2.5 Chemistry for Cosmetology

Cosmetology State Board Exam Exam

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1 Introduction to the Cosmetology State Board Exam

1.1 About the Cosmetology State Board Exam 1.2 NIC vs State-Specific Exams 1.3 Exam Content Breakdown 1.4 How to Register and What to Expect 1.5 How to Use This Study Guide

2 Chapter 2: Scientific Concepts (35% of NIC Exam)

2.1 Infection Control & Sanitation 2.2 Bacteriology 2.3 Anatomy & Physiology - Skin 2.4 Anatomy & Physiology - Hair & Nails 2.5 Chemistry for Cosmetology 2.6 Electricity & Safety

3 Hair Care and Services

3.1 Hair Analysis and Consultation 3.2 Shampooing and Conditioning 3.3 Haircutting Fundamentals 3.4 Hairstyling and Finishing 3.5 Chemical Texture Services 3.6 Hair Coloring

4 Skin Care & Esthetics

4.1 Skin Analysis & Consultation 4.2 Facial Treatments 4.3 Hair Removal 4.4 Makeup Application

5 Chapter 5: Nail Care

5.1 Nail Anatomy & Disorders 5.2 Manicure Services 5.3 Pedicure Services 5.4 Nail Enhancements 5.5 Nail Art & Finishing

6 Chapter 6: State Licensing Requirements

6.1 How State Licensing Works 6.2 Training-Hour Requirements Across States 6.3 Exam Components: Theory and Practical 6.4 Application, Background Checks & Fees 6.5 Reciprocity, Endorsement & License Transfer 6.6 Renewal and Continuing Education 6.7 Scope of Practice & License Types 6.8 State Sanitation Rules & Discipline 6.9 Multi-State Comparison & Relocation Guide

7 Chapter 7: New York Cosmetology Exam

7.1 About the New York Cosmetology Exam 7.2 New York State Laws & Regulations 7.3 NY Written Exam Content 7.4 NY Practical Exam 7.5 NY-Specific Practice Questions

8 Chapter 8: Florida Cosmetology Exam

8.1 About the Florida Cosmetology Exam 8.2 Florida State Laws & Regulations 8.3 Florida Salon Requirements 8.4 FL Theory Exam Content 8.5 FL Clinical Exam Content 8.6 FL-Specific Practice Questions

9 Chapter 9: Test Strategies

9.1 Test-Taking Strategies 9.2 Preparing for the Written Exam 9.3 Preparing for the Practical Exam 9.4 Exam Day Checklist 9.5 Comprehensive Practice Questions 9.6 Final Review Checklist

2.5 Chemistry for Cosmetology

Key Takeaways Explain This Topic AI

The pH scale ranges from 0-14: acidic (0-6.9), neutral (7), alkaline (7.1-14).

Hair and skin have a natural pH of 4.5-5.5 (slightly acidic).

Alkaline products (perms, relaxers, color) swell and open the hair cuticle.

Acidic products close and harden the cuticle, adding shine.

Relaxers are the most alkaline products (pH 12-14), requiring extreme care.

Last updated: January 2026

Chemistry is fundamental to understanding how cosmetology products work. The pH scale, oxidation reactions, and chemical bonding are essential concepts for safe and effective salon services.

The pH Scale

pH (potential hydrogen) measures how acidic or alkaline a substance is. Understanding pH is critical because it determines how products affect hair and skin.

Loading diagram... The pH Scale in Cosmetology

pH Scale Overview

• pH Level Classification Effect on Hair
• 0-6.9 Acidic Closes cuticle, hardens, adds shine
• 7 Neutral Balanced, no change
• 7.1-14 Alkaline Opens cuticle, softens, swells shaft
• Natural pH Levels

• Substance pH Level
• Hair 4.5-5.5
• Skin 4.5-5.5
• Nails 4.5-5.5
• Water 7 (neutral)
• Blood 7.35-7.45
• pH of Common Salon Products

• Product pH Range Effect
• Hydrogen Peroxide 2.5-4.5 Acidic, oxidizing
• Acid-Balanced Shampoo 4.5-5.5 Maintains natural pH
• Permanent Wave (Acid) 6.5-7.0 Gentle, heat-activated
• Permanent Wave (Alkaline) 9.0-9.6 Stronger, no heat needed
• Permanent Hair Color 9.5-10.5 Alkaline to lift/deposit
• Lighteners/Bleach 8.5-10.5 Alkaline to lift color
• Hydroxide Relaxers 12-14 Very alkaline, strong
• Acids vs. Alkalis in Products
• Acidic Products (pH below 7)

Effects on Hair:

