5.3 Product Chemistry, pH & Safety Testing (Patch/Strand)

Product Chemistry, pH, and Safety Testing

In barbering, every chemical application requires an understanding of chemical compounds and how they interact with human tissue. Barbers must master the pH scale, understand the formulation of common salon products, and follow strict safety testing protocols to protect clients from injury and allergic reactions.

The pH Scale and Hair/Skin Chemistry

The term pH stands for potential hydrogen. The pH scale measures the acidity or alkalinity of water-soluble substances. It ranges from 0 to 14, with 7 being neutral (e.g., pure distilled water).

• Acidic Solutions: Have a pH below 7. Acidic products help to close, contract, and shrink the hair cuticle.
• Alkaline Solutions: Have a pH above 7. Alkaline products cause the hair shaft to swell, softening and opening the cuticle layer so that chemicals can penetrate the cortex.

The Logarithmic Nature of pH

The pH scale is logarithmic, meaning that each step on the scale represents a tenfold increase or decrease in acidity or alkalinity. For example:

• A pH of 6 is 10 times more alkaline than a pH of 5.
• A pH of 7 is 100 times more alkaline than a pH of 5.
• A pH of 8 is 1,000 times more alkaline than a pH of 5.

Because of this rapid exponential change, even a minor shift in pH can have a dramatic physical effect on the hair structure. The natural pH of hair, skin, and the scalp is slightly acidic, ranging between 4.5 and 5.5. Barbers must use products that respect or help restore this natural pH range to prevent dryness, irritation, and hair breakage.

Chemical Makeup of Barbering Products

Shampoos

Shampoos are designed to cleanse the hair and scalp. The primary ingredient in most shampoos is water, followed by surfactants (surface active agents). A surfactant molecule consists of two parts:

1. Hydrophilic Head: The water-loving head that attracts water.
2. Lipophilic Tail: The oil-loving tail that attracts dirt, sebum, and oils.

When shampooing, the lipophilic tail binds to the oils on the hair, and the hydrophilic head binds to the water, allowing the dirt and oil to be rinsed away. Shampoos are formulated to target specific hair conditions:

• pH-Balanced Shampoos: Formulated to have the same pH as hair and skin (4.5 to 5.5). They prevent excessive swelling of the cuticle.
• Clarifying Shampoos: Contain active chelating agents and have a higher, more alkaline pH to strip away styling product buildup and mineral deposits. They should not be used daily.
• Conditioning Shampoos: Infused with protein or moisturizing agents to restore moisture and elasticity while cleansing.

Conditioners

Conditioners are physical mixtures designed to deposit protein or moisture to restore the hair’s strength and close the cuticle. They contain:

• Humectants: Substances that absorb and retain moisture from the surrounding air.
• Emollients: Softening agents that smooth the cuticle and reduce friction.
• Silicones: Form a reflective barrier to add shine and protect the hair shaft from heat styling.

Styling Aids

• Pomades: Historically oil-based, modern pomades are often water-soluble and contain heavy emollients to provide shine and pliable hold.
• Hair Gels: Water-based products containing polymers that form a stiff, protective coating over the hair fibers, locking them in place.
• Hairsprays: Alcohol-based styling aids containing resins that dry quickly to hold finished styles.

The Predisposition (Patch) Test

The Federal Food, Drug, and Cosmetic Act mandates that a predisposition test, commonly called a patch test, must be performed on every client before using any hair color product containing an aniline derivative tint.

Purpose and Timelines

The patch test identifies if a client is allergic or hypersensitive to aniline derivatives, which are known sensitizing agents that can cause contact dermatitis, swelling, and severe allergic reactions. The test must be administered 24 to 48 hours prior to the service.

Proper Locations and Procedure

1. Locations: The test must be conducted either behind the ear or in the inner fold of the elbow (inner elbow).
2. Method:
   • Cleanse the test area (behind ear or inner elbow) with mild soap and water, then pat dry.
   • Mix a small, equal part of the exact hair color shade and developer to be used.
   • Apply a small drop of the mixture to the prepared test site using a sterile cotton swab.
   • Instruct the client to leave the test area uncovered and dry for 24 to 48 hours.
3. Evaluation:
   • Negative Result: No signs of redness, inflammation, itching, burning, swelling, or welts. The service is safe to perform.
   • Positive Result: Any sign of redness, burning, itching, or swelling. Do not perform the service; advise the client to consult a physician.

The Preliminary Strand Test

While the patch test checks for systemic allergies, the preliminary strand test evaluates the hair’s physical properties and how it will react to the chemical formulation.

Elements Tested

• Color Development: Reveals the final color result and processing time.
• Porosity: Evaluates how quickly the hair absorbs the chemical. Highly porous hair absorbs product rapidly but can over-process.
• Elasticity: Evaluates the hair's internal strength. If a strand stretches and breaks, aggressive chemical treatments must be avoided.
• Compatibility: Verifies if previous treatments, like metallic salts or henna, are present. If incompatible substances are present, the hair may smoke, bubble, or break.

Procedure

Select a small section of hair (about 20-30 strands) in a discreet area, such as the lower crown or nape. Apply the mixed chemical formula, monitor the processing time, rinse with warm water, dry, and inspect the structural integrity and color.