Overview
Chemical services are among the most technically demanding procedures in barbering, involving permanent alterations to the hair's internal structure through chemical reactions. This guide covers relaxers, permanent waves, hair color, safety protocols, and the underlying chemistry that connects them all. Mastering these concepts is essential for both the licensing exam and safe professional practice.
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Table of Contents
1. [Chemical Concepts & Hair Structure](#chemical-concepts)
2. [Relaxers](#relaxers)
3. [Permanent Waves](#permanent-waves)
4. [Hair Color](#hair-color)
5. [Safety & Client Protection](#safety)
6. [Quick Review Checklist](#checklist)
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1. Chemical Concepts & Hair Structure {#chemical-concepts}
The Foundation of All Chemical Services
Understanding basic chemistry is the key to understanding why every chemical service works the way it does.
pH Scale
• pH stands for "potential of hydrogen"
• Measured on a scale of 0–14
- 0–6: Acidic
- 7: Neutral
- 8–14: Alkaline (basic)
• Most chemical services (relaxers, perms) are alkaline because high pH opens the cuticle and allows chemicals to penetrate the cortex
• Neutralizing/pH-balancing shampoos lower pH to stop chemical reactions after services
Key Bonds in Hair
| Bond Type | Location | Breakable By | Importance |
|-----------|----------|-------------|------------|
| Disulfide bonds (cystine bonds) | Cortex | Chemical services only | Hold hair's permanent shape |
| Hydrogen bonds | Cortex | Water/heat | Temporary styling |
| Salt bonds | Cortex | pH changes | Temporary changes |
> The most important bond to know: Disulfide bonds are permanently broken during both relaxers and permanent waves, then re-formed (neutralized) in a new position.
Porosity & Processing
• Resistant hair (low porosity): Tightly closed cuticle; repels chemicals; requires longer processing times or additional heat
• High porosity hair: Over-processed or damaged hair that absorbs chemicals too quickly; requires careful monitoring
• Normal porosity: Processes within standard time frames
Key Terms – Chemical Concepts
• Disulfide bonds – Strong side bonds in the cortex that determine hair shape
• pH – Measure of acidity or alkalinity (0–14 scale)
• Alkaline – pH above 7; opens the cuticle
• Resistant hair – Low porosity; tightly closed cuticle
• Cystine bonds – Another name for disulfide bonds
Watch Out For ⚠️
• The pH scale is logarithmic — each unit represents a 10x change in strength
• Do not confuse hydrogen bonds (broken by water) with disulfide bonds (broken only by chemicals)
• "Low porosity" = resistant to chemicals, NOT damaged — do not confuse with over-processed hair
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2. Relaxers {#relaxers}
Overview
Relaxers permanently straighten hair by breaking disulfide bonds, allowing the hair shaft to swell and shift into a straightened position. The bonds are then re-formed straight during neutralization.
Types of Relaxers
#### Sodium Hydroxide (Lye) Relaxers
• Active ingredient: Sodium hydroxide (NaOH)
• How it works: Highly alkaline; swells the hair shaft and permanently breaks disulfide bonds
• Requires base cream: Applied to scalp before service to protect against chemical burns
• Strong caution: NEVER use on hair previously treated with thio (thioglycolate) relaxers
- Mixing sodium hydroxide + thio = severe chemical reaction → hair breakage at scalp
#### No-Lye Relaxers (Guanidine)
• Formed by mixing: Guanidine carbonate + calcium hydroxide
• Result: Creates guanidine hydroxide
• Straightens hair without sodium hydroxide
• Generally milder; less risk of scalp irritation but can cause mineral buildup on hair
The Relaxer Process
1. Apply base cream to scalp (lye relaxers)
2. Apply relaxer to hair
3. Allow processing time — determined by:
- Hair texture
- Hair porosity
- Desired degree of straightness
4. Neutralize with a neutralizing or pH-balancing shampoo
- Lowers pH → closes the cuticle → stops chemical action
Key Terms – Relaxers
• Sodium hydroxide (lye) – Active ingredient in lye relaxers; highly alkaline
• Guanidine hydroxide – Active ingredient in no-lye relaxers
• Base cream – Protective scalp coating applied before lye relaxer services
• Processing time – Duration relaxer remains on hair
• Neutralizing shampoo – Stops relaxer action by lowering pH
Watch Out For ⚠️
• Never mix sodium hydroxide relaxers with thio relaxers — this is a critical safety rule frequently tested
• Base cream is used with lye relaxers, not no-lye relaxers
• Neutralization is done with shampoo for relaxers (NOT the same neutralizer used in perms)
• Over-processing with a relaxer can cause irreversible hair breakage
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3. Permanent Waves {#permanent-waves}
Overview
Permanent waves chemically reshape the hair into a curled or wavy pattern. The process involves two steps: breaking disulfide bonds with a waving solution, then re-forming them in a new position with a neutralizer.
