pH is a measure of how acidic or alkaline a water solution is. A pH scale expresses exactly that in the form of a number from 0-14. 7 is the neutral point, anything below 7 is an acid, (with 0 being the strongest, like battery acid), and anything above 7 is alkaline. In hair colour, the pH level determines how permanent a change will be, and how fast the reaction will happen. An alkaline hair colour causes the hair cuticle to swell and open, which allows colour actives and dyes to enter deeper into the hair shaft. The oxidative chemical reaction is powerful and fast, allowing for bigger shade transformations, such as lightening, grey coverage and intense colour. However, in an acidic colour, the oxidative reaction is significantly slowed down, so the cuticle swelling is gentler, and the opening is smaller. This means it will not lighten the natural hair* but will give you a deposit-only colour with reduced or even zero damage.
As you can see above, both acidic and alkaline hair colours have their own unique benefits and qualities, meaning they’re each essential to your salon portfolio. Which one you use all depends on the result your client craves. If a dramatic colour transformation is their goal, an alkaline formula will help them achieve the intensity and/or lift they’re looking for. Traditional demi-permanent and permanent toners are formulated in this way, and they each have differing levels of alkalinity. Meanwhile, if your client wants a subtler result that will not lighten the hair, and preserves its natural character, a deposit-only acidic hair colour will achieve their dream result. However, for a long-lasting result they should opt for Shinefinity, with balanced pH technology, which gives them the best of both acidic and alkaline solutions.