CSLB C-33 Painting & DecoratingCoating ApplicationEasy
A painting contractor is applying a clear lacquer finish to custom-built wood cabinetry. A few minutes after application, the contractor notices a milky, hazy, or cloudy appearance forming in the film, which was previously clear. This defect is commonly known as:
- ASagging
- BBlushing
- CCratering
- DOrange peel
Show answer & explanationAnswer & explanation
Correct answer: B. Blushing
The milky or hazy appearance in a clear lacquer film, especially shortly after application, is known as blushing. It occurs when moisture condenses on the wet film due to rapid solvent evaporation causing a temperature drop (evaporative cooling), trapping moisture within the film.
Why the other options are wrong
- A. Sagging is the downward flow of a wet film, resulting in uneven thickness and drips, unrelated to a milky appearance.
- C. Cratering (or pinholing) refers to small, circular depressions in the film, often due to trapped air or contaminants, not a uniform haze.
- D. Orange peel refers to a texture resembling an orange skin, caused by poor flow, not a milky haze.
Blushing (Lacquer)
A defect in clear lacquer films appearing as a milky or hazy cloudiness, caused by moisture condensation on the film due to rapid solvent evaporation and evaporative cooling.
- Common in high humidity or cold conditions.
- Occurs when water gets trapped in the drying film.
- Can sometimes be remedied by applying a 'blush retarder' or very thin coat of lacquer thinner.
Memory trick: Blushing lacquer, hazy and white, too much moisture, not quite right.