How Heat Affects COLOURED Hair...

Light hair colour? Extra careful with the heat!

It's no secret that excessive heat can leave all all hair types looking worse for wear. But research shows that heat can cast some hair colours in a much more unflattering light than others.

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When it comes to imbuing your hair with colour, a rainbow palette is at your fingertips, thanks to the technological advances that have seen shade options increase exponentially in recent decades. Even if you start off with the naturally deep tones that characterise the hair on the heads of 80% of the world's women, you can go through a range of browns, reds, and blondes, all the way to platinum, not to mention colours that never naturally occur in human hair. Today's heat styling options, too, are amazing: you can get your hair slippery-smooth with a blowout, seal the slinkiest ringlets into place with a curling iron, or thermally set your hair into a sea of waves. But while you're spoiled for choice with ways to heatstyle, be careful not to go overboard or your hair colour might have to pay the cost.

It turns out that some of the discolouration which can affect coloured and naturally white/grey hair, a problem often blamed on a host of other culprits like bad dye jobs, porosity issues, deposits from products and even pollution, might sometimes be due to heat styling.

While all textures and tones of hair should be wary of overdosing on heat, due to the damage that it can cause, it turns out that light-coloured hair has a particular vulnerability. If your hair is light – whether a natural silver, bottle blonde or sunkissed gold – then it turns out that even slight exposure to heat can harm your hair colour, stamping it with an unsightly yellowing effect.

Studies carried out in the US have found that exposing the hair to 164 degrees Celsius heat – a temperature which many flat irons and curling irons easily exceed – can cause light-coloured hair to gain an undesirable yellow tinge in as little as 2 minutes. What's more, using the iron for 30 minutes (that includes the cumulative effects of using the iron in short intervals of only a few seconds at a time) caused even more dramatic colour changes. While white, and naturally pale blond hair both yellowed, bleached hair yellowed, too – then turned dark brown or even black! Darker hair showed only a slight colour change.

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The yellowing effect is attributed to the breakdown of the regions of the hair shaft responsible for its colour. Scientists also think that the dark colour formation in bleached hair is likely due to melanin fragments, which remain as residue in the hair after bleaching with hydrogen peroxide. Though too big to be rinsed from the strand, they are usually too insignificant to affect hair colour under normal circumstances. Under high heat, however, the decomposed bits of melanin clump together, reforming the pigment and creating streaky, dark colour in the hair. If your hair is naturally dark, but you're currently rocking even light brown hair, remember that it took some bleach to get your hair to that colour – even if you didn't go all the way to platinum – so your hair is similarly vulnerable.

To protect your hair from this heat, the first thing you need to do is turn the dial down! Hair actually starts to get damaged at temperatures well below 164 °C – it's just that the damage really becomes evident in terms of colour from that point on. And while it might be tempting to forego heat protectants if you have resistant hair, depriving your hair of that final barrier could eventually make it so weak it can no longer stand up to heat styling at all, not to mention destroying the colour you invested hours – and £££s – in the stylist's chair to get. Using a good heat protective conditioner and serum before any heat tools touch your hair is a must, but the heat itself still needs to be applied wisely. So if you love your colour – whether salon-infused or instilled by nature – to keep it vibrant, keep your irons at the lowest temperature possible.

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