals, and repeating one will not change that.
2. Chelating treatments use agents such as EDTA or citric-acid formulations that bind metal ions into a water-soluble complex which rinses away. That is what addresses hard-water loading, and why a chelating wash before a perm on a white or blonde head is not optional.

Both work at the surface and on cuticle-bound mineral. Neither comprehensively clears the cortex.

That qualification is regularly overstated on packaging. A client with years of hard-water accumulation is improved by chelation, not reset by it, and the perm should be planned on that basis. Practically: a filtered showerhead and a chelating shampoo used periodically are what keep a perm looking like itself in month four.

One instruction that does not change: the hair is clarified before a perm, the scalp is not scrubbed — see perms and scalp health.

Every method claimed to remove a perm, assessed

When a client tires of a wave the internet supplies a great many answers. Most are wrong, and it is worth being blunt about which.

The two that need more than a row

Thio straightening — Japanese thermal straightening, rebonding — is real. A strong thioglycolate reducer with flat-ironing under heat breaks the curl bonds and rebuilds them straight, and it does change the shape permanently. Over already permed hair, though, it is a second full restructuring of a fibre that has had one, and where porosity is raised the overlap breaks the fibre down. Specialist work with a real failure rate, not a routine fix; the limits are on the straightening guide. A hydroxide relaxer over a perm is not a lesser version of that but a prohibition: lanthionisation, one sulphur permanently gone, no route back. See perm versus relaxer.

Keratin and Brazilian smoothing are sold as reversals and are not. They alter no internal bond; they coat the cuticle and fill the gaps chemical processing left, which weights a soft wave down and removes frizz. It looks like loosening. It is coating, and as it wears off over the following months the permed pattern comes back exactly as it was — a mask, not a reversal, worth having only if you know that is what you are buying.

As for oils, masks and detox washes: no conditioner shifts a covalent bond once a neutraliser has locked it. Deep conditioning is genuinely valuable on permed hair for moisture and slip, and it will make a perm look better. It has no effect whatever on the geometry of the cortex. Once a length of hair is permed, that length is permed for the rest of its life.

If the perm is too tight, something can be done

Everything above describes a perm somebody has lived with and tired of. A fresh perm that has come out tighter than asked for is a different situation, and the honest answer is not “nothing can be done”.

Prompt re-processing. A mild reducing agent is applied again — on a much larger rod, or with no rod at all — and re-neutralised, relaxing the curl by partially breaking and re-setting the bonds just formed. It works only within a short window after the service, only on hair that had the strength for the first perm, and only in experienced hands, because it is a second chemical process on hair that has just had one.

Two things not to do meanwhile. Do not fight it daily with a flat iron — permed hair has raised porosity and a compromised cuticle, and repeated high heat produces scorching and breakage faster than the perm ever did. And do not have a large-rod wave put over the top: that is the same reduction chemistry on oversized rods, which makes it another perm rather than a correction.

Through a grow-out

Removing a perm entirely means growing it out and cutting the permed ends away progressively. Hair grows about half an inch, a little over a centimetre, a month, so on long hair that is many months to a couple of years. Through it you manage two textures with a transition line where they meet, and that line is where hair snaps. A heavy multi-row styling brush catches and breaks it exactly there. Wide-tooth combs, conditioner on the lengths, and a haircut that keeps the line out of tension.

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