Barbering Services, Tools, and Chemical Applications
This domain tests the cutting, shaving, and chemical services a barber performs and the tools and chemistry behind them. Questions commonly ask for the right tool, the right angle, the right product, or the right reason to refuse a service.
Cutting and shaving
- Core tools: shears, clippers, edgers and trimmers, straight razor, guards, and combs. Guard and blade numbers rise with cutting length, so a lower number cuts closer.
- Fades blend from short to long, tapers shorten at the neckline and sideburns, and a line-up defines the hairline and beard edge.
- Straight-razor shaving: hold the razor at about a 30-degree angle, stretch the skin taut, shave with the grain in short strokes, and use a hot towel and lather to soften the beard.
Chemical services
- Relaxers: sodium hydroxide (lye) products run about pH 12 to 13; no-lye versions use calcium hydroxide or guanidine. They break disulfide bonds and straighten. Protect the scalp with base, avoid shampooing for 48 to 72 hours before, and neutralize thoroughly to restore pH.
- Permanent waves: ammonium thioglycolate at about pH 9 to 9.5 reduces bonds; the neutralizer (sodium bromate or hydrogen peroxide) rebuilds them.
- Color: permanent color is oxidative and needs developer. Patch test 24 to 48 hours before, and do a strand test when the hair's history is unknown.
- Retouch appointments typically fall every six to eight weeks; a virgin application is different from a retouch and must not overlap previously processed hair.
Worked example
A client whose hair was relaxed last month wants a perm this week. Decline and reschedule. The hair has already been through one reduction process, and a second so soon risks breakage. Wait at least six to eight weeks, then strand test before perming. Reasoning: both services break and rebuild disulfide bonds, and the cortex needs recovery time between them.
Traps that cost marks
- Skipping the patch test or strand test.
- Overlapping relaxer onto previously relaxed hair.
- Confusing relaxer chemistry (strong alkaline, pH 12 to 13) with perm chemistry (mild alkaline, pH 9 to 9.5).
- Using a dull blade, which pulls and irritates the skin.
- Forgetting that a neutralizer is required after every bond-breaking service.