Chemistry & Products
About 12% of the California written exam tests how well you understand the products you use every day. You will see questions about pH, hair color categories, peroxide developer volumes, hair relaxers and waves, skin care actives, and the Safety Data Sheets required by Cal/OSHA. You do not need a chemistry degree, but you should know what a product does, why it works, and how to use it safely on your client. This chapter walks through the chemistry you need in plain language with the key California rules cited.
The pH scale and what it means for hair and skin
The pH scale runs from 0 to 14. A value of 7 is neutral (pure water). Anything below 7 is acidic; anything above 7 is alkaline. The scale is logarithmic, so each whole number is a tenfold change in hydrogen ion concentration. Healthy hair and skin sit at about 4.5 to 5.5 (the 'acid mantle'). Most water is roughly pH 7. Permanent waves, relaxers, and lighteners are alkaline, which swells the hair and opens the cuticle; acidic rinses then close it back down.
Shampoo and conditioner chemistry
Shampoos clean using surfactants — molecules with a water-loving end and an oil-loving end. The oil end grabs dirt and sebum, and water rinses everything away. Conditioners are usually slightly acidic and contain cationic (positively charged) ingredients that bind to the negatively charged hair shaft, smoothing the cuticle. Clarifying shampoos use stronger surfactants or chelating agents to remove mineral and product buildup before chemical services. Moisturizing shampoos add humectants and oils for dry hair. pH-balanced shampoos are formulated to about 4.5 to 5.5 to match the hair.
Hair color categories
There are four main categories. Temporary color (rinses, sprays, mascaras) coats only the cuticle and washes out in one or two shampoos. Semi-permanent color is slightly acidic, partly penetrates the cuticle, and fades over 4 to 8 shampoos with no developer. Demi-permanent (deposit-only) color uses a low-volume developer to deposit color without lifting; it fades over 4 to 6 weeks. Permanent (oxidative) color uses 20 vol or higher developer to lighten existing pigment and deposit new color that does not wash out — it grows out instead. The line where new growth meets colored hair is the retouch area.
Hydrogen peroxide developers
Developer is hydrogen peroxide (H2O2) mixed at a known strength. The 'volume' rating tells how many volumes of oxygen gas one volume of developer releases. 10 volume ≈ 3% peroxide, used for deposit-only and toners (no lift). 20 volume ≈ 6%, used with permanent color for gray coverage and 1–2 levels of lift. 30 volume ≈ 9% gives 2–3 levels of lift. 40 volume ≈ 12% is the highest commonly used, for high-lift series — never on the scalp at full strength when the manufacturer warns against it. Always follow the manufacturer's mixing ratio (often 1:1, 1:1.5, or 1:2).
Chemical hair relaxers
Relaxers break and reform the disulfide bonds in the hair cortex to straighten curl. Sodium hydroxide ('lye') relaxers are very alkaline (pH 12–14) and work quickly. They can burn the scalp if left on too long, so timing and base cream protection are critical. Guanidine hydroxide ('no-lye') relaxers are mixed on site from calcium hydroxide and guanidine carbonate. They are gentler on the scalp but can leave mineral deposits that make hair feel dry. After processing, a neutralizing shampoo lowers the pH and stops the chemical reaction.
Permanent waves
A perm reshapes the disulfide bonds in the cortex. The hair is wrapped on rods, then waving lotion (a reducing agent) breaks the bonds. Cold (alkaline) waves use ammonium thioglycolate (ATG) at pH 8.5–9.5 and process at room temperature. Acid waves use glyceryl monothioglycolate at lower pH with mild heat, giving a softer curl that is gentler on color-treated hair. After the desired curl forms, a neutralizer (usually hydrogen peroxide) is applied. This oxidizes and re-forms the disulfide bonds in the curled position. The neutralizing step is chemically an oxidation reaction.
Skin care actives
Alpha hydroxy acids (AHAs) like glycolic and lactic acid are water-soluble and exfoliate the surface of the stratum corneum, smoothing texture and brightening. Beta hydroxy acid (BHA / salicylic acid) is oil-soluble, penetrates pores, and is favored for oily and acne-prone skin. Retinoids (vitamin A derivatives) increase cell turnover and stimulate collagen — strong but can cause dryness and sun sensitivity. Sunscreen is essential daily. SPF measures protection against UVB (sunburn); look for 'broad-spectrum' for UVA (aging) protection. Always patch test new actives and document on the client card.
Hair porosity, texture, and chemical service selection
Porosity is how easily hair absorbs moisture and chemicals. Low-porosity hair has tightly packed cuticles that resist penetration and may need longer processing or a presoftener. High-porosity hair (often damaged or very curly) absorbs and releases chemicals quickly, so use the lowest effective product strength and watch the timer closely. Texture (fine, medium, coarse) and density also matter: fine hair processes faster; coarse hair may need stronger products or more time. Always evaluate elasticity — hair that does not return to shape when stretched is too damaged for a chemical service.
Safety Data Sheets and hazard communication
Cal/OSHA's Hazard Communication Standard (8 CCR §5194) requires every California salon to keep a Safety Data Sheet (SDS) for each hazardous chemical used in the workplace. SDSs follow the 16-section Globally Harmonized System (GHS) format. Key sections to know: Section 1 (identification), Section 2 (hazards), Section 4 (first-aid measures — what to do for eye splashes, ingestion, etc.), Section 8 (personal protective equipment), and Section 13 (disposal). SDSs must be available to employees at all times during their shift, not locked in a manager's office. Train new staff before they first handle the product.
Storage, disposal, and California nail chemistry rules
16 CCR §979 requires that all salon products be properly labeled, stored in clean, dry areas separated from food, and kept in closed containers when not in use. Leftover chemicals must be disposed of according to the SDS and local hazardous-waste rules — not poured down storm drains. For nail services, Business and Professions Code §7315 prohibits the use of methyl methacrylate (MMA) liquid monomer on clients. Ethyl methacrylate (EMA) is the legal alternative. Keep flammable liquids (acetone, alcohol) away from heat sources and follow ventilation requirements for nail and chemical service stations.