2.3 Basic Chemistry, pH, and Product Chemistry

Section 2.3: Basic Chemistry, pH, and Product Chemistry

Understanding chemistry is vital for barbers because every product used in the shop—from water to hair color—is a chemical. Knowing how chemicals react protects the barber and customer, ensures proper product selection, and guarantees that chemical services achieve the desired results without causing hair breakage or scalp burns.

Matter, Properties, and Chemical Changes

Matter is any substance that occupies space and has physical and chemical properties. Matter exists in three physical states: solid, liquid, and gas. Every substance has unique properties:

• Physical Properties: Characteristics that can be determined without a chemical reaction and do not involve a chemical change in the identity of the substance. These include color, odor, weight, density, melting point, boiling point, and hardness.
• Chemical Properties: Characteristics that can only be determined by a chemical reaction and a chemical change in the identity of the substance. Examples include the ability of iron to rust, hair to burn, or wood to decompose.

Matter can undergo physical or chemical changes:

• Physical Change: A change in the form or physical properties of a substance without a chemical reaction or the creation of a new substance. For example, ice melting into water, or mixing temporary hair color with water.
• Chemical Change: A change in the chemical composition of a substance, creating a new substance with different properties. For example, oxidation, which occurs when permanent hair color is mixed with hydrogen peroxide developer, or the curling process of a perm.

All matter is composed of elements, which cannot be broken down into simpler substances. The smallest unit of an element is an atom. When two or more atoms combine chemically, they form a molecule.

• Elemental Molecule: Formed by combining atoms of the same element (e.g., oxygen (O2)).
• Compound Molecule: Formed by combining atoms of different elements (e.g., water (H2O), or sodium chloride (NaCl)).

Oxidation-Reduction (Redox) Reactions

An important type of chemical reaction in barbering is oxidation-reduction (redox). Oxidation is a chemical reaction that combines a substance with oxygen to produce an oxide.

• Oxidizing Agent: A substance that releases oxygen. Hydrogen peroxide is a common oxidizing agent used in hair developer.
• Reducing Agent: A substance that adds hydrogen to a chemical compound or subtracts oxygen from it. In permanent waving, the waving lotion acts as a reducing agent to break disulfide bonds.
• Exothermic Reactions: Chemical reactions that produce heat. Many permanent waves and certain hair lighteners undergo exothermic reactions, which require careful monitoring to prevent scalp injury.

Solutions, Suspensions, and Emulsions

Barbering products are physical mixtures of substances, categorized based on how their ingredients are distributed.

An emulsion is formed using a surfactant (surface-active agent). Surfactant molecules have two parts:

1. Hydrophilic Head: The water-loving head that dissolves in water.
2. Lipophilic Tail: The oil-loving tail that dissolves in fats and oils.

Emulsions are classified as:

• Oil-in-Water (O/W) Emulsions: Oil droplets emulsified in water. They feel less greasy and are easily rinsed off. Most grooming creams and hair conditioners are O/W emulsions.
• Water-in-Oil (W/O) Emulsions: Water droplets emulsified in oil. They feel greasier and are water-resistant. Examples include cold creams and styling pomades.

The pH Scale and Acid-Alkali Balance

The term pH stands for potential hydrogen, representing the concentration of hydrogen ions in an aqueous (water-based) solution. Only solutions containing water can have a pH. The pH scale ranges from 0 to 14:

• pH 7: Neutral (e.g., pure distilled water).
• pH below 7: Acidic. Acidic solutions have a high hydrogen ion concentration.
• pH above 7: Alkaline. Alkaline solutions have a low hydrogen ion concentration.

The Acid Mantle and Hair Chemistry

The natural pH of human hair and skin is slightly acidic, falling between 4.5 and 5.5. This is maintained by the acid mantle, a protective barrier of sebum and sweat.

• Acids (pH below 7): Mild acids contract, harden, and shrink the hair cuticle. Barbers use acidic conditioners (pH 3.0 to 4.5) to close the cuticle after chemical treatments.
• Alkalis (pH above 7): Alkalis soften, swell, and open the hair cuticle, allowing chemicals to penetrate the cortex. Products like chemical hair relaxers (pH 11.5 to 14.0) and permanent waves (pH 9.0 to 9.6) are highly alkaline.

The Logarithmic Rule: The pH scale is logarithmic. This means each step represents a tenfold change. A pH of 8 is 10 times more alkaline than neutral water (pH 7), but a pH of 9 is 100 times more alkaline (10 x 10). A pH of 12 (relaxer) is 100,000 times more alkaline than a pH of 7, making it highly corrosive if left on the skin.

Chemical Bonds in Hair

The hair cortex is composed of polypeptide chains held together by three types of side bonds:

• Hydrogen Bonds: Weak, physical side bonds that are easily broken by water or heat. They reform as the hair dries or cools, allowing for temporary styling (such as blow-drying or roller sets).
• Salt Bonds: Weak, physical side bonds that are broken by changes in pH. They reform when the pH of the hair is restored to its natural state.
• Disulfide Bonds: Strong, chemical side bonds that cannot be broken by water or heat. They can only be broken by chemical agents, such as perm solutions or hair relaxers. Reforming these bonds through neutralization alters the hair’s shape permanently.

Cosmetic Ingredients in Barbering Products

Barbers utilize various products formulated for specific hair and skin needs:

• Shampoos: Formulated with water and surfactants to cleanse. Clarifying shampoos contain active chelating agents to remove mineral and product buildup. Medicated shampoos contain anti-fungal ingredients (like pyrithione zinc) to treat dandruff.
• Conditioners: Formulated to deposit protein or moisture to restore hair strength and manageability. They contain humectants (substances that promote retention of moisture) and silicones to add shine.
• Astringents and Toners: Used after shaving to tighten the skin. Astringents have a lower pH and a higher alcohol content (up to 30%) to constrict pores.
• Shaving Creams: Formulated to soften the beard hair and provide lubrication for the razor blade. They contain potassium hydroxide to maintain alkalinity, which swells the hair shaft for an easier cut.