Compressors

Many people ask what size compressors do I need for painting?

A lot comes down to how much you are going to use it and what equipment you are going to use with it.

Just about every compressor out there will give you 100 pounds of pressure, but the real question is will it sustain this during use. What we want to be looking for is how many CFM or cubic feet per minute will your compressor be putting out. The last thing we need is to start losing air pressure (because of losing air volume) while painting. This will cause a bad spray pattern, poor atomization and lousy metallic orientation. This will lead to a smaller pattern and lots of orange peel or you will be shooting dry, instead of nice wet coat. You will only notice this after it has affected the paint job.

On the average most compressors put out 4 CFM per horse on the compressor. For example, a 5 horse should put out 20 CFM. However, many manufactures play with these numbers and sizes. So, before you buy one look specifically for the CFM on the tag. When checking the tag, it may show 8.4CFM at 40lbs but only 5.4CFM at 90lbs so be aware of these ratings. If you need to, you can add an extra tank for more reserve capacity. However, when you run low and the compressor kicks on, this will not help the compressor keep up. Your compressor will still need to keep up on it’s own, when the tanks run dry.

Next, different spray guns use different amounts of CFM, even from the same company. Here is a sample of spray gun pressures and CFM:

TYPE                                  PRESSURE      CFM     

HVLP                                    29LBS           14.4 to 15.2

CONVENTIONAL                 43LBS              13.3

LVLP                                     16LBS               8.8

SUCTION FEED                   50LBS            11 to 12

D.A. Sander                          90LBS             11 to 13

When you choose a compressor, I recommend that you take the largest air user in your toolbox (air tools or paint gun) and add 25% to cover air leakage, pressure drop in hoses, etc.

Hint: You never kick yourself for buying a better compressor, but you will remind yourself everyday if you buy one too small.

If you already have a small compressor, you can still paint. You just have to be very careful about losing air pressure during painting. You just need to paint smaller items or paint larger items in pieces. You would just have to wait for the compressor to catch up. Or you can spray with a LVLP gun. However, a LVLP gun means low volume-low pressure. This means that you will have to paint slower because the gun puts out less material than larger guns and you normally don’t get the paint atomization that you do in a larger volume gun.

Make sure that you drain your compressor at least every week, more in the summer when the humidity is high.