A waterborne paint needs dry, filtered compressed air at the station, with an air class set from the paint's technical data sheet. It also often needs more flow, because many workshops speed up basecoat drying by blowing air over it. In practice: a refrigerated dryer at the compressor outlet, fine filters at the station, and a compressor sized with the blowers included.
What changes with a waterborne basecoat
A waterborne basecoat dries as the water it contains evaporates. Two consequences for compressed air:
- Atomising and blowing air must not bring water. Water condensed in the hose slows evaporation, leaves marks and can spoil the adhesion of the next coat.
- Drying uses air. Between coats, the workshop often blows air over the basecoat, with stand-mounted or handheld blowers. These devices use air throughout the drying phase.
Oil remains an enemy, as with solvent paint: an oil aerosol leaves craters. Our page on compressors for spray booths recalls the general rules for supplying a booth.
What air quality to aim for?
ISO 8573-1 classifies compressed air on three criteria: particles, water and oil. The class to aim for depends on your paint: its maker usually states it in the technical data sheet or application guide. Our compressors are lubricated; the air class at the station is set with our technicians. Our guide to ISO 8573-1 explains how to read these classes.
To get there, three stages:
- A refrigerated dryer at the compressor outlet, which condenses and removes moisture. It is built into the K series.
- Fine filters at the paint station, fitted from coarsest to finest, after the last cold point in the network. Our article on fine filters details their role.
- If needed, an activated carbon filter for odours, or a desiccant dryer if the network crosses a cold room where water condenses despite the refrigerated dryer.
Flow, blowers included
Take a workshop with one painter working panel after panel: while he sprays one panel, two blowers dry the basecoat on the previous one.
- Paint spray gun: around 350 L/min, as a rough guide, counted at 100 %.
- Two drying blowers, example assumption of 300 L/min each, continuous: 600 L/min.
- Dusting blow gun: 150 L/min counted at 50 %, so 75 L/min.
- Total: 1,025 L/min.
- With a 25 % margin: 1,025 × 1.25 = about 1,280 L/min.
Without the blowers, the same station needs about 530 L/min. A workshop equipped for solvent paint can therefore find itself short when switching to waterborne. Your blowers' real consumption is in their manual: if it is in cfm, our flow and pressure converter turns it into L/min.
Which compressor to choose?
- Painting without blowers or with just one: the K 75. 1.1 m³/min at 8 bar, 420 L receiver, built-in refrigerated dryer and filtration.
- Painting with two blowers or more: the K 110. 1.7 m³/min at 8 bar, 340 L receiver, same air treatment. It covers the 1,280 L/min of the example.
- A workshop keeping its receiver: the S 110, a standalone screw compressor with the same flow, with a refrigerated dryer sized for 11 kW.
Pitfalls specific to waterborne paint
- Water after the dryer. A pipe running along a cold wall or through an unheated area condenses moisture again. Place the filters and a drain point as close to the station as possible. Our article on water in compressed air lists the points to drain.
- Saturated filters. A clogged element filters less well and drops the pressure. Replace it at the scheduled intervals.
- The lubricator. No lubricator on the line feeding the gun and the blowers. Lubricated tools have their own line.
- Blower pressure. Set it to the value in the manual. Too high a pressure wastes air without drying any faster.
State the paint you use and the number of blowers in your quote request: we will check the flow and air treatment with you.
For your trade: Compressor for spray booths.