Painting Application Techniques and Finish Quality
This domain tests correct technique with brush, roller and spray, the order in which surfaces are painted, the site conditions allowed, and how finish quality is verified.
Methods
- Brush: dip one-third of the bristles, work from dry into wet area, lay off in one direction - along the grain on wood, vertically on walls - to keep a wet edge.
- Roller: load evenly, lay paint in a W then spread vertically, back-roll to level, and stop before the film starts to set.
- Spray: hold a conventional gun 200-250 mm away at 90 degrees, overlap passes by about half, keep speed even; airless needs the correct tip and pressure; mask everything, extract the overspray and tack off the surface first.
Sequence and conditions
Ceilings, then walls, then woodwork and doors; top to bottom; one room at a time, finishing at the exit. Primer, putty and sand, undercoat, two finish coats; sand between coats with 180-220 grit, 320 for gloss, and dust off. Apply at roughly 10-35 degrees C, RH below 85 percent, substrate moisture below 12-15 percent, metal above dew point, never in hot direct sun, rain or fog.
Quality checks
Even sheen, no brush marks, sags, holidays, pinholes or embedded dirt; uniform colour from one mixed batch; dry film checked with a gauge; adhesion checked by a cross-cut tape test.
Worked example
Curtains of paint run down a gloss door. Diagnosis: film applied too thick, paint thinned beyond the label, or a cold room kept viscosity low so the film could not hold. Remedy: let it harden fully, sand flat, then recoat in thin coats at the recommended thinning, working top to bottom with a light lay-off.
Traps
Sanding between coats without dusting off; recoating an uncured primer; letting the wet edge break in a large room; spraying without masking adjacent surfaces.