Learning to Spray with a Cheap Gun

Bought in quantity and treated as disposable, low-end cup guns have their place. But it's hard for a beginner to troubleshoot his results if he's using cheap equipment. March 4, 2009

I've built custom stair railings for the last eight years and have always subbed out my finish. For the last year I've read this forum religiously, quizzed my finisher, and practiced finishing techniques on smaller projects. I've gotten pretty comfortable with prepping, staining, and sealing, but I am still not able to lay down a nice smooth top coat.

I've sprayed mostly Magnalac out of cheap harbor freight guns and no matter how much I thin the material or adjust the gun I always end up with a topcoat that looks like orange peel. Don't get me wrong, I'm aware that my equipment is by far less than ideal, but I've heard experienced finishers on this forum claim to be able to lay a nice finish with cheap guns. I was hoping to get more practice in before purchasing a professional setup, but is it the setup that is limiting my abilities? If so, 99% if my finish will be on site stair railings. What would you recommend for a setup to spray sealers and lacquers on site? Thanks for any input.

Forum Responses
(Finishing Forum)
From contributor J:
I just picked up two cost effective Astro pneumatic HVLP guns on - line from Spraygun world in California. I should have purchased these ten years ago – I love them.

From contributor J:
For onsite finishing I would go water based. We never had good luck with the Astro Pnuematic spray guns. I would say switch to a better product for topcoats and invest in decent spray equipment.

From Paul Snyder, forum technical advisor:
There are a number of possible reasons you are not getting good atomization with your spray gun. The first I would look at is the air pressure to the gun and whether or not your compressor is supplying enough volume (CFM) to run the gun. Too little air pressure or volume can produce a coarse spray pattern leading to orange peel. There's also the possibility that the spray gun is damaged or defective. An experienced sprayer could test the gun pretty quickly and tell you if it's capable of spraying a decent pattern. Then there are all the other possible reasons that can cause orange peel.

There's no reason you should not be able to lay down a flawless finish using the spray gun and finish you have. There are better choices for both, but neither should keep you from achieving the results you want.

If you do decide to go with a better spray gun, first find out how much air, in CFM, your compressor supplies and then find out how much air the spray gun you're considering needs to operate properly. It's not uncommon for a spray gun to need 12 CFM, or more, to spray well. That much air translates to a pretty large compressor. If your compressor doesn't supply enough air for the spray gun, it doesn't matter how good a gun it is, it won't produce consistently good results.

There are a couple easy options for spraying on-site. You can use a portable compressor with a spray gun that only requires a small amount of air or you can go with a turbine unit. There are pros and cons to both choices and that could go into a whole discussion by itself.

From the original questioner:
Thanks for the info everyone. Paul said it best in: "there's also the possibility that the spray gun is damaged or defective. An experienced sprayer could test the gun pretty quickly and tell you if it's capable of spraying a decent pattern."

I'm using a 30 gallon shop compressor so air volume shouldn't be a problem. I've tried more pressure with standard suction guns and less pressure with gravity feed HVLP guns both producing the same results.

From contributor T:
In all honesty it’s kind of a catch 22. If you’re inexperienced to know what to do or look for because you've never gotten the results you see others get or hear they get, then you’re working blind so to say.

Even if you buy the best touted gun on the market, if you don't know how to adjust it and the proper viscosity as well as CFM you need for the gun to work at its best, you might never get what you’re looking for or believe you should be getting. Even the nicest smooth wet coats I apply as they dry (if gloss) will not look perfectly level once dry because of shrinkage. They should look smooth when first applied. Before running out and spending lots of money on a great gun, tell us what you’re using now as to gun and material, your thinning ratio, how much CFM your gun requires, how much your 30 gal compressor has available at the tank pressure you have, and the size of the air tank also.

It may be just a matter of talking you through it - something as simple as a bigger compressor or slowing your spray passes down to lay on a thicker coat than your doing now or adding a very small amount of retarder, or other variables, if you can learn to spray with a cheap gun and get great results then you can spray with any gun and do the same. If you’re in-experienced then the best gun in the world won’t help you. You also need to know how wide your fan is at 8" from the surface which if too small or big could be the problem.

From contributor R:
Can you just ask your finisher what type and brand spray guns he uses on your work? Once you know, you can then ask him/her to show you how to use them. If you’re happy with the end results of your current finishers work you should feel comfortable asking all about the ins and outs of finishing. My guess is that you should have every finishing process mastered in about a week or two.