6.2 Chemical Hair Relaxers & Curl Reforming Systems

Chemical Hair Relaxers & Curl Reforming Systems

Chemical hair relaxing is the process of permanently rearranging the internal structure of curly or coiled hair into a straight, smooth form. While permanent waving introduces curl into straight hair through reduction and oxidation, chemical relaxers remove curl through intense chemical restructuring. Hair relaxers fall into two major chemical categories: hydroxide relaxers and ammonium thioglycolate (thio) relaxers. These two chemical families operate through fundamentally incompatible chemical pathways and can never be used together on the same head of hair.

---

Hydroxide Relaxers & The Chemistry of Lanthionization

Hydroxide relaxers are extraordinarily strong alkalis with pH values ranging from 12.5 up to 14.0. Active hydroxide ions ($OH^−$) swell the cuticle aggressively and penetrate deep into the cortex to alter the hair's structural integrity.

The Mechanism of Lanthionization

Unlike permanent waves or thio relaxers, hydroxide relaxers do not break disulfide bonds through reduction, nor can the broken bonds be rebuilt with an oxidizing neutralizer. Instead, hydroxide relaxers permanently alter disulfide bonds through a chemical reaction called lanthionization.

In lanthionization, the highly reactive hydroxide ion removes one sulfur atom from a disulfide bond (-S-S-), converting it into a lanthionine bond (-S-):

$\text{Keratin-S-S-Keratin} + \text{OH}^- \longrightarrow \text{Keratin-S-Keratin} + \text{H}_2\text{O} + \text{S}^{2-}$

A natural disulfide bond contains two sulfur atoms connecting two cysteine amino acids. A lanthionine bond contains only a single sulfur atom. Because a sulfur atom has been permanently cleaved from the molecular chain, lanthionine bonds can never be reformed. Oxidizing agents (such as hydrogen peroxide neutralizers) have zero effect on lanthionine bonds. Consequently, hair straightened with a hydroxide relaxer is permanently relaxed and can never be re-bonded.

---

Formulations: Hydroxide vs. Thio Relaxers

1. Sodium Hydroxide Relaxers (Lye Relaxers)

Sodium hydroxide relaxers are the traditional standard for professional chemical relaxing. Containing sodium hydroxide ($NaOH$, commonly called lye or caustic soda), they require no mixing and work very rapidly. However, sodium hydroxide is highly caustic and capable of inflicting severe chemical burns on the scalp and permanent corneal damage if splashed into the eyes. A protective base cream must be applied to shield the scalp, ears, and hairline.

2. Potassium & Lithium Hydroxide Relaxers

Marketed commercially as "no-mix, no-lye" relaxers, potassium and lithium hydroxide formulations operate at a high pH (12.5–13.5). While they avoid sodium hydroxide, they are strong alkaline metal hydroxides that straighten hair via lanthionization and carry the same caustic risks to the scalp as traditional lye.

3. Guanidine Hydroxide Relaxers

Guanidine hydroxide relaxers are sold as "no-lye" systems and are popular for clients with sensitive scalps. The product is packaged as a two-component system: a calcium hydroxide relaxer cream and a liquid activator containing guanidine carbonate. The cosmetologist must mix these two components immediately prior to application, generating guanidine hydroxide chemically in the bowl.

While guanidine hydroxide causes less stinging and burning on the scalp, it is chemically drying to the hair shaft. Furthermore, calcium ions precipitate onto the hair fiber as an insoluble mineral film, leaving the hair brittle, dry, and dull unless treated with clarifying and chelating shampoos.

4. Ammonium Thioglycolate (Thio) Relaxers

Thio relaxers use the same active reducing agent as permanent waves (ammonium thioglycolate), formulated at a higher concentration and thicker cream viscosity with a pH of 9.0 to 11.5. Thio relaxers break disulfide bonds by reduction (adding hydrogen) rather than lanthionization. After processing and rinsing, an oxidizing neutralizer (hydrogen peroxide) rebuilds the bonds into a straight form. Thio relaxers are gentler on the scalp than hydroxide relaxers, but they are less effective on very coarse or tightly coiled curl patterns.

---

Base vs. No-Base Relaxers

Protecting the client's scalp from high-alkalinity chemical irritation is a mandatory safety requirement:

• Base Relaxers: Formulated without built-in protective oils. They require the cosmetologist to apply a thick layer of petroleum-based protective cream across the entire scalp, perimeter hairline, and ears before applying any relaxer.
• No-Base Relaxers: Formulated with protective oils and conditioning agents that melt at body temperature (approx. 98.6°F / 37°C) when applied to the hair, automatically depositing a protective film over the scalp. However, even when using no-base relaxers, a protective base cream must be applied around the client's perimeter hairline, neck, and ears.

---

Application Protocols: Virgin vs. Retouch Relaxers

Chemical relaxer application requires precision, careful speed, and strict avoidance of product overlapping.

Virgin Relaxer Application

A virgin relaxer is performed on hair that has never received chemical relaxing:

1. Divide dry, unwashed hair into four clean quadrants.
2. Apply protective base cream to the entire hairline, ears, and nape.
3. Begin application in the most resistant quadrant (usually the lower nape).
4. Apply the relaxer 1/4 to 1/2 inch away from the scalp, extending down the hair strand and stopping short of the porous ends.
5. Rationale: Scalp body heat accelerates chemical processing at the roots, while hair ends are older, more porous, and absorb chemicals quickly. Applying to the midshaft first guarantees uniform processing.
6. After the midshaft has relaxed sufficiently, apply relaxer to the scalp area and porous ends last.
7. Smooth the product using the back of a hard-rubber comb or gloved fingers until the desired degree of straightness is achieved.

Retouch Relaxer Application

A retouch relaxer is performed on hair that has previously been relaxed, targeting new growth (typically every 6 to 8 weeks):

1. Divide hair into four quadrants and apply protective base cream to the entire scalp, hairline, ears, and previously relaxed hair.
2. Apply the relaxer strictly to the new growth only, starting 1/4 inch from the scalp up to the line of demarcation.
3. Do not apply relaxer over previously relaxed hair.

---

Curl Re-Forming (Soft Curl Permanents)

Curl re-forming (commonly known as a soft curl permanent) restructures tightly coiled or curly hair into larger, looser, more manageable curls. It is a multi-step service based exclusively on ammonium thioglycolate chemistry (it cannot be performed on hydroxide-relaxed hair):

1. Thio Relaxer (Rearranger): An ammonium thioglycolate cream is applied to soften and relax the natural curl pattern into a straight state. Once relaxed, the hair is rinsed thoroughly with warm water.
2. Rod Wrapping: The softened, pliable hair is wrapped onto permanent wave rods using chosen base controls and sectioning patterns to determine the new curl diameter.
3. Thio Booster (Waving Lotion): A liquid thioglycolate lotion is applied to saturate the wrapped rods, softening the hair around the rod contours.
4. Neutralization: An oxidizing neutralizer (hydrogen peroxide) is applied to rebuild disulfide bonds, permanently locking in the enlarged curl pattern.