The Element
Summer 2022
The chemistry behind hair dye The concept of being able to change hair colour is fascinating, and there are many different types of ways to do it. Foremost, the molecules that cause our hair to be coloured in the first place are pigments called melanin or more specifically, eumelanin and pheomelanin. Eumelanin is the pigment in charge of brown and black shades and pheomelanin gives blonde to red shades. This means that darker hair contains more eumelanin (the more abundant type) and lighter hair colours contain primarily pheomelanin. Different shades of hair colour simply depends on the ratio of concentrations of the two pigments.
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Temporary hair dye is quite popular for those who want a short term change. It does not actually change the natural hair colour as the dye does not penetrate the cuticle at all, it merely attaches itself to it, meaning that they don’t damage the hair at all. This means that after a certain amount of time, the colour will be washed out as the hair is washed. However, these conditions also means that temporary hair dye is not effective on people with naturally dark hair as the dye on the cuticle does not show. Common examples of temporary hair dye are hair colour sprays and hair chalk; these both wash out in one wash meaning they are very short term.
The hair is structured as concentric cylinders made up of three layers. The outer layer is the cuticle which is transparent and protects the cortex, made up of lots of overlapping dead cells. The middle layer is the cortex, which provides the strength, moisture, colour and texture to the hair (melanin is found in the cortex) and the inner layer is the medulla, which is the core of the hair and may be absent in some cases. Now that we know a little about the chemistry of natural hair, we can talk more about dyeing them. As many will know, there are different ways to change the colour of your hair, ranging from temporary dye to permanent dye.
Semi-permanent hair dyes are perfect for those who wish to have a longer lasting change and they’re also great for grey hair coverage. They penetrate the cuticle without reaching the cortex and covering the natural pigments (this could be a downside as it limits the colour palette meaning those with darker hair may find it difficult to work with this type of dye). They do not damage the hair structure at all which is a bonus but the colour fades and disappears after usually four to six weeks.
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