How Temporary Hair colour works

Everyone thats ever used wash out hair dyes and chooses to switch up their hair colour relatively often will most likely have that one friend that tells you over and over that you're "ruining your hair" or that "one day all your hairs going to fall out".

The beauty of temporary hair colour is that in fact, we're not doing any damage to our hair at all!

A strand of hair is made up of three parts, the medulla, the cortex and the cuticle. The medulla is the very centre of the hair strand and is unaffected by hair dye so just ignore that bit! The cuticle is the outer layer of the hair strands, its made up of overlapping scales that open and close when products are applied to it. The Cortex is the area beneath the cuticle, this is where the hair colour pigments are found in the form of melanin proteins that give you your natural hair colour.

Permanent, semi permanent and temporary hair colours are all just pigment modules of various different sizes that stick to different parts of the hair strands.

Permanent colour is the only dye which creates a chemical reaction.

Permanent hair colour is made up of two parts, the colourant and the developer. The developer relaxes and opens the hair cuticle and allows the dye molecules to slip through into the cortex. It then removes your natural hair colour pigment usually with a chemical called ammonia (what gives dye its distinctive smell).

Then once the melanins natural colour pigments have gone, the tiny dye pigment molecules penetrate the hair cuticle and bond with the proteins in the cortex to take on the new colour. The new bonds formed within the cortex are what allow the colour to stay in the hair for several weeks, as the molecules are trapped inside the cortex.

Semi permanent hair dye molecules are bigger than permanent hair dye molecules but also relax the hair cuticle to slip through the scales and find their way to the cortex.

The difference, is that semi permanent dye does not react with the cortex chemically, it simply sticks to the outside of it; which is where it stays.

Heat can help to open up the hair cuticle which is why semi permanent colours are most vibrant when the hair is wrapped in plastic wrap during the developing time to keep the heat in the hair and to allow as many molecules through the cuticle as possible.

This is also why washing your hair with hot water will fade colour faster, as the semi permeant dye molecules will just slip back out of the hair cuticle every time the cuticle scales become opened.

Temporary hair dye works completely seperate to both of these other dye forms. When applied to the hair the temporary hair dye molecules are considerably too large to fit through the cuticle even when it is opened. They simply stick to the outside of the hair cuticle, coating the hair strand.

Because of how the temporary dye works on the hair, and its lack of reactions within the hair folical, you can rest assured that there is no means possibility for temporary colour to "ruin" hair! The pigment molecules stay separate to your natural colour and get washed away from the surface of your hair folical within a few washes.