Chemical Texture Services (Perms and Relaxers)
Chapter Introduction
Chemical texture services modify the internal structure of the hair by breaking and reforming disulfide bonds. These services represent a significant portion of the Red Seal exam for hairstylists. This chapter covers the scientific principles, technical procedures, dilution calculations, safety standards, and common pitfalls. You must master the distinction between permanent wave services (which add curl) and relaxing services (which reduce curl), as well as the chemicals involved in each.
Fundamental Principles of Hair Chemistry
Hair Structure
Hair is composed of approximately 90% keratin, a fibrous protein. The hair shaft consists of three layers:
The cuticle: the protective outer layer, made up of overlapping scales.
The cortex: the middle layer containing disulfide bonds (S–S bridges), hydrogen bonds, and salt bonds. This is where chemical changes occur.
The medulla: the central layer, often absent in fine hair.
Disulfide bonds are the strongest and are formed between two cysteine amino acids. They are responsible for the natural shape of the hair. Hydrogen and salt bonds are weaker and break temporarily with water or heat.
pH and Its Role
pH measures the acidity or alkalinity of a solution on a scale of 0 to 14. The pH of hair and scalp ranges between 4.5 and 5.5. Chemical texture products alter this pH to open the cuticle and allow active agents to penetrate.
| Product Type | Typical pH | Effect on Hair |
|---|
| Gentle shampoo | 5.0 – 6.5 | Keeps the cuticle closed |
| Alkaline perm solution | 8.0 – 9.5 | Opens the cuticle, swells the cortex |
| Acid perm solution | 6.5 – 7.5 | Moderately opens the cuticle |
| Relaxer (thioglycolate) | 9.0 – 14.0 | Strongly opens the cuticle |
| Neutralizer (peroxide) | 3.0 – 5.0 | Closes the cuticle, reforms bonds |
Reducing and Oxidizing Agents
Perms and relaxers rely on two chemical steps:
17.Reduction: the reducing agent (usually ammonium thioglycolate or sodium hydroxide) breaks disulfide bonds by converting them into thiol bonds (–SH). This step softens the hair and makes it malleable.
18.Oxidation: the oxidizing agent (usually hydrogen peroxide or a sodium bromate solution) reforms the disulfide bonds in their new position. This step is called neutralization.
The simplified chemical formula for reduction is:
S–S + 2H → 2SH
The reverse reaction during neutralization is:
2SH + O → S–S + H₂O
Permanent Waving
Definition and Purpose
A permanent wave is a chemical service that changes the shape of the hair by adding waves or curls. It can be performed on natural or colored hair, but special precautions apply in the latter case.
Types of Perms
Alkaline Perm (Thioglycolate)
The alkaline perm uses ammonium thioglycolate as the reducing agent, with a pH of 8.0 to 9.5. It produces firm, long-lasting curls. It is suitable for healthy, resistant hair. The processing time is generally 10 to 20 minutes.
Acid Perm (Glyceryl Thioglycolate)
The acid perm uses glyceryl thioglycolate with a pH of 6.5 to 7.5. It produces softer curls and is gentler on fragile or colored hair. The processing time is longer (15 to 30 minutes) and often requires external heat (hood dryer or steam) to activate the reaction.
Exothermic Perm
The exothermic perm produces a chemical reaction that generates heat. It uses a special formulation that activates upon contact with air or an activator. It is fast but carries a risk of overprocessing if not monitored carefully.
Perm Procedure
The complete procedure includes the following steps:
36.Hair and scalp analysis: check elasticity, porosity, density, and scalp condition. Perform a sensitivity test (patch test) 24 to 48 hours before the service.
37.Client preparation: seat the client comfortably, protect clothing with a waterproof cape, and apply a protective cream around the hairline.
38.Shampoo: use a clarifying (residue-free) shampoo to remove product buildup. Do not massage the scalp vigorously to avoid irritating the skin.
39.Winding: divide the hair into sections (usually 4 to 6 sections) and wind strands onto rods of the appropriate diameter. Tension should be even and moderate.
40.Solution application: apply the perm solution evenly to each rod. The processing time begins once application is complete.
