C33 Identifying and Remedying Paint Failures and Defects 5 — Questions and Answers
Question 1: What causes 'picture framing' when rolling paint onto a wall?
- Using a roller with too thick a nap
- Failure to back-roll or blend the brushed edges while the paint is still wet (Correct answer)
- Applying paint in direct sunlight
- Using paint that is too thin
Correct answer: Failure to back-roll or blend the brushed edges while the paint is still wet
Picture framing occurs when brush-cut edges dry before being blended with the roller, leaving a visible border around the painted area.
Question 2: A contractor notices that an oil-based paint applied to a metal door has developed a network of fine cracks resembling crazing glass. What is the most likely cause?
- The metal expanded and contracted before the paint cured
- The topcoat was applied too thick and dried faster on the surface than below (Correct answer)
- The surface was not degreased before painting
- The paint was applied at temperatures below 50°F
Correct answer: The topcoat was applied too thick and dried faster on the surface than below
When a heavy coat skins over rapidly on the outside while the interior is still wet, differential shrinkage creates a crazing or cracking pattern.
Question 3: Which type of stain is most likely responsible for yellowish-brown water marks that bleed through multiple coats of white interior paint?
- Efflorescence
- Tannin bleed from wood knots
- Water-soluble extractives wicking from a water-damaged substrate (Correct answer)
- Mildew
Correct answer: Water-soluble extractives wicking from a water-damaged substrate
Water damage can activate soluble extractives in drywall paper, wood, or plaster that wick to the surface and bleed through standard paint.
Question 4: What is the primary reason paint applied in direct, hot afternoon sun on an exterior surface is prone to failure?
- UV radiation immediately degrades the binder
- The surface is too hot, causing the solvent to flash off before proper film formation (Correct answer)
- High sun exposure causes the paint to absorb excess moisture
- Sunlight changes the color of the pigment before drying
Correct answer: The surface is too hot, causing the solvent to flash off before proper film formation
When a surface is very hot, solvents or water evaporate too quickly, preventing the paint molecules from properly coalescing into a continuous film.
Question 5: A C-33 contractor is asked to repaint a surface showing heavy chalk. Before repainting, what is the proper remediation step?
- Apply a coat of alkyd primer immediately to lock in the chalk
- Pressure wash or scrub off all chalk residue and allow to dry before priming (Correct answer)
- Lightly sand the chalk and apply a water-based topcoat directly
- Apply a bonding additive mixed into the topcoat and paint over the chalk
Correct answer: Pressure wash or scrub off all chalk residue and allow to dry before priming
Chalk must be removed because it acts as a release layer; painting over it results in poor adhesion and eventual peeling of the new coat.
Question 6: Which paint defect is characterized by small, dome-shaped bumps on the paint film caused by trapped moisture or solvent vapor?
- Blistering (Correct answer)
- Pinholing
- Crawling
- Ropiness
Correct answer: Blistering
Blistering forms when moisture or solvent vapor pressure beneath the paint film pushes the film outward, creating bubbles or domes.
Question 7: On a repaint project, the new exterior paint is showing 'lap marks' or 'holidays' where roller passes overlap. What is the most effective preventive measure?
- Apply paint in thinner coats with a smaller roller
- Maintain a wet edge by working in manageable sections and blending overlaps before the paint dries (Correct answer)
- Use a faster-drying paint to lock in each pass quickly
- Apply a mist coat of water before each roller pass
Correct answer: Maintain a wet edge by working in manageable sections and blending overlaps before the paint dries
Lap marks appear when a dried edge is painted over; maintaining a wet edge by working section by section and overlapping into wet paint eliminates visible lines.
C33 Identifying and Remedying Paint Failures and Defects 5
What causes 'picture framing' when rolling paint onto a wall?