Elective Units of Competency: Specialist Finishes, Spray and Decorative Work
What the electives add
Elective units let a painter specialise - spray application, decorative and textured finishes, wallpaper, protective coatings, or estimating and supervising. Questions in this domain test the technical reasoning behind a chosen method, and they reward candidates who can link product data to site conditions.
Concepts to master
- Spray application: conventional, airless and HVLP equipment; tip/orifice selection; atomisation; overlap; pot life; and the relationship between viscosity, pressure and finish quality. Understand overspray control, masking, and static or ignition risks.
- Decorative and textured finishes: base coats, trowel or roller techniques, sample panels, and the importance of a client-approved mock-up before full application.
- Wallcoverings: surface sizing, paste selection, matching patterns, and booking for accurate joins.
- Protective coatings: DFT (dry film thickness) versus WFT (wet film thickness), coverage rates, stripe coats, recoat windows, and environmental limits on temperature and humidity.
- Estimating: linear and area measurement, deductions for openings, allowances for waste and coats.
Traps in questions
Common distractors swap WFT and DFT, ignore the recoat window, or suggest applying a coating outside the manufacturer's temperature range. Another trap is choosing a decorative method without a sample panel approval.
Worked example
A specification requires 75 µm DFT and the product has 60% volume solids. WFT = DFT ÷ volume solids = 75 ÷ 0.60 = 125 µm wet. If a question offers 45 µm, that answer has inverted the formula.
Rule of thumb
Always read the product data sheet before choosing a method: it dictates film build, recoat time, thinning and environmental limits. When a question conflicts with the data sheet, the data sheet wins.