41.Processing test: unwind one rod from the most resistant area after the minimum recommended time. Check curl formation by forming an "S" shape with the hair.
42.Rinsing: rinse thoroughly with warm water (5 to 10 minutes) to remove all solution.
43.Blotting: gently blot the rods with a towel to remove excess water.
44.Neutralization: apply the neutralizer to each rod. Leave on according to the manufacturer's instructions (usually 5 to 10 minutes).
45.Final rinse and rod removal: rinse with warm water, remove the rods, and apply an acidifying conditioner to close the cuticle.
Dilution and Time Calculations
Processing time depends on several factors:
The strength of the solution (thioglycolate concentration)
The pH of the solution
Hair porosity and elasticity
Ambient temperature
The general rule is that processing time should be reduced by 50% for fine or highly porous hair, and increased by 50% for thick or resistant hair.
Calculation example: if the standard time is 15 minutes for an alkaline perm on normal hair, for fine, porous hair the time will be 15 × 0.5 = 7.5 minutes. For thick, resistant hair, the time will be 15 × 1.5 = 22.5 minutes.
Rod Diameter and Curl Type
Rod diameter determines curl size:
| Rod Diameter | Curl Size | Visual Effect |
|---|
| 1.0 – 1.5 cm | Very tight curl | Afro effect, springy |
| 1.5 – 2.5 cm | Medium curl | Defined wave |
| 2.5 – 4.0 cm | Large curl | Soft wave, volume |
| 4.0 cm and up | Loose wave | Subtle movement |
Relaxing
Definition and Purpose
Relaxing is a chemical service that reduces or eliminates the natural curl of the hair. It is also called chemical relaxing or straightening. It uses powerful alkaline agents to break disulfide bonds and reform the hair in a straight position.
Types of Relaxers
Thioglycolate-Based Relaxers
Ammonium thioglycolate is used at higher concentrations than for perms (pH 9.0 to 10.0). It is gentler than sodium hydroxide and suitable for colored or fragile hair. The processing time is 10 to 20 minutes.
Sodium Hydroxide-Based Relaxers (Caustic Soda)
Sodium hydroxide (NaOH) is a strong alkali with a pH of 13.0 to 14.0. It breaks disulfide bonds irreversibly. It produces fast relaxing (5 to 10 minutes) but carries a high risk of chemical burns and hair breakage. It must never be used on colored or bleached hair.
Guanidine Hydroxide-Based Relaxers
Guanidine hydroxide is a no-lye alternative, with a pH of 13.0 to 13.5. It is less irritating than sodium hydroxide but equally effective. It is often used for sensitive scalps.
Relaxing Procedure
69.Preliminary analysis: assess hair texture, porosity, and condition. Perform a strand test to determine the exact processing time.
70.Protection: apply a protective barrier (petroleum jelly or cream) to the scalp and ears.
71.Application: divide the hair into sections (usually 4 sections). Apply the relaxer with a brush, starting with the least sensitive area (the nape) and finishing at the crown (the warmest area).
72.Smoothing: use a wide-tooth comb or the back of the brush to smooth the hair continuously until the natural curl is eliminated.
73.Smoothing test: check regularly by lifting a strand and observing the formation of an "S" wave.
74.Rinsing: rinse thoroughly with warm water for 5 to 10 minutes to remove all product.
75.Neutralization: apply an acidifying neutralizer (acidifying shampoo or neutralizing solution) to reform the bonds and close the cuticle.
76.Conditioning: apply a deep conditioner to restore moisture.
Processing Time Calculation
Relaxer processing time depends on hair type:
| Hair Type | Processing Time (Sodium Hydroxide) | Processing Time (Thioglycolate) |
|---|
| Fine and porous | 3 – 5 minutes | 5 – 8 minutes |
| Normal | 5 – 8 minutes | 8 – 12 minutes |
| Thick and resistant | 8 – 10 minutes | 12 – 15 minutes |
Important rule: processing time begins once application is complete on the entire head, not at the start of application.
Safety and Standards
Canadian Electrical Code
Hair salons must comply with the Canadian Electrical Code, Part I (CE Code) for all electrical installations. Rule 8-200 covers branch circuits and current capacities. Electrical equipment used (hood dryers, flat irons, sterilizers) must meet CSA standards and be inspected regularly.
