Selecting a spray system

If you want a quick summary of how I would choose a spray outfit, keep reading. But for a better understanding of the different spray systems, see the separate page on spraying finish and other application techniques.

Okay, I have a bunch of spray options that I own and have used, so here is my evaluation, loaded with personal bias.

Conversion Guns

The low cost solution (around $100) that works well (if you have a compressor), that I often recommend, is the Porter Cable PSH1 gravity feed HVLP (High Volume Low Pressure) conversion gun, or equivalent. It is called a conversion gun since it runs off a high pressure compressor, rather than a low pressure turbine. Not shown in the picture is the pressure reducer/control that comes with the gun and attaches to the bottom, where the air enters. I can leave my compressor at the usual 100 psi or so, and reduce it to 30-40 psi where it enters the gun, then the gun reduces it to about 5 psi at the tip.

This gun runs off my cheap compressor that produces about 4 cfm (half the volume required by the gun) but has a 13 gallon tank. That means that I can use air from the tank when the gun "uses" more air than the compressor produces, and when I pause, the compressor will continue to run to replace the air in the tank. Overall the tank allows me to keep the spray trigger pulled an average of half the time (since I am using air twice as fast as the compressor produces it). This is not a problem - with typical spraying it takes me 5 minutes or more to get ahead of the 13 gallon tank (but I have to stop several times per minute with my small compressor with the 1 gallon tank). A larger tank would allow me to spray longer before I had to stop to allow the compressor to catch up... average over a longer period, but the large tank requires a lot of time to fill up before it is ready to use.

PSH1 or equivalent? Harbor Freight sometimes has a very similar gun for as little as $25 (but you purchase the pressure reducer separately). The holes in the air-cap/nozzle are not quite as precise as in the name brand gun, and the atomization isn't quite as good, but it works "okay." Other vendors offer copies that are more or less like the Porter Cable gun.

Initially the HVLP "conversion" guns were considered a compromise, but the technology has advanced so that they include the best guns - if you have a good compressor, a turbine is no longer required. The newest guns recognize you may be using a smaller "contractor, hot-dog" compressor, so there is a whole lineup of "LVLP" (Low Volume Low Pressure) guns that use about half as much air as most of the HVLP guns.

Many of the best guns on the market are now conversion guns, presumably better than the Porter Cable PSH-1. I believe the experts who say better guns are available, but I have not used them. I suggest you call the folks at Spray Gun World - they are knowledgeable, and sell so many different brands that they appear to have less bias towards a single vendor.

Turbine guns

I also have a Turbinaire 3 stage turbine, pressure cup HVLP gun, variable speed, chosen because somebody owed me money and offered this. It originally cost about $700, and has worked very well for quite a few years. However, to my dismay, Turbinaire only sells through dealers, and most of the dealers are "closing out" so I cannot get the repair parts I need. The factory admits they no longer stock the parts for their "obsolete" models, so the simple answer, I wouldn't touch the Turbinaire brand, and have had to trash the gun because I couldn't buy a $50 replacement spray tip. I bought a replacement gun, made by C.A.Technologies, from Spray Gun World, a most helpful company, with wide variety of products for all types of use and budgets, and great prices. In fact the CA Technologies gun was so good, and inexpensive, that I bought a second unit so I could use sealer in one and finish in the other, or similar combinations.

I had a cheap single stage turbine system, but sold it. If your material is perfect, the atomization (making of a mist of paint) is fine, but it isn't very forgiving. Since you have minimal air volume, and many of the critical gun parts are plastic, I have heard these systems described as for "single project" use, where the quality decreases as the material wears the plastic parts. I kept the Porter Cable gun, and the Turbinaire, and sold this one.