The Two-Step Chemical Process
#### Step 1 – Waving Solution (Reducing Agent)
• Breaks disulfide bonds
• Allows hair to conform to the shape of the rod
#### Step 2 – Neutralizer (Oxidizing Agent)
• Re-forms disulfide bonds in the new curled position
• Makes the wave permanent
• Common neutralizers: hydrogen peroxide or sodium bromate
Types of Permanent Waves
| Feature | Alkaline Wave (Cold Wave) | Acid Wave |
|---------|--------------------------|-----------|
| Primary chemical | Ammonium thioglycolate (ATG) | Glyceryl monothioglycolate |
| pH range | 8.2–9.6 | 4.5–7.0 |
| Heat required? | No — room temperature | Yes — requires heat to process |
| Processing | Faster | Gentler/slower |
| Best for | Normal/resistant hair | Fragile, color-treated hair |
Rod Size & Curl Result
• Smaller rods → tighter, smaller curls
• Larger rods → looser, wider waves
Wrapping Techniques
• Croquignole wrap: Hair wound from ends to scalp in one direction
- Results in tighter curl at ends, looser at scalp
• Spiral wrap: Hair wound at an angle along the rod
- Results in a more uniform curl from scalp to ends
Processing Problems
| Problem | Cause | Result |
|---------|-------|--------|
| Over-processing | Left on too long | Overly porous, weak, frizzy hair; breakage |
| Under-processing | Removed too soon | Weak, limp curl that drops quickly |
Key Terms – Permanent Waves
• Ammonium thioglycolate (ATG) – Primary chemical in alkaline/cold waves
• Neutralizer – Re-forms disulfide bonds; hydrogen peroxide or sodium bromate
• Croquignole – Ends-to-scalp wrapping technique
• Cold wave – Alkaline permanent wave; processes at room temperature
• Over-processing – Results in weak, porous, frizzy hair
Watch Out For ⚠️
• The neutralizer in perms re-forms bonds — do NOT confuse with the neutralizing shampoo used in relaxers
• Acid waves require heat; alkaline waves do not — this is a common trick question
• The smaller the rod, the tighter the curl — this seems obvious but is tested
• Over-processing a perm is permanent damage — it cannot be reversed
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4. Hair Color {#hair-color}
Overview
Hair color services range from temporary to permanent, each working at a different depth within the hair structure. Understanding color levels, developer volumes, and the law of color is essential for both the exam and color correction work.
Hair Color Levels (Classification)
| Level | Type | How It Works | Lasts |
|-------|------|-------------|-------|
| Level 1 | Temporary | Coats outside of cuticle | 1–2 shampoos |
| Level 2 | Semi-permanent | Partially penetrates cuticle | 4–6 shampoos |
| Level 3 | Permanent | Opens cuticle; deposits/lifts color in cortex | Permanently |
Permanent Hair Color – Deep Dive
• Requires hydrogen peroxide (oxidizing agent) to develop
• How it works:
1. Developer opens the cuticle
2. Oxidative dye intermediates (e.g., paraphenylenediamine/PPD) enter the cortex
3. PPD oxidizes → forms large, permanent color molecules that cannot be washed out
• 20-volume (6%) hydrogen peroxide: Most commonly used for gray coverage
- Provides enough lift to open cuticle + allow color deposit
Developer Volumes
| Volume | Lift Level | Common Use |
|--------|-----------|------------|
| 10-volume | Minimal | Deposit only; toning |
| 20-volume | 1–2 levels | Gray coverage; standard color |
| 30-volume | 2–3 levels | Significant lightening |
| 40-volume | 3–4 levels | Maximum lift; high-lift color |
The Law of Color
• Based on the color wheel
• Complementary colors (opposite on the wheel) neutralize each other
| Unwanted Tone | Neutralizing Color |
|--------------|-------------------|
| Red/orange | Green |
| Yellow | Violet/purple |
| Blue | Orange |
| Green | Red |
> Example: To neutralize brassy orange tones after lightening, use a blue-based toner.
