WH STAFFERS PUT DYES TO THE TEST - CHECK OUT THE BEFORE AND AFTER SHOTS

Nearly 80 per cent of Australian women dye their hair. And why not? Sure, it may just be 100,000-odd strands of dead cells, but your hair has a huge impact on how you look, how you feel - even how other people perceive you. (You know the cliches: fiery redhead, sensual brunette, gentlemen prefer blondes...) And it doesn't have to cost you much - if you do it at home. But how, exactly, does the dyeing process work, why does it smell so rank, and how can you make sure you go ash blonde, not Fozzie Bear orange? Read on for the answers...

Your hairs have three main layers: the outer is the cuticle, the middle's the cortex (where your hair pigmentation, melanin, is stored) and at the core is the medulla. There's dark and light pigment, and your colour is determined by the ratio in which they blend. "If you have a black or dark-brown mane, you have lots of the darker melanin called eumelanin; if you have blonde, ginger or red hair, you have more [lighter] phaeomelanin," says Tony Pearce, clinical director of National Trichology Services. And, those silver foxes out there - you have no melanin. It took till early this year for scientists to discover why hair loses melanin - our follicles produce hydrogen peroxide and, as we age, the peroxide builds up, removing melanin. Which brings us to dyeing...

Chemical reaction

Let's compare the outer layer of your hair shaft to a Vienetta: layer upon layer of tightly stacked protein tiles. "To change your hair's colour, you need to lift these upper layers to let the colour molecules sit inside the hair shaft," says Bronwyn Fraser, national education manager for L'Oréal Australia. To do this, you need hardcore chemicals -ones that make your eyes water. That strong hair-dye smell comes from the reaction with the sulphur in your hair. The most common chemicals in hair dyes are hydrogen peroxide and ammonia. "Hydrogen peroxide is used to break up colour inside your hair shaft," says Fraser. The higher the concentration, the more pigment is removed. Ammonia causes the hair shaft to soften and opens up the cuticle, allowing the colour in.

When these chemicals make strands expand, they put them through some trauma. You may notice your hair seems thicker post-dye job - that's because your hair cuticles have lifted, like a pine cone left in the sun. "If your hair's in good condition, it's possible to rectify the damage with treatments that seal down the cuticle," says Wayne Lewis, colour director at Sydney's Atlantis Hair. But if you colour your hair all the time, cuticles can become resistant to product and you'll get frizz - your hairs' way of telling you to stop colouring or go for the chop.

Think inside the box

Ask yourself how big a commitment you're willing to make. Then, pick a formula based on your comfort level:

Semi-permanent dye is like a summer fling - it vanishes after about 10 shampoos. Since semis don't contain peroxide or ammonia, they can't lighten your hair and the colour doesn't interact with your natural pigments, so they won't drastically transform your colour. They only deposit pigment, enhancing your current shade. The colour molecules are small so they eventually leave the hair shaft with washing.

Want something a bit more serious? Go with demi-permanent dye. These contain low levels of ammonia, helping colour stay in your hair longer, and fade over about 25 washes. A demi can take you a shade lighter or two shades darker. The pre-colour molecules penetrate the cuticle and enter the cortex where they create medium-sized colour molecules. Their larger size means they take longer to wash out.

Ready for a long-term colour change? You want a permanent dye. This alters your shade with peroxide and ammonia, so the colour will last until it grows out. "This product lightens the hair's natural pigment to form a new base, then adds a new permanent colour," says Fraser. This is the only choice for covering all greys.

Find the right hue

Pay attention to those tiny tufts of hair in hair-dye aisles. All colours are labelled from 1 to 10, with 1 being blonde and 10 being black. "Determine your current colour using these 10 base shades and look at the shades close to your number," says Fraser. For the most natural effect, stay within two to three shades of your natural colour. "When in doubt, start lighter," adds Steve Corthine, owner of Stevie English Hair in Sydney. "If the shade isn't right, it's easier to go darker than lighter."

Also consider undertones. Like your skin, your hair has them - either warm or cool - and the peroxide in permanent hair colour will expose them. "Brunettes tend to have warm undertones, which is why they're often surprised by how red their hair turns after colouring - especially when going lighter," says Belinda Jeffreys, Clairol Nice 'n Easy colour expert. If you're worried about your hair looking brassy, choose a cooler, ashier tone.

Another trick for forecasting how your hair will react to dye, says Corthine, is to look at your primary school pics. Levels of melanin decline as you age so, if your hair was a warm, honey blonde in kindy, there's a good chance it'll go warmer when you colour it now. And if you were a cool, ash blonde or brunette, dying or bleaching will probably reveal those undertones.

Ready...

You wouldn't slap paint on a cracked wall, right? So don't apply colour without conditioning. "If your hair is damaged, the pigment won't adhere well to your strands and it will end up looking streaky," says Judi Seeley, national technical manager at PPS Hairwear Australia. "At least one week before colouring, pamper your hair with a deep-conditioning treatment," says Frank Apostolopoulos from Melbourne's Biba Salon. This will create an even surface for the colour to attach to and help protect your hair from the dye's chemicals. And don't shampoo for a day or two before colouring. "Your hair's natural oils will protect your scalp and prevent irritation," says Apostolopoulos. It's fine to leave styling products in your hair - they won't affect the process.

Get set...

Colouring your hair is like baking a soufflé: if you don't pay attention to every step, you'll end up with a mess. Here, what to do before opening the box:

1. Ensure you have enough dye. "If you run short and the colour is sparse, the result will be patchy and uneven," says Hayley Mears, technical director for Brad Ngata Hair Direction in Sydney. So, long-haired girls, grab two packs.
   "Apply a thin layer of Vaseline along your hairline - from earlobe to earlobe and along your neckline - to prevent the dye from staining your skin," advises Corthine.
   Mist the ends of your hair with water. "Since the tips tend to be dry and damaged, they can soak up too much colour," says Keah Fitzgerald, Australia/NZ learning manager for Sebastian Professional. "Extra moisture will help colour go on more evenly and prevent the ends from getting darker than the roots."

Colour!

Divide your hair into quarters and apply colour one section at a time to make sure you don't miss a spot. Colour areas with greys first since they could use the extra time. If you're going darker, start from the top, front and ends of your hair, as these tend to be the lightest. If you're going lighter, start with the darker hair at the base of your scalp. If you're redoing the same colour: "Recolour the roots first and then cover the ends for just the last 10 minutes, as the peroxide in home dye is damaging on mid-lengths," says Fitzgerald. As soon as you've applied colour to the last strand, start a timer. Overdeveloping the dye could lead to dry, frizzy locks.

After dyeing, don't shampoo for two days. "This gives the cuticles time to close and seal in the colour molecules," says Fraser. And watch the water temp when you wash: "Hot water can cause cuticles to expand and open, allowing some of the colour to escape.

Help! Fix a dye disaster- click here.

Let us know: have you had a bad DIY experience? Or have you always been your own colourist?