If I were buying another turbine system, I would be sure to get at least a 3 stage or preferably a 4 stage turbine. Some of the turbine units are notoriously noisy, others are quieter. Most turbine guns have a pressure cup (below the gun) but if the choice were available, I would try to find a good gravity feed gun. I would also look for stainless steel needles and nozzles and parts that touch the fluid, especially if you use any water based finishes. My current turbine has variable speed, but you can use a garden hose valve if you want to reduce the air volume. I do not have a particular turbine brand that I can recommend.

Most of the time I use the turbine gun (with the material cup at the bottom), either because I am spraying a larger item and don't want to wear out my cheap compressor, or because I can turn the volume down for detail work. When I am doing larger items, it is easy to keep the paint cup at least half full, so there is little concern about tipping the gun, but when the amount of paint in the cup gets low, the gun gets really cranky about what position it is held in. It also has a longer material path (the tube that goes to the bottom of the cup) so it is hard to use the last bit of the material, and takes slightly longer to clean.

Generally I prefer a gravity cup, such as on my Porter Cable conversion gun. The shape of the bottom of the gravity cup allows me to tip the gun into almost any position, and with the short material path, I can use the last tiny bit of material (important if you have some tinted finish you want to use up without mixing extra just to "prime the gun"). The short path also makes cleanup slightly easier - not an issue with most water-base finishes, but makes me choose the gravity feed gun if I am facing a tough cleanup.

Airless sprayer

I have an airless sprayer that I use for latex paint, but it does not atomize paint as well as an HVLP sprayer. When I was buying it, the salesman immediately stopped trying to sell me one, when I mentioned furniture.

Non-HVLP (conventional) spray systems

I have, and no longer use, a conventional gun with a large paint pot, a conventional gun with suction cup, and a conventional touch up gun. Why don't I use the non-HVLP guns? WAAAAY too much lost material. This old technology uses a relatively high air pressure to get fine atomization of the paint, but that makes the paint move so fast that much of it bounces (or never reaches the target) and becomes overspray. I estimate that I use twice as much material to spray an item with a conventional gun as it takes to spray the same item with an HVLP gun, and the better HVLP gun gives finer atomization leading to finer finish. Reducing the volume of air on my turbine gun allows me to hit as small an area as the conventional touch-up gun, so I don't even use that one.

Turbine vs. Compressor

The first conventional spray guns required a compressor. When HVLP was "invented" it assumed a turbine with a high volume of relatively low pressure air. Later the conversion guns were invented, to allow HVLP performance with existing compressors. The first conversion guns were a poor compromise, but have improved, until now some experts argue that the best conversion guns are now better than the turbine guns.

A turbine has a few advantages: The air delivered to the gun is warm and relatively dry. Some prefer not to spray with warm air, but I prefer it to cold, which can cool the work, slow the curing, and even condense moisture in the finish (blushing). The turbines are far more portable than a large compressor. They require less power - any I know plug into a household outlet. And you don't have to wait for the air tank to fill before using a turbine.

A compressor has it's own advantages: The air delivered to the gun is cool, (since it expands as it leaves the tank), but the cooling can lead to moisture problems in the tanks, air lines, and guns. The small high pressure air hose is more convenient than the far larger hose used on a turbine. There are many uses for compressed air in the shop, which justifies a better compressor and larger tank. Portable compressors are heavy, especially with "good size" tanks. A properly sized compressor may be 5 hp or more, which will require a special electrical circuit; a smaller compressor will not support continuous spraying.

Nozzle/cap

One other factor nobody discusses. Many guns (including the Porter Cable) have about 8-10 tiny holes for air to come out around the primary nozzle. This is presumably to improve the quality of the atomization (although my turbine guns do not have the small holes, and work great). I spray outdoors, so a gust of wind can blow material back into the gun and plug those holes. They are a pain to clean (the holes are too small for most cleaning weapons). To me, a new gun gets extra points if it does a good job without those tiny holes, but experts tell me the little holes really improve the spray quality. Recently I have been leaving the aircap in a jar of denatured alcohol between uses - the alcohol keeps water base finishes from curing, which presumably will help keep the holes clear.

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