NH Cosmetology cheat sheet

Hair shaft layers: cuticle (outer protective scales), cortex (bulk, melanin, disulfide bonds), medulla (central core, may be absent in fine hair).

pH scale 0-14; hair and scalp are acid-mantle territory near pH 4.5-5.5; alkaline products swell and raise the cuticle, acidic products compact it.

Disulfide, salt (ionic), hydrogen, and peptide bonds govern strength and shape; wet hair breaks hydrogen bonds, so wet setting reshapes and drying re-forms them.

Side bonds: disulfide bonds are broken by thio relaxers and reformed by neutralization; hydrogen bonds are broken by water and heat; salt bonds by pH change.

Porosity = cuticle condition: low porosity resists moisture and needs heat/alkaline help; high porosity absorbs fast and loses moisture, so use lower-pH, protein-supporting products.

Elasticity test: wet a strand and stretch; healthy hair stretches about 50 percent of length and returns; poor elasticity signals weak cortex and limits chemical services.

Density is hairs per square inch; texture is the diameter of a single strand (fine, medium, coarse); these are independent variables.

Growth: anagen (active, years), catagen (transition, weeks), telogen (rest, months); average scalp growth is roughly 0.5 inch (1.25 cm) per month.

Melanin types: eumelanin gives brown-black, pheomelanin gives red-yellow; gray hair has reduced melanin and often a coarser, more resistant feel.

Four basic cuts: solid form (0 degrees, no elevation), graduated (stacked elevation), layered (elevation above 90 degrees), and uniform layer (90 degrees all around).

Elevation determines where weight builds: low elevation keeps weight at the perimeter, high elevation removes weight and creates volume at the crown.

Projection and distribution: natural fall follows the head shape; shifted or perpendicular distribution creates length increase and overdirection effects.

Guide types: stationary guide (all sections cut to one fixed guide) versus traveling guide (each section becomes the guide for the next).

Cutting angle relative to the section: blunt or square cuts create a solid line; beveled or slanted fingers create softer, layered ends.

Cross-checking means cutting the same section from a perpendicular direction to verify balance and even weight.

Styling tools: round brush with tension and heat creates bend; flat iron sets a bend by holding the shape until cool; curling iron barrel size controls wave diameter.

Blow-dry direction follows cuticle: downward airflow smooths; upward airflow lifts and roughens the cuticle for volume.

Face shape decisions: add volume where the face is narrow, minimize width where it is wide; balance long faces with width and round faces with height.

Developer volumes and lift: 10 vol (3%) deposits only, 20 vol (6%) lifts 1-2 levels, 30 vol (9%) lifts 2-3, 40 vol (12%) lifts 3-4; higher volume also means more lightening and more damage.

Color wheel: colors opposite each other neutralize; blue cancels orange, violet cancels yellow, green cancels red; use to select toners and correct unwanted warmth.

Level system 1 (black) to 10 (lightest blonde); identify level and underlying pigment before formulating, because lightening exposes warm undertones.

Permanent color: alkaline ammonia (or substitute) opens the cuticle, peroxide developer lifts and deposits, and the color molecule oxidizes into the cortex.

Demipermanent color deposits with low or no lift and fades over 20-30 shampoos; semipermanent is direct dye that coats the cuticle and washes out faster.

Patch test and strand test: patch test for allergic reaction 24-48 hours before; strand test verifies timing, lift, and color result on the client's own hair.

Relaxer strength: thio relaxers (pH about 9-10) for normal hair; hydroxide relaxers (no-lye calcium hydroxide or lye sodium hydroxide, pH 12-14) are stronger and not compatible with thio.

Relaxer process: base scalp, apply to new growth only, smooth without pulling, time by manufacturer, rinse fully, then neutralize with acid-balanced shampoo to rebuild disulfide bonds.

Texture services: permanent wave uses reducing agent (thio or cysteamine) to break disulfide bonds, then neutralizer to re-form them in the new shape; test curl determines processing time.

