Semi, demi or permanent: what those colour words actually mean

Semi permanent coats the outside of your hair and washes out in six to eight shampoos. Demi permanent sits just under the surface and fades over about 24 washes. Permanent opens the hair and swaps the colour inside it, so it grows out rather than washing out. Which one you need comes down to how much change you want and whether you are covering grey.

The short version

Semi permanent coats the hair and washes out in 6 to 8 shampoos.

Demi permanent uses low peroxide, blends grey, fades over roughly 24 washes.

Permanent lifts and deposits, covers grey fully, grows out with a root line.

Only permanent colour can make your hair lighter than it is now.

Patch test 48 hours before, every time, for any of the three.

Semi permanent, the one that sits on top

Semi permanent has no ammonia and no peroxide in it. The colour molecules are large, they cling to the outside of the hair shaft, and every wash takes a few of them with it. Six to eight shampoos and it is gone.

That means it cannot lighten anything. If your hair is a level 5 brown, semi permanent will only ever take you darker or add a tone on top. Put a copper semi on dark brown hair and you will see a warm shift in the sun and not much else.

It is the safest thing we can do to hair that has been through a lot. No lift, no swelling of the cuticle, nothing that weakens the strand. I use it on clients who want to try a colour before committing to it, and on hair that is already fragile from bleach.

It will not cover grey properly either. Grey hair has no pigment and a smooth, resistant cuticle, so a semi tends to stain it a lighter, brighter version of the shade and wash out of it first. You get a few weeks of blended grey, then it comes back.

Demi permanent, the middle ground

Demi permanent is mixed with a low volume peroxide, usually 5 to 10 volume. That is just enough to lift the cuticle slightly and let smaller colour molecules sit underneath it, without touching your natural pigment.

The result lasts around 24 washes and fades softly rather than dropping off a cliff. There is no hard regrowth line. When it goes, it goes gradually, which suits people who are not sure they want to be tied to a six week colour appointment forever.

Demi will blend grey rather than block it out. If you are 20 or 30 percent grey, a demi will knock the brightness out of it and make it read as a highlight instead of a stripe. Past about half grey, it will not hold.

Every toner on our price list is a demi permanent. That is what a toner is. It is why toning fades, and why we tell you to come back for a refresh rather than acting like it is permanent.

Permanent, the one that changes the hair itself

Permanent colour is two things working together. Ammonia, or an ammonia substitute, opens the cuticle. A higher volume peroxide, usually 20 to 40, removes some of your natural pigment while the new colour develops inside the cortex.

That is the only way to go lighter with tint. Everything else deposits. It is also the only category that gives you full, opaque grey coverage, because it puts pigment inside a hair that had none.

The trade off is that it does not wash out. It grows out. Half an inch a month, and by week six or seven you have a visible line where your own colour starts. That is not damage or a bad application, that is just hair growing.

Permanent also does the most to the structure of the hair. Not enough to worry about on healthy hair done properly, but it stacks. Six years of full head tint every six weeks is a lot of peroxide sitting on your ends, which is why we move most long term clients onto a root tint and leave the lengths alone.

Semi, demi or permanent hair colour: which one you actually need

Under 30 percent grey and you want richness or a tone: demi. Trying a colour you are not sure about, or working with hair that is already compromised: semi. Covering grey properly, or going lighter than you are now: permanent.

The other thing that decides it is your maintenance appetite. Permanent means a root appointment every six to eight weeks, for good. Demi means a top up when you feel like it and no penalty if you leave it three months. I would rather you pick honestly than pick the one that sounds best while you are sat in the chair.

Whichever one you go for, we patch test 48 hours before. A reaction to hair dye is an allergic contact dermatitis, and it can take hours or days to show, which is exactly why the test is not done on the day. We do it every time, even if you have been coming for years, because sensitivities develop.

What it costs and how long it takes

Full tint is £50 to £55 and root tint is £40 to £47. A toner is £35 to £40 on its own, or £20 added onto another service. A tint surround, which is colouring around a foil to take out the last of the grey, is £20. Everything is on our pricing list.

Root tint is about 45 minutes of processing plus your cut and finish. A full head tint runs closer to an hour and a half all in. Toners are quick, around 20 minutes on the backwash and you are done.

If you are not sure which of the three you want, book a consultation rather than guessing. We are at Shop 660, Jansel House, Hitchin Rd, Stopsley, Luton LU2 7XH, open Tuesday and Wednesday 10 to 8, Thursday 10 to 6, Friday 10 to 3 and Saturday 10 to 4.30. Call 01582 730381 or book online. Klarna is there if you would rather spread the cost.