7.2 The pH Scale, Overexposure, and Chemical Burns

Why pH and chemical injury sit in the same Domain 1.C bucket

Quick Answer: pH tells you whether a product is acid or alkaline relative to 7. Textbook hair and skin sit near 4.5–5.5. Alkaline waves and hydroxide relaxers are much more alkaline so they swell the cuticle and attack disulfide bonds. When pH, time, or concentration goes past what the fiber or skin can tolerate, the same chemistry becomes overexposure or a chemical burn. N.J.A.C. 13:28-6.29 budgets 30 class hours for this science; N.J.A.C. 13:28-3.2 still ties disinfectant kill time to an EPA-registered tuberculocidal product's label (or an FDA-registered autoclave), not to a Board-invented pH or minute table.

NIC New Jersey Domain 1.C names chemical reactions that include overexposure and chemical burn in the same family as product purpose and pH. That is not accidental. A sodium hydroxide relaxer that is correctly mixed is still a caustic alkali. A 40-volume developer that is correctly labeled is still a strong oxidizer. The exam asks whether you can predict tissue and hair response from pH and then stop the reaction the way the SDS and manufacturer say to stop it.

The pH scale: acid, neutral, alkaline

pH measures hydrogen-ion concentration on a scale of 0 to 14. 7 is neutral (pure water at standard teaching conditions). Below 7 is acidic. Above 7 is alkaline (also called basic). The scale is logarithmic: a move from pH 6 to pH 5 is a tenfold increase in hydrogen ions, not a one-point nudge. pH 5 to pH 4 is another tenfold. That is why a relaxer a few units above hair pH is not “a little stronger”; it is orders of magnitude more alkaline.

Acids in salon use contract and harden the cuticle when used as acid-balanced finishes (many conditioners and some rinses). Alkalis soften and swell the cuticle. Swelling is useful when you need the cortex (color, perm, relaxer). Swelling is harmful when it is uncontrolled: mushy, overly porous hair and chemical burns on skin.

New Jersey Board rules do not assign a legal pH number that every color or relaxer must meet. Do not memorize a fake N.J.A.C. pH cap. Compare products to the textbook acid mantle and then read the SDS and label for that SKU.

Textbook pH of hair and skin, and why chemical texture is high pH

Standard cosmetology teaching places hair, skin, and the acid mantle near pH 4.5–5.5. That slightly acid film helps the cuticle lie flatter and supports a normal barrier. Water at 7 is already more alkaline than hair. A typical alkaline perm using ammonium thioglycolate is taught in the high 9s (often cited near 9.0–9.6 on manufacturer and textbook charts). Hydroxide relaxers are taught in the low-to-mid 12s to about 13+. Those figures are textbook/product ranges, not New Jersey statutes. If a quiz stem gives a label pH, use the label.

Why are relaxers and (alkaline) perms high pH? Disulfide bonds live in the cortex, under the cuticle. An alkali raises pH, swells the fiber, and lets the reducing agent (thio) or hydroxide reach those bonds. If you applied a true acid at skin pH, the cuticle would stay compact and the service would not process as designed. Acid-balanced perms (often glyceryl monothioglycolate) sit nearer neutral to slightly acid on textbook charts and usually need heat to process; they are still chemical waves, not a shampoo.

Again: ranges in this table are teaching values. A New Jersey inspector does not carry a secret Board pH list. A Prometric item will expect the acid-mantle number, the meaning of 7, and why chemical texture is alkaline, not a fabricated N.J.A.C. clause.

Neutralization: two different chemical stories

Thio permanent wave or thio relaxer: after rinsing waving lotion, you apply an oxidizing neutralizer. Oxidation rebuilds disulfide bonds in the new shape. Stopping early leaves bonds open (weak, too curly or too straight, breakage). The water rinse before neutralization removes excess ATG so the oxidizer is not wasted fighting leftover reducer. pH comes down as you rinse and use acid-balanced products, but the bond chemistry is the oxidizer, not a splash of vinegar.

Hydroxide relaxer: there is no disulfide rebuild. Neutralizing shampoo after a hydroxide relaxer is primarily pH restoration and thorough removal of alkali. Calling it the same step as perm neutralization is a classic fail. You still must stop the alkali on hair and skin: complete processing, complete rinse, acid-balanced shampoo as the line directs, and never follow with a thio perm.

