WA Cosmetology key terms

The middle and thickest layer of a hair strand, made of elongated keratinized cells. It holds the pigment melanin and gives hair its strength, elasticity, and natural curl pattern.

The ability of hair to absorb and hold moisture, determined by how tightly the outer cuticle scales lie. Low porosity resists moisture, while high porosity absorbs quickly and loses it just as fast.

The ability of hair to stretch and return to its original length without breaking. Healthy wet hair stretches noticeably; poor elasticity signals weak, overprocessed, or damaged hair.

The active growth phase of the hair cycle, when cells divide in the follicle and the strand lengthens. It is the longest phase and determines how long a client's hair can grow.

The natural direction in which hair grows out from the scalp, sometimes forming a whorl at the crown. Cutters follow the stream so the finished shape does not gap or stand up.

The angle at which a section of hair is held away from the head while cutting, also called projection. A low angle builds weight; a high angle creates layers and removes bulk.

Combing a section of hair away from its natural falling position before cutting, usually to blend lengths toward a guide. It creates graduation and keeps weight where the client wants it.

The amount of pull applied to hair while cutting, combing, or wrapping. Even tension keeps sections level; stretching the hair too much makes the finished cut come out uneven.

Dividing the head into manageable areas with partings and clips before cutting, coloring, or styling. Consistent sections keep the work organized and help results balance on both sides.

A cut made with zero elevation so every hair in a section falls to a single length, creating a solid straight edge. It produces a firm perimeter and maximum weight at the ends.

A cut in which lengths build from shorter at the perimeter to longer at the crown, created by cutting at low to medium elevation. Also called a wedge or stack.

A small amount of product applied to skin, usually behind the ear or in the elbow crease, 24 to 48 hours before a color service to check for an allergic reaction.

A hydrogen peroxide solution that supplies oxygen during a color service, working with the dye to lighten natural pigment and deposit new color. Its strength, or volume, controls lift and deposit.

The degree of lightness or darkness of a hair color, measured on a scale from 1 for black to about 10 or 12 for the lightest blonde. Level describes value, not warmth or coolness.

The warmth or coolness of a color, described as warm, neutral, or cool. Tone is separate from level and is chosen to balance the underlying pigment already in the hair.

A scale from 0 to 14 that measures how acidic or alkaline a substance is, with 7 as neutral. Hair and scalp prefer slightly acidic products; high-pH products swell and open the cuticle.

An alkaline cream that breaks disulfide bonds in the hair so it can be straightened, usually at a pH between about 9 and 10. A neutralizer is applied afterward to rebuild the bonds.

A strong alkaline relaxer, often a no-lye formula, that straightens hair permanently by breaking disulfide bonds. It is not neutralized chemically; it is rinsed out and the hair rebalanced with an acidic shampoo.

A product used after a thio relaxer or a perm that stops the chemical action and rebuilds the disulfide bonds in their new shape, usually with an oxidizing agent such as hydrogen peroxide.

Coloring only selected strands of hair by weaving or slicing them and applying lightener, creating contrast with the rest of the hair. Foils or a cap keep treated strands separated.

An oily substance made by the sebaceous glands that lubricates skin and hair and helps form the acid mantle. Overproduction is linked to oily skin, oily scalp, and clogged pores.

The outermost protective layer of the skin, built from cells that contain no blood vessels. It holds the melanocytes that make pigment and is the layer most affected by surface treatments.

The deeper layer of the skin, containing nerves, blood vessels, hair follicles, and glands. It supports the epidermis and is where most of the structures an esthetician treats are located.

Removing dead cells from the skin's surface with scrubs, brushes, or chemical agents such as alpha hydroxy acids. It smooths texture, brightens the skin, and helps products absorb.

Removing blackheads, comedones, or milia from the skin by pressing gently around the follicle. It is done only on non-inflamed skin, with clean hands and properly disinfected tools.

The visible hard plate of keratin that covers and protects the nail bed. It is formed in the matrix and its free edge extends beyond the fingertip.

The living area at the base of the nail where new cells form and harden into the nail plate. Injury or disease here permanently changes the shape or thickness of the nail.

The whitish half-moon area at the base of the nail plate where the matrix shows through. It looks lighter because those cells are not yet fully keratinized and is most visible on the thumbs.

The living fold of skin at the base of the nail plate that seals the gap between nail and skin. Often mistakenly called the cuticle, it should never be cut with nippers.

The skin beneath the free edge of the nail plate, where the nail separates from the fingertip. It seals the nail bed against dirt, water, and infection.

Bacteria that can cause disease or infection in humans. In the salon they are the main reason for handwashing, clean implements, and disinfecting tools between every client.

Destroying most harmful microorganisms on surfaces and implements using an EPA-registered, hospital-grade product mixed and used exactly as its label directs. It does not kill all bacterial spores.

Destroying all microbial life, including bacterial spores, usually with an autoclave using heat and pressure. Most salons need it only for items that penetrate or cut the skin.

Microorganisms carried in blood that can cause disease, such as hepatitis B and HIV. Salons must follow OSHA rules and handle any bleeding incident with gloves and proper disinfection.

A document from a product manufacturer that lists a chemical's hazards, first aid, handling, storage, and spill information. It must be kept accessible to employees in the salon.

Moving microorganisms from one person or object to another, often by using the same tool, towel, or product on two clients. Single-use items and freshly cleaned implements prevent it.

Treating all blood, body fluids, and potentially infectious materials as if they carry disease. The rule applies to every client and every cleanup task, not only to known carriers.

An infestation of head or body lice, which spreads easily through shared combs, brushes, and linens. Service is refused, the client is referred out, and implements and linens are cleaned and disinfected.

Fitting tools, equipment, and work positions to the body to reduce strain and injury. Correct posture, an adjustable chair, and properly sized shears help prevent fatigue and repetitive strain.