Sodium Hydroxide in Hair Relaxers: Breaking the Bonds of Curls

by Team Wild

What is Sodium Hydroxide?
Lye or Caustic Soda
Often referred to as lye or caustic soda, sodium hydroxide is a synthetic compound. It's commonly used in the manufacturing of soaps, detergents, and as a key ingredient in chemical hair relaxers.
Highly Alkaline
Sodium hydroxide is a highly alkaline substance, registering a pH of 14, indicating its strong base properties. This extreme alkalinity is what allows it to break down the disulfide bonds in hair, facilitating the straightening process.
The Structure of Hair
Round Follicles
Round hair follicles produce straight hair because the hair grows out evenly in all directions. This even growth pattern results in a smooth, straight hair shaft without any natural bends or curves.
Oval/Curved Follicles
Oval or curved hair follicles cause hair to grow out asymmetrically, resulting in curls or waves. The uneven growth creates bends and twists in the hair shaft as it emerges from the follicle.
Disulfide Bonds
Disulfide bonds are chemical links between cysteine amino acids in the hair protein (keratin). These bonds determine and maintain the hair's natural shape, providing strength and resistance to external forces.
Disulfide Bonds: The Hair's Building Blocks
Strong Bonds
Disulfide bonds are strong chemical bonds within hair protein (keratin).
Located in the Cortex
They are found in the hair's cortex, the middle layer of the hair shaft.
More Bonds = Curlier Hair
The more disulfide bonds present, the curlier the hair.
Altered by Chemical Treatments
Disulfide bonds can only be altered by chemical treatments like perms or relaxers.
How Sodium Hydroxide Works in Hair Relaxers
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Sodium hydroxide breaks down the disulfide bonds in hair.
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This weakens the hair's structure temporarily, allowing it to be reshaped.
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The hair is then straightened and the new shape is "locked in" as the bonds reform.
The Chemical Process
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Sodium hydroxide (NaOH) is applied to hair.
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In water, NaOH separates into Na+ and OH- ions.
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The OH- ions break the disulfide bonds in the hair.
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This makes the hair more pliable and easy to straighten.
Effects of Sodium Hydroxide on Hair
Sodium hydroxide straightens hair permanently.
Improper use can damage hair, leading to breakage, dryness, and scalp irritation.
Professional application is crucial for safe and effective results.
Safety and Alternatives
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Sodium hydroxide is highly alkaline (pH 14) and should be handled with caution.
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"No-lye" relaxers utilize different alkaline compounds.
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Professional application is always recommended for safe and effective results.
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Natural alternatives, like steam rolling, can provide temporary straightening.
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Using organic hair products is the safest alternative.