Acid–alkali neutralization in a beaker (acid + base → salt + water + heat) is why you do not pour a random acid onto a relaxer burn unless the SDS first-aid section says to. Heat from a neutralization reaction on already burned skin can worsen injury. Copious water is the default first action for most salon chemical splashes until SDS or emergency personnel say otherwise.

Overexposure

Overexposure means the body or the hair received too much chemical relative to tolerance: too concentrated, too long, too frequent, or on a compromised barrier (abraded scalp, overlapping lightener, prior hydroxide, uncovered skin). A product can be legal, labeled, and mixed correctly and still overexpose a client if you ignore strand tests, timing, porosity, or retouch-only maps.

Examples in a New Jersey chemical service:

• Leaving hydroxide relaxer on past the strand-test time because the rod pattern “isn’t quite straight.”
• Applying 40-volume on a thin, porous head that needed 20-volume.
• Repeating oxidative color weekly on the same lengths until the cuticle is dissolved.
• Wearing no gloves while mixing lightener so the same alkali and peroxide dose your hands all day (practitioner overexposure).
• Reusing disinfectant past the label reuse period so the chemical is too weak (under-exposure of the microbe, which is the opposite problem, but still a label-concentration error).

Sensitization is a related reaction: repeated contact produces allergy (often to hair dye intermediates). That is why predisposition / patch testing belongs with color procedures; chemistry explains why a second exposure can be worse than the first.

Chemical burns

A chemical burn is tissue damage from a corrosive or irritant reaction, not from a curling iron. Sodium hydroxide relaxer on a scalp with nicks, high-pH depilatory on damp skin left too long, undiluted disinfectant on hands, and peroxide on broken skin are typical salon mechanisms. Alkalis often feel soapy and deep; they can keep destroying tissue until diluted and removed. Acids may hurt immediately. Either can involve the eye.

Immediate professional response, aligned with SDS teaching:

1. Stop the service. Remove saturated cotton, drape, or gloves that are holding product on skin.
2. Rinse with large amounts of lukewarm water. For eyes, rinse continuously (emergency teaching commonly cites 15 minutes or SDS-specified time) and seek medical care. Do not tell the client to “blink it out.”
3. Do not neutralize a skin burn with a kitchen acid or leftover perm neutralizer unless Section 4 of the SDS (first aid) directs that specific action.
4. Document and follow blood-contact / medical-referral judgment if the barrier is broken. Chemistry does not turn you into a physician; it tells you not to keep processing.

Prevention is pH-aware procedure: base cream on hairline and ears for hydroxide, dry hair as the relaxer line requires, gloves, immediate wipe of drips, strand timing, and no double-processing incompatible chemistries from 7.1.

SDS, PPE, and New Jersey disinfectant contact time

The Occupational Safety and Health Administration (OSHA) Hazard Communication Standard requires Safety Data Sheets for hazardous chemicals in the workplace. Modern SDS documents use a 16-section format. For this exam, know where to look: identification, hazards, composition, first-aid (Section 4), firefighting, spill, handling/storage, exposure controls / PPE (Section 8), physical properties including pH, and stability/reactivity (incompatible mixtures—thio with hydroxide, bleach with ammonia).

Personal protective equipment (PPE) for New Jersey chemical services typically includes chemical-resistant gloves (nitrile is widely used for color and relaxer; check SDS), cape and towels as draping chemistry (keep product off skin), eye protection when mixing powders and developers, and apron. PPE is not optional fashion; it is how you avoid practitioner overexposure while you still hit N.J.A.C. 13:28-3.2 on the disinfection side.

N.J.A.C. 13:28-3.2 requires sanitizing implements with an EPA-registered chemical disinfectant used for the contact time specified on the product label. That contact time is a chemical reaction clock against listed organisms. Wiping the product off in 30 seconds because the pH “feels strong” is not compliance. The Board did not replace labels with a single New Jersey minute or pH figure. Mix disinfectant at the labeled dilution, keep surfaces wet for the listed time, and store chemicals so incompatible products (for example ammonia-containing waste and hypochlorite) are not poured together.

Domain 1.C in one sentence: know what the ingredient is for, how it interacts, where it sits on the pH scale, and how overexposure and burns are stopped—then apply that same discipline to color, relaxer, perm, and the disinfectant jar.