Finish TradesCâu 220 / 700
An old, sound exterior paint film shows heavy chalking (a powdery residue on the surface). Before repainting, the MOST important prep step is to:
a.Apply the new coat directly so the chalk bonds it tighter
b.Add extra water to the new paint so it soaks into the chalk
c.Wash and remove the chalk residue so the new coat can bond to a sound surface
d.Scuff-sand only, leaving the chalk in place for tooth
Giải thích
Chalk is a loose powder from binder breakdown; a new coat applied over it bonds only to the powder and peels. Washing (and sometimes a bonding primer) removes the chalk so the new paint adheres to sound material. Painting over chalk, thinning to soak in, or leaving chalk as tooth all lead to poor adhesion.
Luyện miễn phí toàn bộ 700 câu hỏi — không cần đăng ký.
Câu hỏi liên quan cùng chủ đề
- A painter must achieve a specified DRY film thickness. During application the coating is checked with a wet-film gauge. Why is the WET film reading higher than the target dry film thickness?
- New portland-cement stucco or fresh concrete is highly alkaline. Applying an ordinary oil-based paint too soon can cause which specific failure?
- Bare galvanized steel is to be painted. Which preparation gives the BEST long-term adhesion?
- Why do finish carpenters and painters often 'back-prime' exterior wood trim and siding before installation?
- A room measures about 12 ft by 15 ft with 8 ft ceilings. Ignoring openings, the four walls total roughly 432 square feet. If one gallon of paint covers about 350 square feet per coat, how much paint is needed for TWO coats (rounded up to whole gallons)?
- Cedar and redwood siding can bleed brownish stains through ordinary paint. Which primer choice BEST prevents this discoloration?
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