Chemistry Blog

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Jan 31

The Chemistry of Hair Relaxers

by Mark | Categories: general chemistry | (15834 Views)

I run a science communication module for undergraduate students. One of the assessments involves writing a blog or news style article. This year’s students did a cracking job so I’d like to share some of them with you. So enough from me and over to Ola Odu, a 3rd Year biochemistry student at the University of Hull.

Twitter: @olaodu_
Instagram: @olaodu_

 

Untangling the mystery of how relaxers work and delving into the chemistry behind the process to reveal how kinks, curls and coils are smoothed into a sleek style

The use of hair relaxers is something that is very common among women of colour all over the world and despite its name, the process is far from relaxing. The desire for silky, straight hair stems from the way the media present these flowing locks to be the epitome of beauty, but this comes at a price. From a young age, many girls, myself included, are unfamiliar with their natural hair texture as a result of their attempts to conform to this standard to beauty that they are constantly surrounded by. Despite the widespread use of relaxers, many of us would never consider how they work on a scientific level. Now that I have embraced my natural hair, I look back on the relaxers that I depended on for so long to find out what they really did to my hair.

 

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My relaxed hair 5 years ago compared to my natural hair now


My relaxed hair 5 years ago compared to my natural hair now

Relaxers come in a range of brands, strengths and consistencies, but how do they work? Essentially, it’s a straight perm, usually used by people with thick and tightly coiled hair so that it is easier to manage. Instead of using heat to straighten the hair, chemicals are used to loosen the tightly set curls. Hair fibres are made up of proteins, mainly keratin, that contain different types of bonds which are responsible for each individual’s distinctive hair texture. Hydrogen and disulphide bonds are a main factor in determining the curl pattern of the hair. Hydrogen bonds are bonds that form between water molecules, and are responsible for hair curling as it dries. When hair is wet, the hydrogen bonds are broken. As it dries, the bonds reform, as do the curls. This is why hair can be manipulated by using rollers as a temporary alternative to relaxers. As the hair dries around the rollers, it
holds its new shape once they are removed.

How hydrogen bonds in hair are broken and reformed

Disulfide bonds are much stronger than hydrogen bonds. These bonds form between sulfur atoms in hair fibres in order to provide strength in addition to the formation of curls. These bonds cannot be broken by water like hydrogen bonds, so hair relaxers are used. The chemicals present in hair relaxers break the disulfide bonds. This permanently straightens the hair. However, breaking these bonds makes the hair more susceptible to breakage and split ends.

Illustration of disulphide bonds in hair fibres breaking due to the use of hair relaxer

The relaxers are strong enough to break the disulfide bonds in hair fibres and consequently alter the structure of the curl pattern. This because of their typically high pH. In chemistry, pH is a numeric scale used to state how acidic or basic a substance is. If it has a low pH, it is more acidic and if the pH is high, it is more basic. Hair relaxers are basic, with their pH ranging from 9 to 14 to ensure that they are strong enough to change the hair structure.

 

There are different types of hair relaxers available of varying strengths and made up of different chemicals. Thio (short for ammonium thioglycolate) relaxers are much thicker in consistency than other relaxers, which makes them easier to apply. They have a pH value of at least 10 to ensure that enough of the disulfide bonds have broken. The relaxer is then rinsed out and a neutraliser used to bring the hair back to its original pH value of 4.5 – 5.5. Thio relaxers slowly break down the bonds in the hair’s proteins in order to straighten it.

However, lye relaxers work in a slightly different way. In this process, lye is the active ingredient. Lye is a mixture of sodium hydroxide, water, petroleum jelly, mineral oil and emulsifiers. This relaxer is absorbed by the hair’s proteins and weakens the bonds rather than breaking them. The curls are then loosened as the hair fibre swells open. However, the amount of lye in the relaxer can vary, so weaker products can minimise the extent of damage to the scalp. Lye relaxers typically have a pH between 12 and 14 and do not require a special neutralising step, unlike thiol relaxers.

Increasing awareness of the potentially harmful effects of sodium hydroxide led to the development of no-lye relaxers. They work in the same way as lye relaxers, but the sodium hydroxide was replaced with potassium, lithium or guanidine hydroxides. This means no-lye relaxers are gentler on the scalp.

Once the hair is relaxed, it is permanently straightened. But as the hair continues to grow, the roots will be natural. This means the relaxing process should be repeated regularly to achieve a consistent look, but excessive use of relaxers can cause damage over time, leading to chemical burns and hair loss. Relaxers contain strong chemicals to ensure that all the bonds holding the curls are altered. These chemicals can be harmful if overused or applied incorrectly.

Overall, hair relaxers are useful in managing thick, tightly coiled hair when used moderately. But, it is a permanent alteration to the hair’s curl pattern, so it is something that should be well considered before undertaking. Personally, my hair is much healthier without the use of relaxers, but this is not the case for everyone. What you do with your hair is your choice and should come from you, and you alone. Ultimately, all hair textures are wonderful and beautiful in their own way and should be celebrated!

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