Spray System Options - created 07-09-2007

Jackson, Brady - 07/09/2007.12:08:09

There are so many options for a spray finishing system, and I have little knowledge of what different operations require. I would like to purchase a sprayer that can deliver a fine finish using nitrocellulose lacquer and shellac. I have heard good and bad things about HVLP sprayers, what are the drawbacks of one of these systems? Am I better off getting a compressor and some sort of gun?

I'm very new to spray finishes, as all my previous finishes have been French Polish. The library seems to be missing some basic information on the different spray setups, and I would appreciate some advice from experienced sprayers.

Brady you just missed a pretty comprehensive discussion of HVLP in the last month. Basically HVLP is divided into two formats, Turbine systems like Accuspray and Fuji and the conversion cap systems that use conventional air compressors but drop the pressure inside the air cap. There are also conventional guns that meet HVLP standards, i.e. at least 65% of the material ends up on the surface. There are too many variables to say that one system is better than another or that one brand is best. I think most folks who have used a gravity feed gun will agree that it's easier to clean and doesn't waste as much.

Spraying thicker materials at colder temperatures is a reality for many of us and that raises a whole host of other issues.

Oil bath compressors have a bad habit of introducing oil into your air stream. Good filtration is a must.

Turbine compressors heat the air going through which can be good or bad.

Conversion cap HVLP guns use a lot of air (15-22 cfm) so might require a larger compressor than a conventional gun.

A question you could ask yourself is whether you might start spraying polyester in a few years, if so you'll need a larger tip, say 1.4 -2.0 mm range.

So is an HVLP rig good for spraying lacquer? I am willing to shell out for the best rig I can, but I dont want to spend a whole lot of money on a sprayer that won't give me a fine lacquer finish. Frankly, the myriad of options are somewhat mindboggling.

I always recommend a conventional air compressor and an HVLP conversion gun. This will deliver a slightly better atomized finish than a turbine setup, and you get the huge benefit of having an air compressor in your shop that can do all kinds of stuff.

Are there any gun designs in particular that are better than others for use with a compressor? Are all HVLP conversion guns pretty much the same design? (If you can't tell, I really know nothing about spraying :)

Brady, I recommend a Badger 400 sprayer you can google dixie art. Its basically a touch up gun that has more than enough capacity for a guitar, yet it is not so big and heavy as regular guns. It did a fine job with water-based spray lacquer on my uke.

Hi Brady,

For the not so fine - "as is" lacquer finish the better quality guns are worth the additional money. For spraying cars and cabinetry where buffing the finish out is not practical the better equipment delivers a superior finished product.

I'm not certain if I've seen a difference in atomization from conversion guns versus dedicated turbine guns, but I agree that if you don't have a shop compressor already, it's probably a good idea to go that route. That said, I'm back to spraying with my turbine gun in summer for the better blush prevention (heated air stream helps).

Personally, I would look at gravity feed guns. Since the paint is going to come out the fluid tip as soon as you pull the trigger, all the air that is being delivered to the air cap is used to atomize the paint. With a suction feed (the one with the pot under the spray head) you need a certain amount of air to create a vacuum at the air cap to pull the paint up out of the pot, then it is atomized.

With this set up you can usually get away with a smaller compressor if this is a consideration.

In the automotive trade we have switched to gravity feed for nearly 20 years. While it's possible to purchase good suction feed guns, the really outstanding spray guns are all gravity feed.

As for HVLP, as stated before, there are turbine systems and conventional spray guns that are HVLP. I've use countless models from both sides of the camp. Turbines aren't really suitable for a small home set up in my opinion. The are very loud. Only good for spraying. You don't have a compressor for other uses, and if you live somewhere that it is hot, then the heated air that the turbine creates is going to give you all kinds of grief trying to get a great finish. However, I use to live in Canada and it was the greatest thing going when we were spraying during the winter.

I also wouldn't get to concerned about trying to find the prefect HVLP gravity feed gun. The gains that you get from the efficiency of these guns are only really realized by very competent painters that are spraying large volumes of paint daily. Poor spray technique will very quickly wipe out any savings in material. That's not to say not to buy one. Just don't let it make or break your buying decision.

I friend who is an auto paint instructor for 20+ years recommended me a HVLP jam gun that is sold by Harbor Freight. He says that it's low cost is a bargain, and that you'd need to purchase a gun 8x the price before you'll see a notable difference in quality. Because of this, he recommends this gun to his students and also stocks it in his intro classes

Google for Harbor Freight, and then check out item 90977-0VGA. At 29psi and 5.91cfm, it doesn't take much of a compressor to keep this supplied with air. Two weeks ago this was on sale at a significant discount, so I picked up two (one dedicated only for clear and one for colors) for less than one sells for today.

My experience with HVLP turbine guns is 180 degrees out from Allen's - I spray in all kinds of temps and humidity situations and get a great result - to the point where area repair shops are asking me to handle nitro touchup work. The primary reason why I would not consider sending a guitar out for finishing is that I get a better result at home.

Turbines are a bit different that conventional guns, but a little practice takes care of the differences for most purposes. At to the issue of small home set-up, many of us end up spraying outside and dealing with wind, etc. The ability to spray anywhere (side yard; over at a rural buddy's place, etc.) should not be underestimated if you do not have a dedicated spray booth.

Also, the issue of compressor size should be noted - most conversion guns require 4-6 SCFM at 40 PSI, which is borderline for anything smaller than stationary systems, so if you go that route, figure on a 60 gallon, 5 hp system to be able to reliably use full sized HVLP guns.

FWIW, I've got both styles of systems, and usually end up using a Turbinaire 1235 HVLP for most jobs, and a Awata or Sharp for minor touchup work.

That compressor estimate sounds pretty high to me. I sprayed for a couple years using a hardware-store HVLP gun fed by a 2HP pancake compressor.

You don't need a big compressor to spray a guitar. You generally only use 10 to 20 seconds worth of 4-6 SCFM at a time. But if your buddy wants you to spray his car then you will need something bigger.

I've run a touch-up gun or mini-HVLP off a pancake, but IMO it's a little wimpy for spraying unthinned McFadden's from a full-sized gun. I agree that if you are not spraying aircraft or cars (can we say Imron? Never again...), you can get by with a smaller tank. I don't think I'd go smaller than 2 hp/6 gallon, and with those compressors running 75% of a Borg-brand 60 gallon, why not get a tool that will run a ROS or air drill?