By week eight at the bowl, we can tell the difference between fade and dullness, the two things most clients lump together when they ask about hard water hair colour fading. Fade is the colour easing into a softer version of itself, which is what a good toner is built to allow. Dullness is something else. It is the cast a client gets when minerals and chlorine sit on the cuticle and refuse to leave.

The question we hear most often, from new clients and from women who have moved up to the south side from elsewhere, is whether Glasgow water is the reason. The answer is more interesting than yes or no.

Glasgow water, settled

Glasgow water is famously soft. The supply has come from Loch Katrine, thirty miles north in the Trossachs, since 1859, treated at Milngavie and pulled south by gravity. There is no chalk and no limestone in the headwaters. The calcium and magnesium readings sit at the bottom end of the scale.

On the United States Geological Survey scale, Glasgow falls inside the soft band, well under sixty milligrams per litre of calcium carbonate. For comparison, much of the south-east of England runs above two hundred. That is genuinely a quiet gift for colour-treated hair, and the clients we see who have moved up from London or the Cotswolds usually notice the difference within a few washes.

So when a client says, the colour fades faster up here, the answer is no, it doesn't. The fade is slower. Something else is going on.

What minerals do to a colour-treated cuticle

Even in soft water, traces of metal still come through the pipes. Iron and copper are the ones we watch. They carry a positive charge. Hair carries a negative charge. They bind to the cortex through a lifted cuticle, particularly after a hot shower, and they sit there.

Copper is the one that misbehaves with colour. It oxidises in the cortex, which is why a lightened head can drift toward a green cast after a fortnight in a chlorinated pool. Iron darkens and dulls, pushing reds and browns toward something muddier. Neither effect is fade. Neither will lift with an ordinary shampoo.

What the client sees at home is the difference between the cool ash that walked out of the chair and a warmer, duller version eight weeks on. Light catches differently. The toner has not failed. The cuticle is loaded.

The dullness Glasgow clients still describe at week ten

If the water is soft, the question is where the dullness is coming from. In our experience at the bowl, three places.

We have been watching this same pattern from the chair since 1997. The address has changed, but the cuticle hasn't.

Chelating shampoo, and when we reach for it

A chelating shampoo, sometimes written as a clarifying shampoo, contains an agent (most commonly a form of EDTA, or a citrate) that binds to metal ions and lifts them out of the cuticle. It is not a replacement for a hydrating shampoo, and it is not meant for everyday use.

We use one at the chair before any colour correction, almost without exception. At home, we suggest one wash every four to six weeks for a colour client who swims, who travels, or who lives in a tenement with original copper pipework. More often than that and you will dry the lengths faster than the toner can keep up.

The order matters. Chelate first. Then a deep conditioning at the bowl, or a long mask at home with heat. The cuticle is at its most open and accepting in that small window after the cleanse.

The travelling client

A familiar story. A client back from a long stretch abroad. The colour was right on the day they left. Six weeks of hotel showers, harder local water, pool chlorine and a fortnight of salt swimming have undone the finish.

The placement is intact. A balayage we hand-painted at the chair still sits where it was put: soft through the canopy, weighted at the ends, growing out the way it was meant to. The cast is wrong, that is all.

Eighty per cent of that walks out under a chelating cleanse, a glaze and a long bowl treatment. We do not need to recolour. We need to clean what is sitting on the cortex.

What we do at the bowl

Two passes, usually.

The first is a chelating cleanse: gentle massage at the roots, then through the length and ends. Two minutes. Rinsed cool. The second is a deep conditioning, sometimes a bond-repair mask if the lengths are tired but otherwise sound, sometimes something heavier if the cuticle has been pushed harder. Which we reach for is a protein or moisture reading, taken in the hand at the bowl before any product goes on.

If the client is travelling again soon, we will often finish with a keratin blowdry treatment, because a flat cuticle holds toner and resists metal pickup better than anything else in the kit. It buys roughly twelve weeks of cleaner finish.

Looking after the fade between visits

The chair you only leave when the work is right.

There are small choices that buy a colour client an extra fortnight of finish at home.

Before you book

If a colour walked out right and now looks wrong, that is almost always a cuticle problem, not a placement problem. The first hour of a consultation will usually tell us which one we are looking at, and what the bowl can put right before any further colour goes on.

Endz Hair Boutique works one guest at a time, by appointment, on Paisley Road West. If a chelating wash before your next colour visit is what is needed, we will do that at the bowl first, then look at where the colour wants to go next.