The Difference Between HVLP And Conventional Spray Guns

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Whether you're doing a refinishing job on a simple woodworking project such as a wall-mounted coat rack, or tackling something more complex, such as refinishing your grandfather's antique rolltop desk, you'll need a little knowledge and some basic finishing equipment to get the job done right. There are two basic types of finishing spray guns available on the market. The newer ones are high-volume, low-pressure guns, also known as HVLP, and then there's "Old Faithful," the conventional spray gun. Both of these guns do a good job of putting on finishes, but each has its own design differences that you will have to consider before you decide which you want to buy.

Conventional spray guns operate at a basic, high pressure. They connect to an air compressor and the finish is "blasted" onto your project using this high pressure. Because this high-pressure finely atomizes the spray, in that it produces very fine particles, this gives a very nice smooth application, whether it be a clear shellac, varnish or paint. Despite this excellent end result, conventional spray guns are only about 30% effective. 30% of the finish actually ends up where it's supposed to go, on the wood. The other 70% is released to the atmosphere. This both wastes material and is detrimental to the environment as well.

The high-volume low-pressure spray guns are new to those who like to tackle "do-it-yourself" projects. These guns increase transfer efficiency, which means that much more of the finish medium is actually transferred to the wood instead of wasted. Unfortunately, many of the solvents used today in wood finishing products are detrimental to air quality. Therefore, not only is it industry standard to use the high-volume low-pressure guns, but it is actually mandatory to use a high-pressure low-volume gun, as ordered many local governments and state. With the HVLP system, air is delivered at much higher volume, but with a much lower pressure, so that more finish ends up on the wood instead of in the air.

There are two different types of high-volume low-pressure spray gun systems on the market. The first utilizes pre-existing equipment, because it converts the traditional spray gun system into a high-volume low-pressure system. This is known as a "conversion high-volume low-pressure spray gun." With this system, the spray gun still runs off an air compressor just as a conventional spray gun does, but it uses much lower pressure, about 25 pounds per square inch. It's not as efficient as the newer turbine air system, but it is still much better than a conventional spray gun and is a cost-effective alternative for someone who already owns an air compressor.

The second type of high-volume low-pressure spray gun is the most efficient, and this is suitable for someone who doesn't already own an air compressor. This spray gun operates off of an air turbine instead of air compressor. This delivers an extremely high volume of air at very low pressure, about four to six pounds per square inch. This is more costly than an air compressor, but because it is so much more efficient, it may be worth the investment if you don't already own an air compressor.

Regardless of whether you are using a high-volume low-pressure spray gun or a conventional spray gun, you still must protect yourself by spraying in a well-ventilated area and use proper safety equipment, including a respirator. In addition, many manufacturers now produce several water-based finishes that are not flammable. In addition, because they use water as a base instead of something like lacquer, they are much easier to use and also cause less harm to the environment than do traditional finishes.

by: Megan Cherry

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