How Hair Colour Works
THE SCIENCE OF HAIR COLOUR
To understand the science of hair colour, it is important first of all to understand WHAT we are colouring. Types of hair can be drastically different - from curly to straight, thin to thick and blonde to black - almost no two hair strands are alike. Knowing your hair type is very important when colouring your hair. For a basic overview of your hair’s make-up, take a look at our Hair Science article.
Once you know a bit about the make-up of your hair, it’s important to understand hair colour and how it affects your hair. Your natural hair pigment, called melanin, is housed in the cortex of your hair—which are the cells aligned along the hair fibre. This is why hair colouring also takes place in the cortex, since it affects the natural pigment of your hair.
Hair colouring works by coating each strand with colour (non-permanent colour) or by penetrating each hair cuticle, entering the hair cortex and bonding with the hair (permanent colour). While non-permanent hair colour can be shampooed out eventually, permanent colour, as the name suggests permanently colours the hair. However, since hair constantly grows, the colour will eventually grow out as new, uncoloured hair grows through.
Just as there are different types of hair, there are different types of hair colour, as identified in this chart.
Hair Colour Type
Amount of Time Colour Lasts
Lift Performance / Grey Coverage
Until hair grows out
Up to 3 shades lighter
Up to 100% grey coverage
Up to 24 washes
Very little lift
Blends away greys
Up to 8 washes
Blends away greys
HOW PERMANENT HAIR COLOUR WORKS
As the name suggests, this type of hair colour permanently colours your hair. It works from the outside in, penetrating each hair cuticle, entering the hair cortex and bonding with the hair. The process involves removing some or all of your natural colour and/or adding your desired colour with the product. While the colouring remains on your hair, your uncoloured hair at the roots will show through as your hair grows.
Here are some other facts about permanent hair colour:
- Offers 100% grey coverage, even on resistant greys
- Can lighten hair by 1-3 shades
- Can also be used for subtle colour changes
- Lasts longer than direct dye products
- Root application recommended every 4-6 weeks to avoid noticeable roots re-growth
HOW NON-PERMANENT HAIR COLOUR WORKS (UP TO 24 SHAMPOOS)
This type of hair colour works by coating each hair strand with colour. If you are colouring your hair for the first time or only want to enhance your natural colour, try a non-permanent product that lasts up to 24 shampoos and is close in shade to your natural or current hair colour.
Here are some other facts about non-permanent hair colour that lasts up to 24 shampoos:
- Lower pH than permanent colour
- No ammonia, uses ammonia substitute (MEA or AMP)
- Lower peroxide concentration than permanent colour
- Similar dye palette to permanents
- Leaves no noticeable root line
ANENT HAIR COLOUR WORKS (UP TO 8 SHAMPOOS)
Non-permanent hair colour that lasts up to 8 shampoos gently adds colour molecules to the cuticle layer of your hair. Lasting for 6-8 washes, each wash opens the cuticle—allowing colour to escape. It contains no ammonia or peroxide and offers no bleaching of your natural hair pigment.
Here are some other facts about non-permanent hair colour that lasts up to 8 shampoos:
- Colour is already formed in the tube—so you don’t have to mix anything
- It eventually washes out in 6-8 shampoos
- Contains no ammonia or peroxide
HOW CONDITIONERS WORK
Hair is almost constantly exposed to things that can cause damage: UV light, chlorinated water, saltwater, your diet, perms, heat styling. Even things like shampooing, towel drying and brushing cause friction, which can damage hair.
Once damaged, hair becomes rough and dull. Conditioners work to both protect against damage and repair past damage, leaving hair silky and shiny.
- Conditioners smooth the cuticle to restore smoothness
- They can also form a protective coating to prevent damage
- Many conditioners also have an ingredient that helps rebuild hair’s ability to retain moisture
FACTORS THAT AFFECT HOW HAIR COLOUR WORKS
Your current hair colour (natural or previously coloured) makes a difference in how non- permanent or permanent hair colour turns out. If you’re not sure what shade to choose, go with this longstanding hair colour rule: You can change your hair colour successfully up to three shades lighter or darker than your starting colour. If you currently have medium brown hair, for example, you could lighten it to a light brown or a dark blonde, or go darker to a dark brown.
Hair type also makes a difference. Coarse hairs, which are large in diameter, generally take more time to absorb colour, while fine hair, which is small in diameter, takes less time to absorb colour. Dry or permed hair may absorb colour more quickly. Since there are several factors that affect timing, it’s essential to use a strand test to estimate colouring time.
Now that you know how hair colour works, it’s time to colour!