How to Set Up a Spray Gun

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3 Responses to “How to Set Up a Spray Gun”

1. Jay January 8th, 2021

   I disagree. For a gravity feed HVLP gun with a 1.4 tip, I know that I'll need 45 PSI. I use a different gun for each material depending on the cleaning agent. Shellac gets DNA, lacquer and real poly gets MS or lacquer thinner, and the so-called water based polyurethane, which is really acrylic, gets water. I never use the same gun that sprayed any colored material for spraying any type of varnish. You can't clean your gun out 100%, so it will change with time. If you are sprayed water-based finish, you need to disassemble the gun more because the pin will rust. You can't just blow it out. Your spraying goal is to mist the surface. That's especially important if your surface is vertical. Drips are not desired. On horizontal surfaces, you don't want puddles. Before spraying anything, I connect the gun to air pressure and spray it empty in case there is any leftover solvent in it. Then I disconnect it. I support the gun between 2 gallon paint cans. I pour in the amount of the product, thinned appropriately as needed. I had previously drawn a line through the diameter of the material volume screw with a Sharpie. If I needed to disassemble the gun, I wind in the screw all the way, then back out one full revolution. With the gun tip being held over the can, I pull the trigger and wait and watch for the material to drip out. About 1 drop/ second is about right. Next, I lie the lid on the can. I attach the dessicant filter to the gun. Next, I attach the air hose to that. I wipe off the tip of the gun. I fire once in the air. Unless I'm outside, I always wear a respirator. The air volume screw near the bottom of the gun should be in the middle of its range. I begin spraying, adjusting the spray pattern and material volume screw as needed. After spraying, I return any unused material to its can. If it is polyurethane or an oil-based paint, I spray in argon (Bloxygen) per instructions, and rapidly reseal the can. Water-based products and lacquer don't need argon because the dry by evaporation or catalysts and not by oxygen-linking. In general, I use more solvents in gun cleaning than finish material. Paint thinner doesn't work very well, but it's cheap (relatively). The used solvent goes into a waste bucket except for water and DNA, which can go down the drain. Since the cost of water is near zero, I use a lot of it when cleaning the gun (after spraying water-based materials only). Standing over my utility sink while the solvents flow out can be tiresome, so when using water, I place a rubber band across the gun trigger and let the water drain out while the gun is standing up in the corner of the sink. I continue to wear the respirator when cleaning with lacquer thinner or MS. After the gun is cleaned, I recheck my work piece for any drips. Depending on the material, I'll use a clean edge of Bounty or a fine paint brush to spread out any drips. Drying times and curing times are different. Polyurethane is the very best finish, but it takes 21 days to cure. Lacquer dries the fastest, but it is very toxic, it requires a near-perfect spraying temperature and it crazes, which makes it a terrible choice for table tops. Brushed on Deft never seems to cure. Shellac is relatively non-toxic, but it and the acrylics are permanently damaged by alcohol products. There is no ideal choice for finishing materials. No matter what I build, it is the final finishing results that determine its quality.

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2. Steve September 24th, 2016

   What is the tip size you are using lacquer/varnish? I have that same gun but I either get a dull application or when I go slow and look for a shinny application it is heavy and most of the time runs. I haven't tried this air setting approach, I will try that this weekend. I just set it in the green zone I think that is 60/65 lbs.

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3. Alvaro April 2nd, 2015

   unfortunately, the video stops at the point where the pressure is just right, but no indication on how to adjust the material feed.

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