CO Cosmetology cheat sheet

Hair growth cycle: anagen (active growth, roughly 2-6 years on the scalp), catagen (transition, about 2-3 weeks), telogen (rest, about 3 months); shedding follows telogen.

Beard hair is coarser and more elliptical in cross-section than scalp hair, so it resists cutting and needs a sharper blade with a lower cutting angle.

Straight razor shaving: lather against the grain to lift hair, shave with the grain first; hold the blade at about 30 degrees and stretch skin taut to prevent nicks.

Fade structure: the guide line is established at the lowest clipper setting, then guards are blended upward in overlapping strokes; each higher guard must overlap the previous zone by roughly half its length.

Clipper-over-comb uses the comb as a barrier: comb lifts hair perpendicular to the scalp, clipper cuts only the hair protruding through the teeth, working from nape upward.

Tapered neckline: the finished line sits at or just above the natural hairline; a blunt line below the hairline shortens the neck and looks unfinished as it grows out.

Disinfection vs sterilization: implements contacting blood or broken skin require an EPA-registered hospital disinfectant at label contact time; porous items that cannot be disinfected are single-use.

Tension and elevation govern shape: 0 degrees builds weight, 45 degrees layers, 90 degrees uniform layers, 180 degrees long layers; a 45-degree cut with vertical sections creates graduation.

pH scale: hair is about 4.5-5.5; shampoo near 5.5; permanent waves and relaxers run pH 9-13; the disulfide bonds broken by these services re-form only after the neutralizer or neutral shampoo.

Permanent wave chemistry: thioglycolate (alkaline, pH about 9-9.5) or glyceryl monothioglycolate (acid, pH about 6.9-7.2) reduces disulfide bonds; the neutralizer (often sodium bromate or hydrogen peroxide) rebuilds them in the new shape.

Hair lightening: melanin is oxidized by hydrogen peroxide plus an alkaline activator; the lift depends on peroxide volume and time, and underlying pigment is exposed in the sequence red, red-orange, orange, orange-yellow, yellow, pale yellow.

Volume mapping for peroxide: 10 volume lifts about 1 level, 20 volume about 2, 30 volume about 3, 40 volume about 4; depositing tone needs low volume, and on-scalp lightening is generally capped at 20 volume.

Relaxers: sodium hydroxide (lye) and guanidine hydroxide (no-lye) straighten by breaking disulfide bonds; a base cream protects the scalp, and the relaxer must be rinsed thoroughly before the neutralizer or normalizing shampoo.

Level system: hair color levels run 1 (black) to 10 (lightest blonde); tone is described separately as warm, neutral, or cool, so a formula names both level and tone.

Texture, porosity, and density are independent: texture is strand diameter, porosity is the cuticle's ability to absorb moisture, density is strands per square inch; each changes processing time or product choice.

Sanitation tiers: clean removes visible soil; sanitize reduces bacteria; disinfect kills most organisms on hard nonporous surfaces; sterilize destroys all microbial life and is reserved for items that penetrate skin.

Skin layers: epidermis (stratum corneum, granulosum, spinosum, basale), dermis (papillary and reticular), and subcutaneous layer; the dermis holds collagen and elastin that determine firmness.

Fitzpatrick types I-VI predict UV response: type I always burns and never tans; type VI is deeply pigmented and rarely burns; higher types need more aggressive exfoliation and carry post-inflammatory hyperpigmentation risk.

Skin analysis order: cleanse, observe under magnification, assess oiliness, pore size, hydration, and sensitivity, then select products; extractions follow softening with warm steam or a keratolytic.

Acid exfoliation strength depends on pH, concentration, and free-acid availability: lower pH means more free acid and more exfoliation; a 30% glycolic at pH 3 is not equivalent to 30% at pH 1.5.

Contraindications for heat and electrical treatments include pregnancy, pacemakers, epilepsy, recent chemical peels, and metal implants; treat these as absolute stop rules rather than judgment calls.

Massage direction on the face follows lymphatic drainage toward the nodes: light pressure, superficial strokes, moving from the center of the face outward and downward to the neck and clavicle.

Extraction rule: only extract pustules and non-inflamed comedones; never squeeze inflamed cysts, and never extract over a cold sore or broken skin.

Sun protection: SPF measures UVB protection only; broad-spectrum labeling adds UVA, and reapplication is needed roughly every two hours because protection degrades with sweat and time.

Nail anatomy: the matrix produces the nail plate, the eponychium is the living cuticle tissue at the base, the hyponychium seals the free edge, and the lunula is the visible portion of the matrix.

The nail plate is about 0.1 mm thick at the free edge and roughly 50 percent harder than skin; it is composed mainly of keratin with low water content and does not absorb water quickly.

Cuticle work: push back only the eponychium gently; cutting living tissue risks infection and is restricted or prohibited in many jurisdictions, so trim only loose dead tissue where rules allow.

Nail growth: fingernails grow about 3.5 mm per month, toenails about 1.6 mm per month; growth slows with age and in cold weather and is faster in summer.

Shaping: square leaves corners at 90 degrees, squoval rounds them, oval and almond taper; file in one direction from corner to center to avoid splitting the free edge.

Disinfection: implements must be washed, then immersed in an EPA-registered hospital disinfectant for the label contact time (often 10 minutes) after every client; files and buffers are porous and generally single-use.

Acrylic application: mix monomer and polymer to a medium consistency, apply in thin layers, and keep product off the skin; liquid-to-powder ratio controls cure speed and strength.

Gel polish removal: file the top coat, saturate a cotton pad with acetone, wrap in foil for 10-15 minutes, then gently push off softened product; scraping hard damages the nail plate.