The keratin blowdry sits in a quiet corner of our menu. It does not announce itself. It is the treatment a client comes back for in the winter, when the wind off the Clyde has roughened the cuticle, the highlights have done their work, and she wants the hair to fall the way it fell on the day she left the chair. That is what a keratin treatment is for. Not transformation. Not magic. A finish that lasts about twelve weeks, applied at the bowl, sealed with a single slow blow-through.
We are asked about it more than any other treatment on the list, and we are asked the same questions in roughly the same order. What does it actually do. Whether the formaldehyde stories are still true. Whether it suits dense hair, or fine hair, or curly hair, or coloured hair. How long it lasts. What to do about the first three days. This piece is the long answer, written the way we would explain it at the consultation if there were no kettle and no clock.
What keratin actually is, inside the hair
Hair is mostly keratin. Keratin is a protein, made up of amino acids (cysteine, lysine, arginine, tyrosine, and others) chained together and folded into long fibres. Those fibres twist into bundles. Those bundles make up the cortex of the shaft, the inner part that carries the colour and the strength.
Around the cortex sits the cuticle, which is keratin too, set in overlapping plates like roof tiles. A healthy shaft has those plates lying flat against each other. A damaged shaft has them lifted, broken, gappy. That is what frizz looks like under a microscope: a cuticle that no longer lies flat, scattering light instead of reflecting it.
Three kinds of bonds hold the keratin chains in place. Hydrogen bonds, the weakest, break and re-form every time the hair gets wet and dries. That is why a blow-dry sets a shape until the next wash. Salt bonds sit in the middle. Disulphide bonds are the strong ones; they hold the natural curl pattern, and they only break under chemistry (permanent waves, relaxers) or extreme heat. A keratin treatment does not touch the disulphide bonds. It does not change the curl pattern permanently. What it does, and we will come to this, is fill in the gaps and lay the cuticle back down flat.
What the treatment puts back, and where it sits
The keratin in salon treatments is hydrolysed. That is the key word. Hydrolysed means the long protein chains have been broken down into shorter pieces, peptides and amino acids, small enough to slip past the cuticle scales and reach the cortex underneath.
When we apply the treatment at the bowl, hydrolysed keratin coats every shaft from root to tip. Some of it sits on the surface, filling the lifted scales of the cuticle. Some of it works deeper, into the porous spots, the bleached zones, the places where colour has left the shaft thirsty. The effect builds in layers, surface and sub-surface, both.
What the client feels, the day they leave, is the cumulative result. A cuticle that lies flat. A shaft that reflects light evenly. A fall that swings instead of frizzes. The hair is not chemically different. It is more itself, with the gaps filled in.
The formaldehyde question, answered honestly
This is the question we hear at the consultation more than any other. The honest answer takes a minute.
Traditional Brazilian blowdries, the kind that came over from South America in the early 2000s, used formaldehyde, or compounds that released formaldehyde under heat (methylene glycol was the common one). The formaldehyde formed cross-links between the hydrolysed keratin and the natural keratin of the shaft. Those cross-links held the smoothing effect longer than anything that had come before. They also produced fumes that were rough on the lungs of the stylist and the client, particularly when activated under a hot flat iron.
The industry has moved on. Most modern keratin treatments, including the ones we use at Endz, replace formaldehyde with glyoxylic acid, glutaraldehyde, or carbocysteine. What these newer agents do, in plain terms, is form cross-links with the keratin chain that give a comparable smoothing effect without the airborne formaldehyde load. The chemistry is different from the old one, and the room is safer to work in. What we see at the chair is that the finish holds, and the air does not.
A formaldehyde-free treatment will not last quite as long as the old chemistry did. That is a fair trade. Twelve weeks instead of sixteen, in a room that is safe to breathe in. We will not go back.
Why we apply at the bowl, not on dry hair
A keratin treatment can be applied two ways. On dry, towel-dried hair at the chair, the method many faster salons use because it shortens the chair time. Or at the bowl, after a clarifying wash, while the cuticle is still slightly raised from the warm water. We do the second.
