Which HVLP spray finishing system is right for you?
“Don’t be afraid of spray finishing,” were the first words of advice from my good friend, fellow woodworker and coatings expert Julian Hay, who is also the president of Associated Coating Services. Hay has sprayed just about everything from jewellery boxes to oil refineries. Hay continued, “Get some drop cloths and a box fan with a furnace filter over it. Then get a bunch of cardboard or scrap MDF and start spraying it. It’s like learning any other woodworking skill: get out the scrap and make your mistakes on it. Get out the good wood once you stop making mistakes.”
Good advice, I would later learn.
Lots of Benefits
An HVLP system puts the majority of the finish material on the work-piece, as opposed to putting it into the surrounding air. Good for the environment and your pocket book. (Photo by Apollo)
The Full Range of Finishes
Perry sprayed latex paint, deck stain and a waterborne alkyd varnish in order to get a good idea of what each system was capable of.
In any Position
Instead of using the typical spray cup, the Lemmer spray gun uses 3M’s Paint Preparation System. This allows the gun to be used at any angle, including upside down.
Small, But Important Details
The Lemmer system is equipped with a stainless steel spring that fits over the hose. Their hose also has an internal moulded spiral rib that protects the integrity of the hose.
Many of the systems use a connector that is a smaller diameter than the hose. This potentially causes a reduction in air pressure at the gun. The Earlex system (far right) is the only system that doesn’t use a smaller diameter connector.
With the systems loaded with finishing material Perry started spraying pieces of cardboard. He got an idea of how the different systems performed without wasting lots of expensive material.
It All Depends
What you plan to spray with your HVLP system will help determine what system is right for you. If outdoor furniture makes up most of your work then you need not break the bank. (Photo by Wagner)
The Perfect Finish
If you’re looking for a top-rate finish, a higher end system is more appropriate. This humidor, by Ryan Shervill, is the perfect example of where a quality system makes sense. (Photo by Eddie DeJong)
Why use HVLP?
HVLP evolved because conventional spray systems, while effective for atomizing finishes, are far from efficient.
Their average is to put about one-third of the finish onto the work-piece, with the other two-thirds in the atmosphere. In contrast, an HVLP system puts about two-thirds or more of the finish onto the work-piece and a third or less ending up in the air.
This is good for a couple of reasons. First, it’s good for the environment (whether our government cares or not). Second, it’s good for your pocketbook. When you stop blowing two-thirds of your finish out the window, the savings add up fast.
What makes HVLP more efficient?
A spray gun uses air to atomize a finish, which means that it breaks it into a mist. With the proper balance of air pressure and coating viscosity, combined with the distance of the gun from the surface being sprayed and the speed of application, that mist will condense back into a smooth, even coating that both protects and beautifies.
A conventional spray gun needs about 50 PSI at the inlet from the compressor, and it will still have 50 PSI at the cap, where atomization takes place. That wastes a ton of paint through overspray and blowback. (Blowback is when paint hits the surface so hard that it bounces back, leaving an uneven surface.)
An HVLP gun, on the other hand, will have less than 10 PSI at the cap. That’s because its air supply comes from a low pressure turbine instead of a high-pressure compressor.
To confuse matters, there are conversion HVLP guns, which are used with a regular compressor, and turbine HVLP systems, which are self-contained units comprising a gun, a turbine and a hose.
To keep the length of this article manageable, I’m limiting it to turbine HVLP systems.
I’m also leaving out solvent-based finishes, as government and industry move toward removing these from the market. With these changes underway, it’s worth a quick review of some nomenclature so we know what we’re working with.
Ask your average woodworker what kind of finishes are available and chances are you’ll hear “oil-based and water-based” as an answer. It’s not quite so simple. “Oil-based” is more accurately called “solvent-borne,” while “water-based” coatings can be either “water-based” or “water-borne.” So what’s the difference?
Water-borne finishes are blended using a solvent base. They can be thinned and cleaned up with water, but in fact combine oil, water, resins, and various additives to control the sheen, viscosity, flow-out, colour and so on. They have a limited shelf life and, if frozen, are probably ruined.
Water-based finishes use water as their solvent, along with the various resins, additives, etc. that make up a finish.
Their shelf life is longer, they can withstand a few freeze-thaw cycles and they’re lowest in VOCs (volatile organic compounds, a.k.a. nasty fumes).
Either water-borne or water-based should perform equally well. However, either product must be properly formulated to reflect its method of application. And although most manufacturers will state “Can be sprayed” on the label, what you really want to find is “RTS,” which stands for “Ready to Spray.”
A finish to be manually applied by brushing or wiping will have a different blend of additives than one formulated for spraying. That’s because the two application methods dry differently. This is often overlooked.
Before committing to a finish for your next project, it’s worth a call to the coating manufacturer’s customer service department – not to the store where you bought it – or to a knowledgeable distributor such as Wood Essence Distributing. Ask for their advice about RTS products and describe your project and spray system. Good advice goes a long way.
From time to time you will almost certainly spray finishes that are formulated for brushing, since they are the ones most available in the DIY market. So I decided to break a few rules here and use the HVLP units to spray finishes, whether they were intended to be sprayed or not, particularly latex emulsion.
Also, this is not a head-to-head tool review, so please consider each unit based on its own capacity and features relative to the job you have to do. That should help you decide what you need both in terms of equipment and materials.
Instead of using a tank of pressurized air, an HVLP system uses a turbine to provide warm, clean air to atomize the finish being sprayed. It is made up of a series of fans, called stages, that move large volumes of air at low pressure, much like a vacuum cleaner.
