3.2 Basic chemistry & electricity in cosmetology

Chemistry Basics for the Salon

Chemistry is the science that studies the composition, structure, and properties of matter. Matter is anything that occupies space and has mass (weight); it exists in three physical states — solid, liquid, and gas. All matter is built from elements, the simplest forms of chemical matter (about 118 are known), and each element is made of identical atoms. When two or more atoms join, they form a molecule, and a compound (such as water, H₂O) forms when atoms of two or more different elements combine chemically. Cosmetic chemistry has two branches: organic chemistry studies substances that contain carbon (and usually hydrogen), while inorganic chemistry studies matter that does not contain carbon, such as water, metals, and minerals.

Solutions, Suspensions, and Emulsions

Most salon products are physical mixtures, and you should be able to tell the three apart:

• Solution — a stable, uniform blend of a solute dissolved evenly in a solvent (for example, salt water).
• Suspension — larger particles that are spread through a liquid but separate over time, so the product must be shaken (for example, calamine lotion).
• Emulsion — two liquids that normally do not mix, such as oil and water, held together by a surfactant. Oil-in-water (O/W) emulsions feel light; water-in-oil (W/O) emulsions feel heavier and greasier.

Surfactants (surface-active agents) have a water-loving (hydrophilic) head and an oil-loving (lipophilic) tail; this lets them wet surfaces, emulsify, and act as detergents in shampoos. Humectants such as glycerin attract and hold water to keep skin and hair moist, and emollients soften and smooth the surface. Two other groups appear on almost every salon label: silicones, which add slip and shine and help seal the cuticle, and preservatives, which protect a product from bacteria, mold, and yeast so it stays safe to use. Knowing these categories helps you read an ingredient list and predict how a product will behave on the hair or skin.

The pH Scale

pH (potential hydrogen) measures how acidic or alkaline a water-based solution is on a scale of 0 to 14. A pH of 7 is neutral; below 7 is acidic, and above 7 is alkaline. The scale is logarithmic, so each whole number is ten times more acidic or alkaline than the next. Healthy hair and skin are slightly acidic, protected by an acid mantle, with a natural pH of about 4.5 to 5.5. This fact drives many exam questions:

• Acidic products (below about 5.5) tighten and close the cuticle and harden the hair — think of acid-balanced shampoos and conditioners.
• Alkaline products (above 7) soften and swell the hair, raising the cuticle so chemicals can enter. Permanent waves, chemical relaxers, and permanent haircolor all work in an alkaline range.

Oxidation-Reduction (Redox)

Many chemical services depend on redox reactions. Oxidation happens when oxygen is added to a substance (or hydrogen removed), or when a substance loses electrons; a substance that gives off oxygen is an oxidizing agent — the best salon example is hydrogen peroxide, the developer in haircolor and the neutralizer in permanent waving. Reduction happens when oxygen is removed (or hydrogen added), or when a substance gains electrons; thioglycolic acid in permanent-wave solution is a reducing agent that breaks the disulfide bonds of hair. Oxidation and reduction always occur at the same time — one substance is oxidized while the other is reduced. A reaction that releases heat, as oxidation does, is called exothermic.

Electricity, Electrotherapy, and Light

Electricity is a flow of electrons. A material that carries current easily is a conductor (most metals and water); one that resists it is an insulator, or nonconductor (rubber, glass, silk). Current flows only through a complete circuit. Two kinds of current are used in salons, along with the units that measure them:

The main electrotherapy modalities are galvanic current (a constant DC used for desincrustation and for iontophoresis, which drives water-soluble products into the skin by polarity — cataphoresis using the positive pole to soothe and close pores, and anaphoresis using the negative pole to soften tissue and open pores), faradic and sinusoidal currents (alternating currents that cause muscle contractions), and Tesla high-frequency, the "violet ray," a thermal and germicidal current. Safety depends on the fuse, circuit breaker, and GFCI, plus proper grounding and using only UL-listed equipment. In light therapy, both visible and invisible rays are applied to the skin: infrared rays produce heat and relax the skin, while ultraviolet (UV) rays are germicidal but can burn, so exposure limits and eye protection are essential.