Here is why. The clarifying wash strips the day-to-day buildup off the shaft: silicones, hairspray, dry-shampoo residue, the film that ordinary shampoo leaves behind. With that gone, the keratin meets the shaft directly, not through a coat of last week. The warm water has lifted the cuticle scales slightly, which means more of the treatment penetrates the cortex rather than sitting on the surface.
A keratin applied on dry hair at the chair will still work. It will sit more on the surface, hold for a slightly shorter time, and the finish will be about smoothness rather than depth. We have done it both ways over the years. The bowl gives a more durable result. It is the difference between paint on a primed wall and paint on a dusty one.
The single blow-through that seals it
Once the treatment has been left to absorb, we rinse it gently, towel-dry, and begin the blow-through. Heat is the activating step. The hydrolysed keratin and the cross-linking agent need a temperature high enough to drive the bonding reaction to completion.
Our blow-through is done section by section, with a round brush and a moderate-heat dryer, sometimes finished with a low-temperature flat-iron pass where the hair needs it. Slowly. Once. That is the key. A rushed blow-through, finished before the chemistry has set, leaves an under-cured treatment that will not hold its full twelve weeks. A second hot pass over the top, sometimes used in faster salons to give the surface a glossier finish on the day, can flash-bake the cuticle and shorten the longevity. We prefer the single pass, slow and well.
It is the same principle we use across the rest of the work, on colour as on treatment. Slowness is not indulgence. It is technique. We have written about the same idea in the context of balayage on dark hair, where the painted lift only works if the brush has time to do its job.
Twelve weeks, and what holds them
The hold depends on three things. The chemistry of the treatment we use. The way it was applied at the chair. The way the client washes after.
The chemistry we have covered. The application we have covered. The home care matters more than most clients realise. Sulphate-based shampoos (the foamy ones) strip the keratin layer faster than gentler formulas. Sodium-chloride conditioners do the same. Washing daily shortens the hold by a few weeks. Washing two or three times a week, with a sulphate-free wash, gives the treatment its best chance. For clients whose hair is also colour-treated, the routine between visits takes a slightly different shape; we have written the wash and iron cadence for colour-treated hair in its own piece.
Twelve weeks is the figure we give. Some clients get a bit more, particularly those who heat-style sparingly and treat the hair gently. Some, particularly daily-foam-washers, get less. We tell people what to expect at the consultation rather than after the bill.
The chair you only leave when the work is right.
Who the treatment suits, and who it doesn't
The treatment suits hair that frizzes in humidity. Hair that has been coloured many times and lost its evenness. Hair that fights the blow-dry by midweek. Hair that has turned coarse at the ends. It suits dense Glasgow hair that wakes up the morning after a wash looking like it has been through a wind tunnel. It suits fine hair, too, though the finish there is more about silkiness than weight.
It does not suit hair that already lies flat and behaves. There is nothing to fix. We will say so at the consultation; we are not going to take a fee for a treatment that does no work.
It does not suit a client who wants permanent straightening. A keratin blowdry is not a relaxer. It softens texture and smooths cuticle. It does not change the curl pattern. If a client comes in with very tight curl wanting a poker-straight finish, we have a different conversation, and often a different recommendation.
If colour is also part of the picture, we will usually do that first and the keratin second. The order matters. There is more on the sequencing question in our piece on growing out hair colour, where the same principle of working with the hair's existing chemistry comes up.
Glasgow water, and what it does (or doesn't) to the hold
This is the section where we surprise people. Glasgow's water is soft. The bulk of it comes from Loch Katrine, about thirty-five miles north of the city in the Trossachs, fed by rainfall over granite and peat. That kind of catchment produces water with very low calcium and magnesium content. By the time it reaches your shower in Pollokshields or Hyndland or Shawlands, it carries none of the mineral load that troubles colour and treatments in the south of England.
