Eliminating brassy yellow tones from blonde hair is an ongoing mission for most blondes. Help is at hand at home, however, and it’s all about the colour purple. Purple shampoo, which tones out brassiness, is essential for maintaining a cooler, creamy blonde, but what is it that makes a great toning purple shampoo - and why is it purple?
How does purple shampoo neutralise brassy tones?
When you shampoo your hair with a purple shampoo, like normal shampoos it will work on the pH of the hair and the slight alkalinity will open up the hair shaft cuticle slightly. When this occurs, pollutants, dirt and excessive oil are removed. A purple shampoo will deposit a small amount of violet pigment into the outer cuticle where it remains until you shampoo your hair again. It is this deposit of colour that creates a visually neutralising effect for brassy and yellow tones in your blonde hair.
Why does blonde hair need purple shampoo?
It all comes down to the basics that we learned in art lessons at school: the law of colour is that opposite colours neutralise each other. So if you see yellow in your locks, the opposing colour is violet. Blonde shampoos contain purple pigment that will make your blonde hair look cleaner and banish the brass, so you look like you have just stepped out of the salon.
How often do I use purple shampoo?
Every blonde is different. If your hair is dry or is very pale platinum blonde, once a week should be ample as it will only take a small amount of pigment to neutralise yellow tones. If you wash your hair frequently, using a purple shampoo more than twice a week will result in a build-up, giving your hair a dull purple 'glow'. The goal is to neutralise the yellow without making your blonde hair look dull or over-toned. If your hair is in exceptionally poor condition, mix a small amount of purple shampoo into your normal shampoo to dilute the pigment, and focus on the roots and mid-lengths - the ends will be more sensitised and therefore more likely to grab the purple tone.
Why should you carry out an allergy test before using purple shampoo?
There are a broad range of purple shampoos available on the market. Depending on which colour pigment is used, it is advisable to do a small patch test 48 hours before using the shampoo. It is unusual to have a reaction to a toning shampoo, but some individuals are extremely sensitive to colour pigment - even temporary ones - so it is best to do a quick test. Dab a very small amount behind your ear and leave it to dry. If you experience any itchiness or discomfort, refrain from using the shampoo.