You may not realize it but Apollo Sprayers, the sponsor of this website, is more responsible for HVLP becoming today’s dominant spray technology than any other spray-gun manufacturer. This is not to say that it wouldn’t have happened anyway, but Apollo did get it started.
Spraying technology has been around for over 100 years. It has been based on high-pressure air produced by a compressor. The air is stored in a tank and fed to the spray gun through a hose. The high-pressure air then turns a stream of liquid exiting the spray gun into a fine mist and propels it toward the workpiece.
This is a great technology, but it has the disadvantage of creating a lot of bounce back—the mist under high pressure bouncing back off the surface only to be exhausted into the atmosphere. The result is a lot of wasted finish.
The wasted finish was never an issue, but the exhaust became one during the 1970s when society turned its attention to cleaning up the environment. The exhausted solvents participate in creating air pollution.
The area of the country most concerned with air pollution was, and is, the Los Angeles basin. A government entity comprised of five counties was set up to try to reduce this pollution. Its name is South Coast Air Quality Management District, or SCAQMD.
An Alternative Technology
There existed an alternative technology to compressed air. It dates back at least to the 1930s and the Kirby vacuum cleaner, which came with a little spray gun in its accessory kit. This gun attached to the vacuum cleaner's air outlet and could be used to spray very thin liquids, primarily soapy water for cleaning carpets and fabrics.
A French company, Volumaire, was probably the first to adopt this technology in the early 1960s to produce a stand-alone spray gun not attached to a vacuum cleaner. It was very low-powered and consisted of a small, box-mounted vacuum motor, a hose and a crudely designed metal spray gun.
In 1966, Apollo Sprayers, which was originally an English company until an office was established south of Los Angeles in Vista, CA in 1982, becoming independent in 1991 improved on the technology and took it to a professional level. But the market was small.
The critical turn came in 1984 when Apollo Sprayers submitted independent laboratory tests to SCAQMD demonstrating that their turbine system could produce over 80percent transfer efficiency the ratio of the amount of finish left on the work surface to the total amount sprayed. The Turbo Spray System, as it was then called, produced a soft spray that left far less solvent to be exhausted into the atmosphere.
It was SCAQMD that came up with the name high-volume, low pressure and its acronym HVLP.
Around 1986, SCAQMD began requiring the use of HVLP or other technology that produced at least 65 percent transfer efficiency. Sixty-five percent transfer efficiency is approximately double that of the traditional high-pressure technology.
Thus was created a market for HVLP beyond just its advantage in wasting less finish. Aided by positive articles in woodworking magazines, the market quickly spread from Southern California to the rest of the country and, indeed, to most of the world. HVLP is just a better technology.
Apollo Sprayers not only helped get HVLP technology started; the company also pioneered many advances in this technology, including 100percent stainless-steel fluid components (for water-based finishes), more powerful turbines (now with dial-in air pressure), flexible attachments for the thick, unwieldy hoses, and a spray gun that can be used with either a turbine or compressor and in all three popular configurations, cup mounted below the gun, cup mounted above the gun and separate pot connected by a fluid hose.
Compressed Air HVLP
For a while, the only available air source for HVLP spray guns HVLP is defined as 10psi or less at the air cap was a turbine, which consisted of one or more impellers, or fans. So it was only natural for the term HVLP to come to mean a spray gun powered by a turbine.
Manufacturers of high-pressure spray guns supplied by compressors also wanted to participate in the HVLP market, so they figured out how to re-engineer compressed-air spray guns to spray at a soft 10psi or less at the air cap. They did this by converting the high-pressure air to high-volume air within the spray gun.
It took awhile to improve the technology so it equaled the quality of high-pressure spray guns. Through most of the 1990s, for example, discriminating auto-body finishers resisted the new technology because it left more orange peel. But by 2000 or so, the technology had improved enough so that most had switched to compressed-air HVLP. Turbine-air-supplied spray guns never caught on big in auto-body shops, maybe because they already had large enough compressors to power the compressed-air guns. But turbine HVLP is widely accepted for its portability.
At first, the spray guns that converted high-pressure air from a compressor to HVLP were called conversion guns. You may still run into this term. Slowly the names have changed to the more logical compressed-air HVLP and turbine HVLP to distinguish the two air sources. Conversion refers now more to a gun’s ability to work off both turbine and compressed air.
Both air sources produce HVLP and both are capable of producing good results, equivalent to high-pressure spray guns. So the market for high-pressure spray guns has virtually disappeared. These guns have even become difficult to find.
Apollo's demonstration of HVLP technology to SCAQMD has led, in a quarter century, to an almost total transformation in the type of spray guns used.