A varnish or lacquer spray gun uses around 350 l/min as a guide, for the whole pass. For a finishing station with one gun and a blow gun, a 7.5 kW 4-in-1 screw compressor such as the K 75 provides the flow and the dry air you need. With two spray guns and a sanding station running together, move up to the K 110.
The other uses of air in a woodworking shop are on our page on compressors for joinery workshops. Here we only cover the finishing station.
How much air does a finishing gun use?
Our configurator uses 350 l/min for a paint or varnish spray gun, at about 6.3 bar. That is an order of magnitude: the exact figure depends on the type of gun and the nozzle, and it is in the manufacturer's manual.
- Conventional or HVLP gun: the air atomises all the material. The air flow is the figure that sizes the compressor.
- Air-assisted airless or airmix gun: a pump pressurises the material, and the air only refines the fan. The gun uses less, but if the pump is air-driven, it uses air too: add both.
A finishing gun blows without a break through the pass, panel after panel. So count it at 100 %.
The calculation for a finishing station
Simple station, one spray gun and a blow gun.
- Spray gun: 350 l/min, counted at 100 %.
- Blow gun to dust off the parts: 150 l/min as a guide, counted at half because it works in bursts, so 75 l/min.
- Subtotal: 425 l/min.
- 25 % safety margin: 425 × 1.25 = about 530 l/min.
Finishing shop, two spray guns and a sander.
- Two spray guns: 2 × 350 = 700 l/min.
- Orbital sander for de-nibbing between coats: 350 l/min as a guide, counted at 100 % because it runs for long periods.
- Blow gun: 75 l/min.
- Subtotal: 1,125 l/min.
- 25 % safety margin: 1,125 × 1.25 = about 1,410 l/min.
The first case fits on the K 75, which delivers 1.1 m³/min, or 1,100 l/min at 8 bar. The second needs the K 110, which delivers 1.7 m³/min at 8 bar.
Which compressor for your finishing?
| Use | Recommended model |
|---|---|
| Occasional finishing, a few pieces a week | E 75, 0.9 m³/min piston compressor, followed by a dryer and filter |
| A finishing station used every day | K 75, 4-in-1 screw compressor, 420 L receiver |
| Two spray guns and sanding at the same time | K 110, 4-in-1 screw compressor, 340 L receiver |
A piston compressor works as long as finishing stays occasional: it needs rest time between cycles. A full day of lacquering needs continuous flow, which is what a screw compressor is built for.
The air that keeps defects off the wood
Water and oil aerosols reaching the gun leave craters, white blushing or adhesion faults. Our compressors are lubricated: the treatment after the compressor is what delivers clean air to the gun.
- A refrigerated dryer after the compressor removes the moisture. The 4-in-1 models have it built in. Our article on which air dryer to choose compares the options.
- A fine filter at the finishing station, as close to the gun as possible, catches what forms in the network. The ISO 8573-1 air quality class to aim for is set with our technicians, depending on your product. See our article on fine filters.
- A separate line for finishing. If the shop uses a lubricator for its air tools, it must never sit on the line feeding the spray gun.
Pitfalls at the finishing station
- Pressure at the gun, not at the compressor. Set the pressure with a regulator at the station, trigger pulled. A long or thin hose drops the pressure during the pass and changes the atomisation.
- A cold network. In an unheated workshop, water can condense in the pipes after the dryer. Fit drain points at the bottom of the drops.
- Forgotten draining. A receiver full of water sends moisture back into the network. An automatic drain solves this.
To size your whole workshop, enter your tools in the configurator, or describe your finishing station in a quote request.
For your trade: Compressor for joinery workshops.