Hair Cutting, Colouring and Chemical Services
Cutting
Hair is sectioned and worked from a guide line. Elevation controls shape: 0 degrees gives a blunt one-length line, 45 degrees gives graduation, 90 degrees gives uniform layers, and 180 degrees gives long layers. Cut with the shears' cutting edge, keep tension even, and cross-check sections for balance. Dry cutting and texturising refine the outline.
Colouring
Temporary colour sits on the surface, semi-permanent direct dyes deposit without lifting, demi-permanent is low-ammonia and deposit-only, and permanent colour uses ammonia to open the cuticle and peroxide to develop and oxidise melanin. Developer strengths: 10 vol (3%) deposits, 20 vol (6%) deposits with slight lift, 30 vol (9%) lifts, 40 vol (12%) gives maximum lift. On the colour wheel, blue cancels orange, violet cancels yellow and green cancels red.
Safety and chemistry
Patch test 48 hours before a first application, strand test on the day, wear gloves, ventilate the area, never seal peroxide and bleach in a closed container, and never store mixed colour. Perms and relaxers break and then reform disulphide bonds: reducing agent first, neutraliser second.
Worked example
A client with warm yellow undertones and 20% grey wants a cool ash blonde. Reasoning: the existing pigment is warm, so a straight ash may read green-grey. Use a lower-volume developer on the resistant grey, pre-pigment where needed, and add a violet-based toner to neutralise yellow. Strand test first.
Traps that cost marks
- Confusing developer volume with percentage.
- Applying colour to a scalp with a cut or rash.
- Assuming 40 vol is always better, which risks damage and scalp burn.