6.4 Chemical Straightening, Keratin Smoothing and Texture Service Tests
Key Takeaways
Keratin smoothing treatments coat the hair with keratin and polymers that are sealed with a flat iron; many release formaldehyde when heated, so OSHA's formaldehyde limits and ventilation apply.
Thio straightening (thermal reconditioning) uses a thioglycolate solution, rinsing, flat ironing and a neutralizer, and is incompatible with hair previously treated with hydroxide relaxers.
Perm and relaxer services begin with draping (towel, chemical cape, towel), scalp examination and sectioning, usually into nine panels for perms and four quadrants for relaxers.
A preliminary test curl shows how the hair will process; a relaxer strand test checks straightening time and condition; a patch test is offered whenever the manufacturer recommends one.
Product selection follows the hair: alkaline (thio) waves for coarse resistant hair, acid or acid-balanced waves for porous or color-treated hair, and the mildest relaxer strength that will achieve the goal.
Why this section matters
Chemical texture services are 11% of general theory, and permanent waving and chemical relaxing are 7% each of the written practical. The written practical lists the same seven steps for each: draping, sectioning, application and processing, product selection, strand test and patch test. Section 6.1 covers perm chemistry and wrapping, 6.2 relaxer chemistry and application, and 6.3 consultation and safety; this section fills in straightening services and the setup and test steps.
Keratin smoothing treatments
Keratin smoothing treatments (often called Brazilian blowouts) reduce frizz and curl for several weeks to a few months.
- Clarify the hair to remove buildup.
- Apply the smoothing solution (keratin, silicones and polymers) in thin sections.
- Blow-dry thoroughly.
- Seal small sections with a flat iron, often at a high temperature set by the manufacturer.
- Follow the manufacturer's aftercare (some require waiting before shampooing).
Formaldehyde hazard. Many smoothing products contain formaldehyde or methylene glycol, which releases formaldehyde gas when heated. Formaldehyde irritates the eyes, nose and lungs, is a sensitizer, and is a human carcinogen. OSHA's formaldehyde standard (29 CFR 1910.1048) sets a permissible exposure limit of 0.75 ppm over 8 hours and a 15-minute short-term limit of 2 ppm, and requires hazard information on labels and safety data sheets even for products labeled "formaldehyde-free" that release it. Use the product as directed, with local exhaust ventilation, and give clients and staff the hazard information.
Thio straightening (thermal reconditioning)
Sometimes called Japanese straightening, this permanently straightens hair with thioglycolate chemistry:
- Apply the thio straightening solution and process as directed.
- Rinse thoroughly and blow-dry.
- Flat iron in small sections to set the hair straight.
- Apply the neutralizer (an oxidizer) to rebuild the disulfide bonds in the straight shape.
It suits virgin or lightly processed wavy to curly hair. Never use thio products on hair previously treated with a hydroxide relaxer, because lanthionized hair cannot be rebuilt and will break.
Comparing texture services
| Service | Chemistry | Bonds affected | Lasts | Key caution |
|---|---|---|---|---|
| Permanent wave | Thioglycolate or GMTG, then neutralizer | Disulfide bonds broken and rebuilt | Permanent until grown out | Test curls; rinse and blot before neutralizing |
| Hydroxide relaxer | Sodium, lithium, potassium or guanidine hydroxide | Disulfide converted to lanthionine | Permanent | Base the scalp; never overlap; normalizing shampoo |
| Thio relaxer or straightening | Thioglycolate, then neutralizer | Disulfide broken and rebuilt straight | Permanent | Not over hydroxide-treated hair |
| Soft curl permanent | Thio relaxer, rewrap, thio booster, neutralizer | Disulfide broken and rebuilt in a larger curl | Permanent | Thio-only system |
| Keratin smoothing | Keratin and polymers sealed with heat | Mostly temporary coating and hydrogen bonds | Weeks to months | Formaldehyde exposure; ventilation |
Setting up perm and relaxer services
Draping
Use chemical draping: a towel around the neck, a waterproof chemical cape over it, and a second towel over the cape secured at the front. Replace any towel that becomes damp with chemicals (Section 10.1).