CSA B149.1
The CSA B149.1 standard (Natural Gas and Propane Installation Code) applies to water heaters and heating systems used in salons. Installations must be inspected by a certified technician.
Hygiene and Sanitation
Wear disposable gloves when applying chemical products.
Use clean towels for each client.
Disinfect tools (combs, brushes, rods) between each client with a high-level or intermediate-level disinfectant.
Discard expired products or those whose integrity is compromised.
Ventilation
Chemical texture products emit potentially irritating vapors. The salon must have adequate ventilation (air extraction or mechanical ventilation system) to maintain air quality.
Common Pitfalls to Avoid
96.Confusing processing times: perm timing starts at the end of application, not the beginning. For relaxers, timing also starts once application is complete on the entire head.
97.Neglecting the sensitivity test: the patch test is mandatory 24 to 48 hours before the service. A strand test is also necessary to verify product compatibility.
98.Using sodium hydroxide relaxers on colored hair: this causes immediate and irreversible breakage. Use a thioglycolate- or guanidine-based product instead.
99.Oversaturating the rods: excessive perm solution application can drip onto the scalp and cause chemical burns.
100.Skipping complete neutralization: incomplete neutralization leaves thiol bonds unreformed, which weakens the hair and causes the natural curl to return.
101.Confusing product pH: the neutralizer pH is acidic (3.0 – 5.0), not alkaline. An incorrect pH will not close the cuticle.
102.Ignoring contraindications: do not perform perms or relaxers on an irritated, damaged, or infected scalp.
103.Using metal rods with alkaline products: metal can react with chemicals and cause burns. Use plastic or rubber rods.
104.Failing to document the service: record the product type, concentration, processing time, and results for each client. This documentation is essential for future services.
105.Confusing the standards: the Canadian Electrical Code applies to electrical installations, while CSA B149.1 applies to gas installations. Do not mix them up.
Exam Tips
Memorize the pH ranges for each product type (see the table in the pH section).
Learn the basic chemical formulas: ammonium thioglycolate, sodium hydroxide, hydrogen peroxide.
Understand the difference between disulfide, hydrogen, and salt bonds.
Practice calculating processing times based on hair porosity and thickness.
Review the procedure steps in exact order: analysis, test, shampoo, application, processing, rinsing, neutralization, conditioning.
Know the absolute contraindications: irritated scalp, bleached hair with sodium hydroxide, pregnancy (special precautions).
Summary
Perms and relaxers modify hair structure by breaking disulfide bonds through reduction, then reforming them through oxidation.
Product pH determines aggressiveness: the higher the pH, the more alkaline the product and the more it opens the cuticle.
Alkaline perms (pH 8.0 – 9.5) produce firm curls; acid perms (pH 6.5 – 7.5) produce soft curls.
Relaxing uses strong alkalis (sodium hydroxide, guanidine hydroxide) or high-concentration thioglycolate.
Processing time depends on hair type, porosity, and product concentration.
Neutralization is a critical step that reforms disulfide bonds and closes the cuticle.
Safety standards include the Canadian Electrical Code, Part I (CE Code) and CSA B149.1 for gas installations.
Hygiene, ventilation, and pretesting are essential to prevent complications.
Common pitfalls include timing errors, inappropriate product use on colored hair, and neglecting neutralization.
Review Questions
127.What is the typical pH of an alkaline perm solution?
128.What is the function of the reducing agent in a perm?
129.What type of relaxer must never be used on colored hair?
130.What is the recommended processing time for a sodium hydroxide relaxer on normal hair?
131.Which Canadian standard applies to electrical installations in a hair salon?
132.Why is neutralization essential after a perm?
133.What rod diameter is recommended for a tight curl?
134.What is the difference between disulfide bonds and hydrogen bonds?
135.What is the typical pH of a neutralizer?
136.What are the absolute contraindications for a chemical texture service?
This chapter covers the essential knowledge for the Red Seal exam in hairstyling. Review regularly and practice time calculations to master this material.