Lifting (Lightening)
• Lifting = the lightener's ability to remove/dissolve natural melanin from the hair shaft
• Makes hair progressively lighter
• Stages of lift (darkest to lightest): Black → Brown → Red → Orange → Gold → Yellow → Pale Yellow
Patch Test (Predisposition Test)
• Required before applying any aniline derivative (oxidative/permanent) hair color
• Apply a small amount of color to the inner arm or behind the ear
• Wait 24–48 hours for signs of allergic reaction
• If redness, swelling, or irritation occurs → do NOT proceed with service
Key Terms – Hair Color
• Permanent color (Level 3) – Requires developer; permanently alters cortex
• PPD (paraphenylenediamine) – Oxidative dye intermediate in permanent color
• 20-volume developer – Most common for gray coverage
• Law of color – Complementary colors neutralize each other
• Patch test – Allergy test performed 24–48 hours before aniline derivative color
• Lifting – Removal of natural melanin via lightener
• Aniline derivatives – Chemical compounds in permanent color that can cause allergic reactions
Watch Out For ⚠️
• A patch test is ALWAYS required before permanent (aniline derivative) color — skipping it is both dangerous and a license exam red flag
• 20-volume is the standard for gray coverage — not 10, not 30
• The law of color uses complementary colors to neutralize, not match
• Permanent color works in the cortex; temporary color only coats the cuticle
• Lifting refers to lightening, NOT deposit — know the difference
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5. Safety & Client Protection {#safety}
Personal Protective Equipment (PPE)
The barber must wear during all chemical services:
• ✅ Chemical-resistant gloves (mandatory)
• ✅ Protective apron
• ✅ Eye protection
Pre-Service Testing
| Test | Purpose | Timing |
|------|---------|--------|
| Strand test | Checks how hair responds to chemical; checks color/curl development and hair condition | Before full application |
| Patch test | Detects allergic reaction to aniline derivatives | 24–48 hours before service |
| Elasticity test | Checks if hair can withstand chemical processing | Before service |
| Porosity test | Determines how well hair will absorb chemicals | Before service |
Emergency Procedures
#### Chemical in the Eye
1. Flush immediately with large amounts of cool water
2. Continue flushing for at least 15–20 minutes
3. Instruct client to seek medical attention
#### Chemical on Scalp/Skin
• Rinse thoroughly with cool water
• If irritation persists, seek medical attention
Safety Data Sheets (SDS)
• Required by law to be on hand for all chemical products in the salon
• Formerly called MSDS (Material Safety Data Sheet)
• Contains:
- Chemical ingredients
- Hazard information
- Safe handling procedures
- First aid measures
- Emergency/spill procedures
- Storage requirements
Key Terms – Safety
• PPE – Personal protective equipment (gloves, apron, eye protection)
• Strand test – Pre-service test for chemical reaction and hair condition
• Patch test – Allergy test for aniline derivatives (24–48 hrs before service)
• SDS (Safety Data Sheet) – Required document listing chemical hazards and handling info
Watch Out For ⚠️
• SDS must be on hand for every chemical product — not just available on request
• For chemical eye contact, flush for a full 15–20 minutes — not just a quick rinse
• The strand test checks the hair's response; the patch test checks the client's skin/allergy response — they are different tests with different purposes
• Gloves are not optional — they are required for all chemical services
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Quick Review Checklist {#checklist}
Use this list to confirm you've mastered the essential exam concepts:
Chemical Concepts
• [ ] Disulfide bonds are broken by chemical services and re-formed during neutralization
• [ ] pH above 7 = alkaline; most chemical services are alkaline
• [ ] Resistant/low porosity hair requires longer processing or heat
Relaxers
• [ ] Sodium hydroxide (lye) relaxers require base cream for scalp protection
• [ ] No-lye relaxers use guanidine hydroxide (guanidine carbonate + calcium hydroxide)
• [ ] NEVER combine sodium hydroxide relaxers with thio relaxers → hair breakage
• [ ] Relaxers are stopped/neutralized with a neutralizing shampoo
Permanent Waves
• [ ] Waving solution breaks disulfide bonds; neutralizer re-forms them
• [ ] Alkaline waves use ATG; process at room temperature; pH 8.2–9.6
• [ ] Acid waves require heat; pH 4.5–7.0
• [ ] Smaller rod = tighter curl; larger rod = looser wave
• [ ] Croquignole = ends to scalp wrap
• [ ] Over-processing = porous, weak, frizzy hair
Hair Color
• [ ] Permanent color requires hydrogen peroxide developer and works in the cortex
• [ ] PPD is the oxidative dye intermediate in permanent color
• [ ] 20-volume developer is standard for gray coverage
• [ ] Complementary colors on the color wheel neutralize each other
• [ ] Patch test required 24–48 hours before any aniline derivative color
• [ ] Lifting = dissolving/removing natural melanin (lightening)
Safety
• [ ] PPE = gloves + apron + eye protection for all chemical services
• [ ] Chemical in eye → flush with cool water for **15