Question 1

What is transfer efficiency in spray painting?

Accepted Answer

Transfer efficiency is the percentage of sprayed paint that actually reaches and adheres to the surface. An airless sprayer has 68% efficiency — meaning 32% of the paint is lost to overspray, bounce-back, and atomisation. An HVLP (High Volume Low Pressure) sprayer has 78% efficiency due to its finer spray pattern and lower pressure. This is why spraying requires more paint than brushing or rolling, which are close to 100% efficient.

Question 2

Should I use an airless or HVLP sprayer?

Accepted Answer

Airless sprayers are faster and better for large surfaces like exterior walls, fences, and ceilings — they move more material per minute. HVLP sprayers are better for fine finish work like furniture, cabinets, and trim — they produce a finer atomised spray with less overspray. HVLP requires thinner paint consistency and slower application speed. For most DIY projects, an airless sprayer is more versatile. HVLP gives a higher quality finish where appearance matters most.

Question 3

How many aerosol cans do I need?

Accepted Answer

This calculator estimates 1 aerosol can per 2.5 m² of surface area, based on a standard 400g aerosol can at typical application rates. Can counts are rounded up to whole cans — you always have a small buffer. Aerosol is practical for surfaces under 10–15 m². For larger areas, switching to an airless or HVLP sprayer is more economical and produces a more consistent finish. Aerosol is best for spot repairs, small furniture, and craft projects.

Question 4

What waste factor should I use for spray painting?

Accepted Answer

A 15% waste factor is a good baseline for spray painting — higher than the 10% typical for brush/roller painting because spray creates inherent overspray even at maximum efficiency. For textured surfaces or windy outdoor conditions, use 20–25%. For precise controlled environments (spray booth), 10–15% is sufficient. The transfer efficiency adjustment already accounts for the physics of how spray works; the waste factor is for additional real-world variables like material change and overspray beyond what transfer efficiency captures.

Question 5

What is high-build paint?

Accepted Answer

High-build paint is formulated with a thicker, higher-solids body that fills minor surface imperfections and creates a thicker film per coat. It has a lower coverage rate (7 m²/L instead of 10 m²/L) because it's applied in a thicker layer. High-build is common for exterior masonry, industrial coatings, and surfaces with minor blemishes you want to minimise without filling and sanding. It's not for fine finish work where a thin, even film is required.

Question 6

Why does spraying use more paint than brush or roller?

Accepted Answer

Spray painting atomises paint into fine droplets under pressure. While this produces a smooth, even finish, a significant fraction of those droplets never reach the target surface — they drift in air currents (overspray) or bounce back off the surface (bounce-back). Brush and roller painting apply paint directly in contact with the surface, with near 100% transfer efficiency. This is why spray projects require 22–32% more paint than the theoretical coverage would suggest, depending on sprayer type.

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