Overprocessing signs: excessive swelling, mushiness, breakage, scalp irritation; contraindications include recent relaxer, damaged cuticle, and metallic or henna history.

Skin layers: epidermis (outer, avascular), dermis (nerves, vessels, glands, collagen and elastin), subcutaneous (fat, insulation, support).

Skin types: normal, dry (alipidic, lacks oil), oily (sebum-rich, enlarged pores), combination (oily T-zone, dry cheeks), and sensitive (reactive, redness).

Cleansing steps: cleanse, tone (restore pH), exfoliate (mechanical or chemical), massage, mask, moisturize, and protect with SPF.

Fitzpatrick scale I-VI predicts sun response; lower types burn easily and need higher SPF and careful light-based treatment settings.

Exfoliation: alpha hydroxy acids (glycolic, lactic) act on surface; beta hydroxy acid (salicylic) is oil-soluble and suited to oily, acne-prone skin; enzyme peels are gentler.

Extraction and massage: massage movements follow muscle direction, upward and outward; avoid massage over active acne, inflammation, or recent waxing.

Contraindications for facial services include open lesions, cold sores, sunburn, recent chemical peel, and contagious conditions; refer to a physician when uncertain.

Product ingredient functions: humectants draw water (glycerin), emollients soften and seal (oils, esters), occlusives block water loss (petrolatum, silicones).

Nail anatomy: nail plate (keratin), nail bed, matrix (growth area), lunula (visible matrix), cuticle (dead tissue seal), eponychium (living fold), hyponychium (under free edge).

Nail plate is roughly 100 layers of keratin; growth averages about 1/8 inch (3 mm) per month for fingernails, slower for toenails.

Nail shapes: square (strong corners), squoval (rounded square, durable), oval (natural, weakens wide nails), round (short nails), pointed/stiletto (fragile).

Manicure sequence: sanitize hands, shape with file in one direction, soak, push cuticle, trim only hangnails, massage, base coat, polish, top coat.

Do not cut the eponychium or living tissue; cut only loose, dead cuticle, because breaking the seal invites infection.

Disorders: paronychia (bacterial or fungal inflammation of nail fold), onychomycosis (fungal infection of plate), onycholysis (separation of plate from bed), beau's lines (horizontal grooves from trauma or illness).

Nail fungus and bacterial infections are contraindications for service; do not apply product over infected or inflamed tissue; refer to a physician.

Pedicure safety: single-use files and buffers, disinfected implements, and no credo blade or sharp tool on diabetic clients without clearance.

Polish application: thin coats, cap the free edge, and allow drying between layers to prevent bubbling and peeling.

Sanitation reduces pathogens on surfaces to a safe level; disinfection destroys most pathogens on nonporous implements; sterilization destroys all microorganisms including spores.

Implement classes: clean and disinfect all reusable tools after each client; porous items (files, buffers, wooden sticks) are single-use and discarded.

EPA-registered hospital-grade disinfectant with tuberculocidal claim is the benchmark; follow label contact time exactly, typically 10 minutes.

Blood and body fluid spills: wear gloves, absorb with disposable towel, clean with soap and water, disinfect the area, and discard waste in a sealed bag.

Hand washing with soap and warm water for at least 20 seconds is the primary infection control measure; alcohol sanitizer is a supplement, not a replacement.

Electrical safety: unplug before cleaning, keep cords away from water, never immerse electrical tools, and check for frayed cords or damaged plugs.

Chemical safety: read SDS for each product, store in labeled original containers, keep away from heat and flame, and never mix products such as bleach and ammonia.

Ergonomics: adjust chair and client height, keep wrists neutral, and alternate tasks to reduce repetitive strain in cutting and polishing.

Universal precautions treat all blood and body fluids as infectious; gloves, goggles, and proper ventilation are used for chemical services.