CSLB C-33 Painting & DecoratingCoating ApplicationMedium
A contractor is tasked with painting a large commercial building exterior using an airless spray system. The paint manufacturer specifies a tip size of 515 and a minimum pressure of 2000 PSI for optimal atomization. The contractor observes excessive overspray and a 'tailed' spray pattern, even after adjusting the pressure to 2200 PSI. What is the most likely cause of this issue?
- AThe paint is too thin, causing it to atomize too easily at the current pressure.
- BThe paint hose diameter is too small, restricting flow and causing pressure fluctuations.
- CThe airless pump is undersized for the tip and pressure requirements.
- DThe spray tip is worn, allowing too much paint through at the given pressure.
Show answer & explanationAnswer & explanation
Correct answer: D. The spray tip is worn, allowing too much paint through at the given pressure.
A 'tailed' spray pattern (streaks at the edges) and excessive overspray, despite adequate pressure, are classic indicators of a worn spray tip. As a tip wears, its orifice enlarges, allowing more paint to pass through and failing to produce a sharp, consistent fan pattern.
Why the other options are wrong
- A. If the paint were too thin, it would likely cause dripping or runs, not typically a tailed pattern at appropriate pressure.
- B. An undersized hose might cause pressure drop at the gun, leading to poor atomization and a heavy, wet pattern, not necessarily a tailed one with overspray.
- C. An undersized pump would struggle to reach or maintain the required pressure, leading to poor atomization and spitting, not necessarily a tailed pattern with good atomization at the center.
Airless Spray Tip Wear
Airless spray tips wear out over time due to the abrasive nature of paint, leading to an enlarged orifice and a wider, less defined spray pattern, often with 'tails' and increased overspray.
- A worn tip increases paint consumption.
- It reduces transfer efficiency.
- It produces a poor finish quality (tailed pattern, uneven coverage).
Memory trick: If your spray is stray, look at the tip today.