• Close and compact the cuticle layer
• Harden the hair shaft
• Add shine and smooth texture
• Lock in color after chemical services

Common Acidic Products:

• Conditioners
• Finishing rinses
• Color sealers
• Acid perms
• Alkaline Products (pH above 7)

Effects on Hair:

• Open and lift the cuticle
• Soften and swell the hair shaft
• Allow penetration of chemicals
• Enable color deposit or bond breaking

Common Alkaline Products:

• Permanent hair color
• Lighteners (bleach)
• Alkaline perms
• Relaxers
• Clarifying shampoos
• The Cuticle Response

Loading diagram... How pH Affects the Hair Cuticle

• Chemistry of Hair Color
• Oxidation in Hair Coloring

Hair color chemistry relies on oxidation - a chemical reaction that occurs when developer (hydrogen peroxide) mixes with color.

• How Permanent Hair Color Works
• Alkaline color opens the cuticle (allows penetration)
• Developer breaks down natural melanin (lightening)
• Oxidation develops artificial pigment (new color)
• Color molecules enlarge inside cortex (permanent deposit)
• Developer (Hydrogen Peroxide) Volumes

• Volume Strength Lifting Power Common Use
• 10 Volume (3%) Lowest Deposit only Darker shades, toning
• 20 Volume (6%) Standard 1-2 levels Most permanent color
• 30 Volume (9%) Stronger 2-3 levels High-lift colors
• 40 Volume (12%) Strongest 3-4 levels Lightening, with caution
• Color Types

• Type pH Penetration Duration
• Temporary Acidic Cuticle only Washes out
• Semi-Permanent Slightly acidic Cuticle 4-6 shampoos
• Demi-Permanent Slightly alkaline Cuticle/outer cortex 6-12 shampoos
• Permanent Alkaline (9-10.5) Cortex Until cut off
• Chemistry of Permanent Waves
• How Perms Work

Permanent waves restructure the hair's internal bonds to create curl patterns.

• The Chemical Process
• Waving lotion (reducing agent) breaks disulfide bonds
• Hair is wrapped around rods in new shape
• Bonds reform in new curl pattern
• Neutralizer (oxidizing agent) re-hardens and locks bonds

Loading diagram... The Permanent Wave Process

Types of Permanent Waves

• Type Active Ingredient pH Heat Required Best For
• Alkaline (Cold Wave) Ammonium thioglycolate 9.0-9.6 No Normal, resistant hair
• Acid Wave Glyceryl monothioglycolate 6.5-7.0 Yes Fine, damaged, color-treated
• Exothermic Self-heating 9.0-9.6 Self-generates Resistant hair
• Thio-Free Cysteamine or sulfites Varies Varies Sensitive scalps
• Key Chemistry Terms
• Reducing Agent : Breaks disulfide bonds (waving lotion)
• Oxidizing Agent : Reforms and hardens bonds (neutralizer)
• Disulfide Bonds : Strong bonds giving hair its shape
• Processing Time : Time needed for chemical action
• Chemistry of Relaxers

Relaxers straighten curly hair by permanently breaking and reforming bonds.

Types of Relaxers

• Type Active Ingredient pH Strength
• Sodium Hydroxide (Lye) NaOH 12-14 Strongest
• Calcium Hydroxide (No-Lye) Ca(OH)2 12-14 Strong, less irritating
• Guanidine Hydroxide Mixed components 13+ Strong
• Thio Relaxer Ammonium thioglycolate 9.0-9.6 Milder
• How Relaxers Work
• Hydroxide ions break disulfide bonds
• Bonds convert to lanthionine bonds (cannot be reversed)
• Hair is smoothed and rinsed
• Neutralizing shampoo restores pH

Critical Safety Note: Hydroxide relaxers cause a permanent chemical change called lanthionization. This process CANNOT be reversed. Hair cannot be permed after hydroxide relaxer treatment.

• Product Safety
• Patch Testing

Always perform a patch test before:

• Hair color services
• Chemical treatments on new clients
• Any product the client hasn't used before

Procedure:

• Apply small amount behind ear or inner elbow
• Wait 24-48 hours
• Check for redness, swelling, itching
• Chemical Safety Guidelines

• Practice Reason
• Read manufacturer's directions Proper use ensures safety
• Wear gloves during chemical services Protect skin from irritation
• Never mix incompatible products Dangerous reactions possible
• Check scalp for abrasions before services Prevent chemical burns
• Time processes accurately Prevent overprocessing damage
• Perform strand tests Determine proper timing
• Incompatible Chemicals

Never combine:

• Hydroxide relaxers and thio products
• Metallic salts and oxidizing color
• Different brand chemical systems (unless verified compatible)