CPC30620 Painting cheat sheet

Work health and safety duty hierarchy: eliminate the hazard, then substitute, engineer (guards, ventilation), administrate (procedures, signage), and use PPE last; PPE never replaces a higher-order control.

Australian Standard AS/NZS 1680.1 illuminance targets for interior work: general task lighting around 160 lux, detailed finishing and colour matching around 240–320 lux, with higher values for fine inspection.

Ventilation rule of thumb: spray painting requires mechanical extraction; a minimum face velocity of about 0.5 m/s across an open booth face is the common design benchmark, and solvent vapours are heavier than air so extract low.

Surface preparation grades for timber: sand with the grain, finish at 180–240 grit before priming; moisture content of timber should be 12–15% before coating, measured with a moisture meter.

Masonry and concrete pH: fresh concrete or render is alkaline; coatings generally require the substrate to cure to below about pH 9 and moisture below roughly 12–15% before painting.

Galvanised steel requires a specific etch or primer because the zinc surface rejects conventional coatings; a two-pack epoxy or etch primer is the standard choice, and weathering for several months improves adhesion.

Gloss and sheen selection rule: higher sheen = better washability and harder film; lower sheen hides substrate imperfections; kitchens, bathrooms and wet areas take at least a low-sheen or semi-gloss acrylic.

Lead paint in pre-1970s housing: assume lead is present, do not dry-sand, use wet methods or chemical strippers with HEPA extraction, and follow state/territory lead-removal regulations.

Estimating coverage: paint spreading rate is quoted in square metres per litre; divide total paintable area by the spread rate, then multiply by the number of coats, and add 5–10% for loss and touch-up.

Wet film thickness = dry film thickness ÷ volume solids fraction; if a product is 50% solids and 100 micrometres dry is specified, apply 200 micrometres wet.

Decorative finishes: ragging, sponging and bagging are applied over a fully cured basecoat; the finish coat must be compatible with the glaze, and test panels are made on site before full application.

Wallpaper hanging rule: walls are sized and sealed before paste; paste is applied to the paper for most papers and to the wall only for specific paste-the-wall products; book the paper and check pattern match before cutting.

Spray equipment: airless sprayers use tip size in thousandths of an inch (e.g. 517 = 0.017 inch orifice, 17-inch fan); pressure is adjusted until the fan pattern is even with no tails or fingers.

HVLP spraying operates at lower pressure than conventional air spray, giving higher transfer efficiency (commonly 65–85%) and less overspray; fluid and air are adjusted separately on a pressure-pot or gravity gun.

Two-pack (2K) epoxy and polyurethane products have a pot life after mixing; once mixed they must be used within the stated pot life, and equipment is cleaned before the mixture gels.

Signwriting and graphics: lettering enamels and vinyl films require a clean, dry, dust-free substrate; vinyl application needs a minimum surface temperature (commonly above 10 °C) and squeegee application to avoid bubbles.

Texture and render coating: applied with trowel, roller or hopper gun; coat thickness and drying time between passes are the main controls on cracking, and movement joints must remain uncoated.

Colour matching: tinting is done in small increments; darker colours have lower hiding power, so a tinted primer close to the finish colour reduces the number of topcoats required.

Protective coatings selection: epoxy resists water and chemicals but chalks under UV; polyurethane resists UV and abrasion; a common system is epoxy primer plus polyurethane topcoat.

Defect diagnosis: blistering usually indicates moisture or solvent entrapment; wrinkling indicates recoating before the previous coat is fully cured or an incompatible thinner; sagging indicates over-thinning or excessive film build.

Equipment maintenance: airless tips, filters and hoses are flushed with the appropriate solvent after each use, and spray guns are stored with the fluid needle unseated to protect the seat.