What are purple hair care products?
A purple shampoo or conditioner, if you’ve never used one, is simply a cleansing or hydrating formula spiked with purple pigments. Why purple? If you’ve ever taken an art class, you’re probably familiar with the color wheel. If you haven’t, you can check it out here. One thing art students (and professional colorists) learn early on is that hues on opposite sides of the color wheel are capable of canceling out one another. And purple is directly across from (you guessed it) yellow. Thus, applying purple pigment to lightened hair can instantly tone down unwanted (yellow) brassiness.
How purple shampoo and purple conditioner work
Unlike permanent, demi or semi-permanent dyes, the purple pigment you find in a shampoo or conditioner is temporary color. This means it will begin to wash out the next time you use a non-purple shampoo or conditioner—though using non-stripping, sulfate-free shampoos like those created by Prose will extend its longevity. Using purple hair care should also never turn your hair violet, but leaving it on for an extended period of time (more than ten minutes at a time) or using a purple product very frequently (more than three or four times a week) could potentially impart a lavender tinge, especially if your hair is very light (e.g. silver or platinum). If you do notice your locks are developing a lavender cast, simply scale back on usage of your purple product.
Why purple conditioner is your best bet for anti-brass
A purple conditioner is typically the more goof-proof option. Thanks to the rich, hydrating ingredients in a conditioning formula, the purple pigment is slightly softened (read: diluted), making you less apt to overdose, even if you leave the product on for more than five minutes or use it every time you shampoo.
One note: Natural blondes can also benefit from using a purple shampoo or conditioner once a week, or as needed. Although they need not worry about shampoo stripping color molecules from their hair, their light locks are still susceptible to discoloration from the sun, swimming in chlorinated water or washing in hard water. As for monochromatic brunettes or the raven-haired? Purple products won’t hurt your hair color, but, unless you have lighter streaks you want to brighten, they also won’t do much to enhance it.