Crazy or cool? CLAIRE COLEMAN tries the new hair dye that changes colour with warmer weather

As I pass the hairdryer over my freshly dyed hair, I watch transfixed as the colour changes from boring brown to shimmering shades of blue and green — colours normally only seen on a magpie’s wing, or when petrol sits on a puddle. 

I turn the hairdryer to its cold setting and, just as swiftly, the colours disappear. Welcome to the new frontier in hair colour. Revolutionary technology that allows you to change shade in a heartbeat… and just as swiftly and painlessly switch back. 

It’s the brainchild of Lauren Bowker, founder of a company called The Unseen, whose other projects include sculptures that change colour when the wind blows on them and a collaboration with Swarovski that used 4,000 crystals on a skull cap that changed colour according to the wearer’s brain activity. 

As for colour-changing hair dye? ‘I had really long hair and was forever in the lab accidentally getting colours on me,’ Lauren recalls. 

Claire Coleman (pictured) tries The Unseen’s new hair dye Colour Alchemy, which changes colour with different temperatures 

That helped inspire her idea for a dye that changed hue with temperature. It debuted at London Fashion Week in 2017 and, within a week, a video showing hair ‘magically’ switch from black to red was viewed more than 80million times.

But it has taken five years to get it ready for home use. Now Colour Alchemy is about to be launched in five different colour-changing shades — and I am the first UK journalist to try it. 

It comes in a black jar wrapped in black paper, tied up with black string. I feel as if I had gone to a boutique in Harry Potter’s Diagon Alley and bought a spell to change your hair colour. 

The product itself looks like poster paint and is designed to be applied to dry hair as a single fine layer of colour — it’s good that you don’t need much, as it did make my hair feel a little stiff.

Fortunately, if you’re keen to experiment with fun colour but not so keen on showing off the results at work, it’s easy to brush or shampoo out. In fact, it’s almost more like make-up for your hair than traditional dye, since it only ever lasts for one wash. 

Another bonus? The dye takes almost instantly with no need to wait around. This makes it perfect for a party, and I predict that soon no festivalgoer’s beauty kit will be complete without it. 

Claire's favourite shade is Andrite, which gives her tips a deep magenta hue that goes green, blue and purple in the sun

Claire’s favourite shade is Andrite, which gives her tips a deep magenta hue that goes green, blue and purple in the sun

I start with a shade called Peacock — which is technically blue, but actually almost invisible when applied to my dark brown hair. 

But then I hold my hairdryer up to it and the magic starts. From nowhere, bright swirling colours appear. The colour change happens at relatively low temperatures — between 28c and 32c — so the natural warmth of your scalp or shoulders can be enough. A hairdryer, sunlight or even a warm breath can do it too, and a cool breeze is enough to reverse it, so it will literally change back and forth in front of your eyes. I play around with shades, trying them on different sections of hair. I put one named Borealis on my roots and watch it transform under the dryer from an inky purple to blue, green and pink. I give a strand around my face a dash of Phoenix and while the orangey-red shade is barely visible on my dark hair, as it warms up I see flashes of purple and yellow. 

My favourite is Andrite, which I use on the lighter tips of my hair to give them a deep magenta hue that goes green, blue and purple in the sun. It’s like the ends of my hair have been dipped in magic. So how does it work? Well, the particles in the dye act a bit like prisms that split light into a rainbow of colours. But the clever part is that they reflect different colours at different temperatures. 

Colour Alchemy, £66, available at Schwarzkopf Professional salons. It launches this month on the Unseen website (

Colour Alchemy, £66, available at Schwarzkopf Professional salons. It launches this month on the Unseen website (

‘Thermochromic technology [combining temperature and colour] is incorporated into a crystal formula that recreates the visual effect of a prism,’ says Lauren. 

‘Above a certain temperature, the active molecule in the dye undergoes a reaction and changes to one with a slightly different absorption of light, and thus a different colour.’ 

The current dyes can only be used on darker hair — black to dark blonde — because the technology requires a dark background to give a good depth of colour. 

At £66 for a 50g (2oz) pot, I guess you have to think of this as something more akin to a super high-end eyeshadow that you wear for special occasions, rather than your usual £5 home hair dye. 

And a little does go a long way. Lesley Jennison of Schwarzkopf Professional, the haircare brand that’s partnered with Bowker to bring the product to market, says doing your whole head could use up to half a jar, depending on the length of your hair. 

Or for a more economical but equally striking look, the dye can be used with a stencil to create a pattern. Or you could go for highlights or a freehand design.

‘A great tip for textured hair from wavy to super curly is to use a beauty sponge,’ she says. ‘Dip the rounded tip into the colour and run it along some strands on the top layers of your hair, concentrating around your face to frame it.’

Very little in the beauty industry these days is truly revolutionary, but this really is, and the potential for the technology to be applied to other areas, such as make-up, is really exciting. 

The Unseen already makes an eyeshadow that goes from black to silver in strong light. But one day — perhaps — we could also have bronzer or fake tan that intensifies in warm sunlight to give you more of a golden glow, or nail varnish that changes colour when you dive into a chilly sea. For now, if this is the modern take on the blue rinse, colour me happy.

  • Colour Alchemy, £66, available at Schwarzkopf Professional salons. It launches this month on the Unseen website (