The science of drying your hair
By a Cambridge academic who devotes his life to studying it
MY OWN hairline may be receding, but I can promise you this: a perfect blow dry is no accident. However, few people know there’s a scientifically proven technique which will give you the ultimate finish.
Indeed, it’s my job as a scientist to research how washing and styling can help, or harm, human hair — and from examining hair at the deepest cellular level, I’ve uncovered the secrets of attaining the perfect do.
For example, did you know that leaving your hair to dry naturally is more damaging than blow-drying it? or that going to bed with damp hair could be giving you split ends? So here’s my guide to the perfect way to dry your hair …
BUILDING BLOCKS
BEFORE you learn how to do the perfect blow dry, you need to understand some of the science behind your hair’s structure.
Hair is made from the protein keratin, the same substance as nails, feathers and claws. It’s a complicated structure; each shaft is like a rope within a rope.
There’s a protective outer layer known as the cuticle, which is calcified keratin, making it hard like fingernails. In the middle is the cortex, which is also made from keratin, but is more flexible as it’s not calcified. The cortex gives the hair its strength and elasticity.
We each have between 100,000 to 150,000 hairs on our heads. Asian hair is the thickest and strongest, measuring between 80 and 100 microns (a millionth of a metre) and is circular in diameter.
African hair is elliptical, or oval, and is also the thinnest at about 50 microns.
caucasian hair falls between the two; measuring between 50 and 80 microns and is slightly elliptical. on average, we lose 50 to 100 hairs every day.
NATURAL DISASTER
You might imagine that leaving your hair to dry naturally, without using a hairdryer, would be best for it. Wrong! This is possibly the most damaging thing you can do.
How? Well, it starts the moment you wet your hair. It changes the molecular structure of the strand straight away. When water is applied to hair, it is absorbed through the hard outer layer of cuticle into the cortex, which then swells up. This means it’s instantly weakened.
The cuticle acts a bit like roof tiles, with water going in between the gaps. Hair can absorb up to 30 per cent of its own weight in water. The longer it stays wet, the worse things get, as it continues to swell. This is because repeated swelling followed by slow drying of hair causes it to crack, permanently damaging the hair.
You’d be better off drying your locks quickly with heat, rather than going au naturel.
CHEAP PRODUCTS
We’ve looked at all sorts of shampoos and conditioners, from basic to high end, and despite what you might hope, the price did make a difference.
Fascinatingly, though, it was the most luxuriously expensive bottles that weren’t worth the price tag. once you start paying £30 or more, the results plateau.
But cheap products weren’t much good either. Instead, choose a mid-tier brand. And up to the £30 a bottle mark, the more you can spend, the better.
TOWEL DRY WITH CARE
You’re out of the shower and no doubt you’re in a rush to grab your hair dryer. But first, you must towel-dry your hair.
To do this, you should scrunch gently to remove excess water. Don’t rub. rubbing may break weakened hair, and the resulting different lengths of strand cause hair to look frizzy.
COMB WET HAIR
Don’T brush wet hair. use a wide-spaced comb, but never a brush, and go slowly to minimise damage. A brush may tear your water-weakened locks, causing instant breakage.
DRY BEFORE BED
You should never go to bed with damp hair, either. It may be tempting to save time and only half dry hair before bed, but this is a terrible mistake.
You might be causing irrever- sible damage, which could take months to grow out. If you move your head around in your sleep, the friction against the pillow could cause hair breakage. It’s the same if you leave the house with damp hair.
Your hair can also be affected by humidity in the environment, so it may rapidly become frizzy and dull — or suffer from the effects of pollution, with chemical particles causing damage and dryness.
LOW SPEED IS BEST
once you’ve towel dried and combed your hair through, turn on the hairdryer. use a low heat and speed setting at first. This is so the hair doesn’t overheat. You should dry your hair in sections. Ideally, holding the hairdryer 15cm from the head and dry with a continuous motion. As soon as hair starts to feel warm it will be about 90 per cent dry, and you can turn up the heat.
It’s vital that you don’t forget to give it a blast of cool air at the end. It makes a massive difference, ensuring the hair’s internal bonds are remade and sealing the style in place.
UPSIDE DOWN?
TURNING your head upside down does give volume, but it’s not necessary. volume is created by the hair strands coming out of the head at a higher angle.
So the best thing is to get the nozzle of the dryer as close to the scalp as possible to get lift.
Diffusers can help with curly hair, as they dry slowly and provide volume, lifting moisture out. The air circulates around the curls, defining them and minimising frizz.
NARROW NOZZLE
CREATING a shiny look is mostly down to aligning your strands of hair — ie making sure they point in the same direction.
To do this, section your hair and dry one at a time, aiming the dryer downwards as much as possible. This will blow out knots and tangles. ensure the nozzle of your dryer is narrow, as it makes an enormous difference.
ONLY TONG DRY HAIR
ONLY use straighteners or curling tongs on completely dry hair. Applying the heat of tongs to wet hair is catastrophic. As you heat water and turn it from liquid into gas, it expands. Water which is trapped in the cortex will burst out, causing damage.
If you’re trying to fix a style in place, use hair spray after drying and before straighteners.
TAME CURLY LOCKS
STRAIGHT hair is down to a round follicle, from which the hair emerges like a steel rod. Meanwhile, curly hair comes from an oval follicle. Despite what you might think, science proves it’s easy to dry curls, as described above, use a diffuser.
PERFECT WEATHER?
IT MIGHT sound bonkers, but the weather can affect your blow dry. It’s less about rain or shine, and more about the moisture in the air. If it’s humid, the style will drop more quickly. use a heat protective spray to reduce the effect of the humidity.
The ideal weather to achieve a perfect blow dry is a dry, cold, sunny day at zero degrees. Which is why your best hair days happen in the winter, not summer!
DR TIM MOORE holds a PhD in Microelectronics from Cambridge University and is chief technology officer at GHD Hair.