Scalp examination and consultation
Check for abrasions, irritation or a contagious condition; a damaged scalp means no chemical service. Ask about prior relaxers, metallic or compound dyes, color, keratin treatments and medications, and record the answers.
Sectioning
- Perms: commonly divide the head into nine panels for a basic wrap (Section 6.1), with subsection size matched to the rod diameter. Other patterns include curvature, bricklay, spiral and piggyback wraps.
- Relaxers: divide the hair into four quadrants (center front to nape, ear to ear) and apply in 1/4- to 1/2-inch subsections, starting in the most resistant area, usually the back.
Product selection
| Client hair | Perm choice | Relaxer choice |
|---|---|---|
| Coarse, resistant, low porosity | Alkaline (thio) wave | Regular or super strength, as the manufacturer directs |
| Normal | Alkaline or acid-balanced wave | Regular strength |
| Fine, porous, color-treated or lightened | Acid or acid-balanced wave | Mild strength, or no relaxer if elasticity is poor |
| Previously hydroxide-relaxed | No thio perm or thio relaxer | Hydroxide retouch on new growth only |
Tests before and during service
| Test | When | What it shows |
|---|---|---|
| Patch test | Offered whenever the manufacturer recommends one (Minn. R. 2105.0375, subp. 7, item F) | Sensitivity or allergy to an ingredient |
| Preliminary test curl (perm) | Before a full perm on hair whose response is uncertain | How the hair processes, the curl that will form, and whether the hair can take a perm |
| Processing test curl (perm) | During processing | Unwind 1 1/2 turns and look for a firm S pattern matching the rod |
| Relaxer strand test | Before the service on a hidden strand, or during processing | Processing time and the degree of straightening; whether the hair breaks |
| Elasticity and porosity tests | During analysis | Whether the hair can tolerate chemicals |
| 1:20 metallic salts test | When metallic or compound dyes are suspected | Whether peroxide or thio will react with metal deposits (Section 6.3) |
Performing a relaxer strand test
Apply relaxer to a small subsection in a less visible area, process while smoothing gently, and check the degree of straightening and the hair's condition at timed intervals. Rinse, and note the time needed. If the hair weakens or breaks, do not proceed.
After the service
Rinse thoroughly. For perms, blot every rod before neutralizing. For hydroxide relaxers, use a normalizing (neutralizing) shampoo; a color-indicator shampoo shows when alkaline residue is gone. Condition, record the products, strength, timing and results, and give home-care advice, including waiting before shampooing if the manufacturer says so.
Why do many keratin smoothing treatments require good local ventilation?
They release ammonia that bleaches the hair
They require a hood dryer for 60 minutes
They contain hydroxide that boils and spatters when it is heated
They can release formaldehyde gas when heated with a flat iron
A client whose hair was previously straightened with a sodium hydroxide relaxer asks for thio straightening on the same hair. What is the correct response?
Proceed after a deep conditioning treatment
Decline; thio products must not be used on hydroxide-relaxed hair because it can break
Proceed using a stronger neutralizer
Proceed, because thio straightening is gentler than hydroxide and will even out the old relaxer
How is the head usually sectioned for a hydroxide relaxer application?
Nine panels, like a basic permanent wave wrap pattern
One section from the crown
Four quadrants, from center front to nape and ear to ear
Diagonal-back sections only, starting at the front hairline
What does a preliminary test curl show before a full permanent wave?
How long the perm will last in months
The client's natural hair level
Whether the client is allergic to the waving lotion or neutralizer ingredients used in the kit
How the hair will process and what curl will form, and whether the hair can take a perm
Sections you finish are checked off in the contents.