11.3 Relaxers, Curl Reduction & Keratin Smoothing

Chemical hair relaxing rearranges curly or tightly coiled hair into a straighter or looser form. The NIC theory outline names hydroxide, thio, and keratin under relaxer/restructurizer and curl reduction. Those three words are not three strengths of the same cream. They are three chemistries. Pick the wrong family for the client’s history and you get breakage, not a smoother pattern.

Sodium hydroxide (lye)

Sodium hydroxide (NaOH) relaxers are the traditional lye relaxers. They sit at the top of the alkalinity ladder (typically about pH 12–14) and lanthionize disulfide bonds. They can process resistant, tightly coiled hair efficiently. They also demand scalp integrity, timing, and no overlap. Many lye relaxers are base relaxers: you apply a protective base cream to the entire scalp, along the hairline, and on the ears before the cream relaxer goes on the hair. Base cream is a physical barrier, not a permission slip to ignore abrasions. If the scalp is inflamed, open, or infected, you do not relax it—see Section 11.4 and OAC 175:10-7-20.

Lithium and potassium hydroxide (metal “no-lye”)

Lithium hydroxide and potassium hydroxide relaxers are still hydroxide relaxers. Marketing often says no-lye because they are not sodium hydroxide. The active chemistry is still a hydroxide ion at extreme pH doing lanthionization. They can feel different on the scalp and may be chosen for clients who do not tolerate sodium hydroxide well, but they are not thio, not near the acid mantle, and not compatible with a later conventional perm. “No-lye” on a theory item is a vocabulary trap if you translate it as “gentle like conditioner.”

Guanidine hydroxide (mix-type “no-lye”)

Guanidine hydroxide relaxers are typically sold as two parts: a calcium hydroxide cream mixed with a guanidine carbonate activator to form guanidine hydroxide at use. They are also marketed as no-lye. They still lanthionize. They often process with less immediate scalp sting than sodium hydroxide for some clients, which can hide overprocessing because the client is not yelling while the midshaft is cooking. Timing and comb tests still rule. Mix only as the label directs—OAC 175:10-7-3(e) and (g)—and do not invent a third bottle “to speed it up.”

All hydroxide families share the overlap ban: never apply hydroxide on previously hydroxide-relaxed hair, only on new growth at retouch.

Ammonium thioglycolate relaxers and thio curl reducers

Thio relaxers and curl reducers use ammonium thioglycolate (or a close thio relative) at a strongly alkaline but lower pH than hydroxide (often taught near pH 9–10). They reduce disulfide bonds. After smoothing, you rinse and use the labeled oxidizer/neutralizer to rebuild disulfide bonds in the straighter or looser shape—the same oxidation idea as a perm, without rods (or with rods later in a soft-curl reformation).

Thio curl reduction is how some clients keep more pattern than a hydroxide would leave. Curl reformation / soft-curl services (thio relax, then thio wrap) exist only on hair that is thio-compatible. Hair with a hydroxide history is not that hair.

Do not “touch up” a hydroxide relaxer with thio cream, or a thio relaxer with hydroxide cream, because the last jar was closer to the chair. Incompatible overlay is one of the highest-yield safety items in this chapter.

Base cream, virgin versus retouch, smoothing

Protective base cream goes on skin that should not receive hydroxide: scalp (for base formulas), ears, hairline, nape. No-base relaxers include oils or a built-in protective component in the cream; you still protect ears and hairline as the manufacturer directs and you still do not treat an open scalp. “No-base” does not mean “no drape, no gloves, no timing.”

Virgin relaxer (no previous relaxer on the lengths): apply to the most resistant hair first, usually midshaft, then toward the ends if they need it, and last to the scalp area, because scalp body heat speeds processing. Keep cream off the scalp by a small margin even on virgin work unless the label’s virgin method says otherwise. Smooth with the back of a comb or fingers per training—gentle tension, no scraping. Watch the pattern loosen. Strand / smoothing checks beat a wall clock used alone, but you still do not exceed labeled maximum time.

Retouch: apply only to new growth. Leave a tiny buffer so cream does not sit on the previously relaxed line. Overlap is how hair breaks in a ring. If ends are dry, they need conditioner or a trim, not a second hydroxide coat.

Rinse thoroughly with warm water until the hair is clean of cream, keeping water running away from the eyes. Then use the neutralizing shampoo the relaxer system specifies. For hydroxide, that shampoo is an acid–alkali neutralization: it drops pH and deactivates leftover hydroxide. It is not the same chemical event as a perm’s peroxide rebuilding disulfide bonds. If you skip it, alkali stays in the fiber, the cuticle stays blown open, and breakage continues in the towel.

Oklahoma practical relaxer-type supplies

The same OSBCB cosmetology exam page lists a cholesterol / spatula / chemical brush and bowl cluster (no applicator bottle for that cluster), plus disposable gloves, clips, and a non-metal tail or all-purpose comb. Cholesterol cream is the usual mock product for demonstrating relaxer application on a mannequin—thick enough to show virgin or retouch placement without using live sodium hydroxide in the exam room. Know the difference: theory still asks lye versus no-lye versus thio; practical scoring still wants safe placement, gloves, and the Board’s tools.

Keratin and smoothing systems

Keratin smoothing and related chemical restructurizers appear on the NIC outline beside hydroxide and thio. Many professional smoothing systems, especially older “Brazilian” heat-flat-iron protocols, can release formaldehyde or formaldehyde-releasing species (including methylene glycol language on some SDS documents) when heated. That is an inhalation and OSHA Hazard Communication problem as much as a hair problem. Teach it this way:

• Read the SDS (Section 2 hazards, Section 8 ventilation and PPE, Section 10 reactivity) and the use label before you ever turn the iron on.
• OAC 175:10-7-3(a) requires rooms to have ventilation adequate to clear product fumes, with the rule’s examples including artificial nail products and bleach; a formaldehyde-releasing iron service is exactly the kind of fume load that sentence is for.
• OAC 175:10-7-3(e) and (g): mix and apply only as labeled, including any required patch test; do not mix with some other straightening cream unless the label expressly says to.
• OpenExamPrep has not found an Oklahoma Administrative Code section that bans keratin smoothing by name. Do not invent a Board keratin prohibition on the exam. Control the service with label, SDS, ventilation, and contraindications (compromised hair, incompatible prior chemicals, pregnancy/respiratory concerns as the manufacturer and medical referral require).
• Do not market a keratin service as “formaldehyde-free” unless the SDS actually supports that claim. Do not treat keratin as a hydroxide retouch or as a perm. It is its own labeled protocol, often with heat, gloves, and no scalp flooding.

If the client’s record shows recent hydroxide, recent bleach, or metallic dye, a smoothing iron plus aldehyde chemistry is not a “gentle alternative” you invent on the fly. Strand-test or refuse.