Why lightening hair with bleach is an art form and a science
When it comes to lightening hair with bleach there are numerous variables that a colourist must consider to achieve their client’s desired shade. These variables make bleaching hair both an art form and a science.
The Science: Natural hair colour pigment
Natural hair colour pigment, melanin, is produced within the germinal matrix of the hair bulb by cells called melanocytes. The melanocytes transfer melanin in small granules to the cortex of the hair shaft. These granules are associated with two types of melanin:
- Eumelanin – black and brown pigment granules
- Pheomelanin – red and yellow pigment granules
The proportions of these two types of melanin determines all natural hair colour. Typically, the less black/brown pigment that is present, the lighter the hair is. The more black/brown pigments that are present, the darker the hair is.
The Science: How bleach lightens hair colour pigment
Unlike colouring hair, where pigments are deposited into the hair shaft, bleach causes the natural melanin of the hair shaft to break down or dissolve. The process of bleaching the hair is called oxidisation.
In order to oxidise, bleach requires the addition of hydrogen peroxide. Once the two products have been mixed together they become an alkaline agent that initially soften the cuticle layers of the hair shaft. The softened cuticle layers then swell to allow the lightener to pass through.
Once inside the hair shaft, bleach begins to dissolve the hair’s melanin. Initially bleach dissolves the black and brown pigments which is relatively easy. It then dissolves the red and finally the yellow pigments. The lighter yellow toned pigments are much harder to dissolve.
This process is called lightening the underlying pigments of the hair. A lightening curve is an excellent way to visualise the order that the pigments dissolve.
The Art Form
Unlike permanent hair colour, which stops oxidising after the development time is complete, bleach continues to oxidise until it is removed from the hair or dries out. This means that a colourist needs to be both skilled and knowledgeable to ensure their client’s hair is safely lifted to the target shade.
Bleaching hair is an art form
Before commencing any bleaching service a colourist must perform a detailed hair and scalp analysis to identify any contra-indications that may result in an adverse result. Previous hair colour or chemical services, hair texture, hair characteristics, elasticity and porosity all need to be analysed.
It takes experience and critical analysis to determine whether the target shade can be achieved. An experienced colourist will not ignore contra-indications. Bleaching the hair increases porosity and can degrade elasticity. If bleach is over processed it can easily destroy the cuticle and cortex cells that are responsible for supporting the strength of the hair.
How light can bleach lift the hair?
Another reason why bleaching hair is an art form is because an experienced colourist will know which hydrogen peroxide to choose for the service and when to remove the product.
Generally, your manufacturer will state that their bleach will lift 7 to 8 levels of lift, however; this really is the ideal scenario – virgin hair, excellent condition, fine texture, good porosity and good elasticity. Once you add previous colour services, a compacted cuticle, coarse texture, poor porosity or poor elasticity into the mix the amount of lift that can be achieved is reduced.
Knowing when to say no!
There are so many variables that affect the successful outcome of a bleaching service but the most important is knowing when to say no! An experienced colourist will extract an entire hair history of at least five years from their clients. They will confidently say no to clients that have a hair history that would prevent them achieving lighter hair safely.
Bleaching hair tutorials on MHD
If you are looking to turn your bleaching services into both an art form and a science, explore the variety of colouring hair tutorials we have on MHD. In particular:
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