Which factor directly affects the fineness of the paint droplets produced by a spray gun?

• A. Air pressure
• B. Paint color
• C. Surface temperature
• D. Humidity

Answer: (A)

Atomization, the process that creates spray droplets, is driven by the compressed air forcing the paint through the nozzle. Higher air pressure increases the energy available to shear the paint into smaller droplets, giving a finer spray. If the air pressure is too low, droplets stay larger and the finish can look chunky or uneven. Paint color isn’t involved in how small the droplets are—it's a pigment/chemistry property, not the atomization mechanism. Surface temperature and humidity mainly affect drying and how the coating behaves on the surface, not the size of the droplets produced in the nozzle. So, the direct factor controlling fineness is air pressure.