This is good news for the keratin hold. Hard water (the kind they have in much of England) deposits minerals on the cuticle every time the hair gets wet. Over twelve weeks, that mineral film accumulates. It dulls the colour, it sits over the keratin coating, and it lifts the cuticle slightly with each wash cycle. In Glasgow we don't fight that battle. Clients who move here from London often notice that their colour holds longer, and their treatments do too. The water is doing them a quiet favour.
What we do see, occasionally, is product buildup. Silicones, dry shampoos, root sprays, leave-in conditioners that aren't quite the right formula: any of these can sit on the keratin layer over time and dull the finish. The fix is a gentle clarifying wash every fortnight or so. Not weekly, that would shorten the hold. A clarifier is a reset, not a routine.
The first seventy-two hours, and why they matter
For the first seventy-two hours after the treatment, the cross-link chemistry is still settling into the cuticle. The bonds have formed under the heat of the blow-through, but they have not fully cured. The hair is in a vulnerable window.
Tying the hair up, sleeping with a tight band, clipping it back behind an ear, tucking it behind a headphone strap: all of these can leave a kink or a flat patch that will be there for the full twelve weeks. We send clients home with this instruction. We say it twice, because the first time it tends to bounce off.
After three days, normal life resumes. Wash with a sulphate-free shampoo. Use a sodium-chloride-free conditioner. Heat-style as you like. The keratin will not lift off in the shower if the products are right. We keep a short list at the chair of the products we trust; we don't sell them, but we are happy to write the names down.
How the grow-out behaves, and when to come back
The grow-out is forgiving. There is no demarcation line, no hard regrowth band, because the treatment is a coating effect rather than a chemical change to the curl pattern. The new hair grows in with its own natural texture. The older shaft slowly loses its keratin layer over twelve weeks. The transition is gentle, a softening rather than a line.
Most of our clients come back for a refresh between weeks ten and fourteen. By that point the hold has started to soften. The frizz hasn't returned in full, but the shine has dulled by a degree, and the morning blow-dry takes a few minutes longer than it did. That is the signal to book.
If a client is also overdue a colour appointment (root, gloss, balayage refresh), we usually do the colour first and the keratin second. The treatment seals the freshly coloured cuticle, which extends colour longevity by a couple of washes and leaves the tone more even than it would be on its own.
We have written about that order of operations in more detail under hand-painted balayage, which covers the colourist's view of how a keratin sits over freshly painted highlights.
What the consultation looks like
We do not book a keratin blowdry without a consultation, even for clients we have known for years. The hair changes. The condition changes. The expectations need a five-minute conversation before the kettle goes on. We look at the cuticle, we look at the ends, we ask about the last few months of washing and styling, and we decide together whether the treatment is the right call for this visit. The same room and the same questions run on the colour side; we have set out what the first hour of a colour consultation covers in its own piece, for clients curious about the shape of that visit.
Sometimes the answer is no. The hair is in good condition, the fall is even, and there is no work for the treatment to do. Sometimes the answer is yes, but not yet: a deep conditioning at the bowl first, two or three appointments to rebuild the protein and the moisture balance, and the keratin in a month. Sometimes the answer is yes today.
The consultation is also the moment we walk through the rest of the menu, in case the keratin sits alongside a grey-blending colour plan or a longer balayage trajectory.
What twenty-eight years has taught us about this treatment
Nuzhat has been on the chair since 1997. That is twenty-eight years of watching new treatments arrive, get over-promised, settle into their proper place. The keratin blowdry has been through that cycle more thoroughly than most. It came in noisy. It went through the formaldehyde reckoning. It has come out the other side as a real, useful, well-understood piece of work.
What twenty-eight years on the chair teaches you about any treatment is the same thing. Apply it to hair that actually needs it. Apply it slowly. Be honest with the client about what it will and will not do. Send them home with the home-care plan in writing if you have to. Bring them back at the right interval, not at the most-money interval. The work earns the return.
The salon has been on Paisley Road West since 2020, by appointment, single guest at a time. If a keratin blowdry is something you have been thinking about, the consultation is where we map it out. Book an appointment, and we will have the kettle on by the time you arrive.