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The science of hair dye: How it actually works

06 November 2019 | By Helen Clemson

Whether you’re a lover of DIY box dye or only entrust your colour treatments to your stylist, the science of hair dye starts with understanding the different types of colour processes available. 

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Industry experts refer to “levels” of colours: with semi-permanent (often known as a colour shampoo) being the least drastic look, demi-permanent being the next step up, and finally permanent colour being the longest-lasting option, generally requiring you to grow out the colour out over time.

 

Let’s start with the basics: What exactly is hair dye?

 

Let’s start off gently! The hair dye – if one can call it that – that is the least commitment is a semi-permanent, colour-wash, explains Shelene Shaer, hairstylist and co-owner of Tanaz Hair. “This adds to your existing colour, changing the tone of your hair not the level - in other words, no major colour change.” It does this with molecules so small they slip into hair follicle shaft and slip out again. “This type of colour lasts six to 10 shampoos and washes out,” explains Shaer. “Don’t expect it to cover grey, so use it only if don’t have any but would like to add more shine and life to your strands without the colour commitment.”

 

Where does demi-permanent colour fit in?

 

Next up is demi-permanent colour that may cover 50 percent of greys. “It won’t change the colour level drastically though. “With a slightly larger molecule it takes longer to shift out of the hair, as its low level of peroxide opens the hair cuticle slightly to deposit colour, which means it can blend up to half of grey hair,” explains Shaer. She suggests using this type of product if you’re starting to go grey and needing a colour treatment more than once or twice a year.

 

Should you go for permanent hair dye?

 

Finally, the dye that is going to take the longest to leave your locks – and that will need to actually grow out – permanent hair colour. With ingredients like ammonia, which forces its way into the hair’s cortex, and peroxide, it’s able give you a very noticeable colour change, whether you want to lighten or darken your natural pigment, explains Shaer. “This type of hair dye swells the hair cuticle and dries it out a little bit, so you will need to up the ante with great quality shampoos and conditioners to counteract this,” she adds.

 

IMAGE CREDIT: 123rf.com

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