Although other factors such as motor speed and turbine blade design will affect a system’s output, the number of stages provides a quick gauge of its power.
The HVLP spray gun has controls for fluid flow and spray pattern. Most systems will also have an airflow control either on the turbine or the end of the air line. Guns that have a control for fan width allow you to adjust the shape of the spray pattern from round to a narrow ellipse. Some models permit basic adjustment (round, horizontal or vertical fan shape) by turning the air cap, but an adjustment knob or ring gives better control.
Although the hose may seem to be the least important piece of the package, it does need to be light, strong and flexible. A heavy hose is tiring to drag around, and if it’s stiff it restricts the movement of the spray gun. Some systems include a pliable “whip” section of hose at the business end to improve flexibility.
Hose length can also be a factor if spraying solvent-borne lacquer or other potentially explosive finishes. Motors that power the turbines in HVLP units are not explosion-proof, so place the turbine as far as possible from where you are spraying.
Kinks or bends in the hose restrict airflow, causing back-pressure, which degrades performance and increases heat build-up. The turbine’s motor generates heat, so adequate ventilation is vital.
Motors also generate noise – about the equivalent of what you’d get from a shop vacuum. But don’t be tempted to place a turbine into another box to muffle the sound. Without proper ventilation, the motor will overheat.
As with many tools on the market, HVLP systems have a confusing array of features and prices. To help you make some sense of this, we decided to look at five different price and performance levels of machine, and to select one representative system from each of five manufacturers. We would then use each of the systems to spray Home Hardware’s Wood-Shield water-borne semitransparent deck and fence stain, their Beauti-Tone brand of latex (emulsion) trim paint, and Target Coatings’ Emtech™EM2000 water-borne alkyd varnish, supplied for the test by Wood Essence Distributing.
The idea was not to make a head-to-head comparison of the HVLP systems and determine a “Best in Show.” Instead, it was to spray three finishes that might typically be used in a home shop, using systems of varying capacities, to get a picture of what you might expect when using them yourself.
Also, I know that some of you (us?) will attempt to spray a finish that was never intended to be sprayed – such as heavy latex (emulsion) paint – using a system that has nowhere near the power required to spray it – such as a one- or two-stage turbine. So we went ahead and tried that too.
What you get: a snapshot of each system
Lemmer T90Q – Four-stage
The Lemmer system features a four-speed turbine, 25′ air hose and air control valve. Its excellent quality non-bleeder spray gun with fan control comes with 1.3mm needle installed and 2.0 mm needle/nozzle set included, a 250ml detail paint container and viscosity cup. Reducing the speed when full power isn’t needed makes this very quiet machine even quieter. It also cools the air supply, which can help when spraying latex or lacquer. The gun uses the 3M PPS™ Paint Preparation System (a hard plastic outer paint cup containing an inner plastic liner and cover that hold the finish being sprayed). (Photo by Lemmer)
$1,500.00 direct from lemmer.com
Apollo Sprayers 1050VR – Five-stage
Apollo’s 1050VR turbine unit comes with an auto variable turbine speed/air pressure control and LCD pressure display, 20′ air hose with 4′ flex hose (⅝” hose instead of the ¾” on other suppliers’ units, for less weight), 7500 Series non-bleeder spray gun with 1.3mm needle set installed, 1 litre pressure cup and 250ml detail cup, paint filter stand. Spray gun set includes gun, five sets of fluid nozzles and needle assemblies, three air caps, spare gaskets, wrench, cleaning brush and lubricant. Gun is made of stainless steel, paint cup made of Teflon-coated aluminum. (Photo by Apollo)
$1,599 at amazon.com
General observations and comparisons
Each price level of system features incremental improvements in capacity and quality. For example, the Wagner is made of moulded plastic; the others are metal. Earlex uses a cast aluminum gun and air cap with stamped trigger; these parts are machined in the Fuji, Lemmer and Apollo guns. The Lemmer has a machined aluminum gun and a manual four-speed turbine control; the Apollo has a machined stainless steel gun and an automatic speed control. Lemmer is unique in using 3M’s PPS Paint Preparation system instead of paint cups. The PPS setup actually allows spraying with the gun held in any position, including upside down.
None of these steps up are necessarily deal-breakers. Hay and I tried out each system with ergonomics and functionality in mind and found little to complain about.
We also checked the sound levels of each unit using a decibel meter, held six feet away from the turbine with the hose and gun connected. These readings gave us a semi-objective comparison of how much noise to expect.
The Wagner Control Spray was quietest. It sounded like a hair dryer and it didn’t even register over the background noise of the exhaust fan we were running. The other units scored as follows:
The meter confirmed our subjective impressions. The Earlex and Apollo were both audible over the sound of the exhaust fan, but not bothersome – similar to the sound of a vacuum cleaner but not as loud as a Shop-Vac. The Fuji and Lemmer systems stood out – the Lemmer for the amount of noise it didn’t make, and the Fuji for the amount it did.
The Fuji was loud enough that I’d consider wearing ear protection; the Lemmer was so quiet that at six feet away, over the exhaust fan’s noise, I couldn’t tell when it was turned on.
While inspecting the systems, we noticed that the Fuji, Lemmer and Apollo units all used connectors smaller than the diameter of the air hose. That surprised us since any air or vacuum system should be free of restrictions and obstructions.
Only the 1-inch diameter Earlex hose has no extra fittings or size restrictions. It plugs into both the turbine and gun with a friction fit. This may contribute to the Earlex’s surprisingly good performance; it’s almost like getting an extra turbine stage by reducing back-pressure.
With any unit, pay attention to the hose where it connects to the turbine. The Fuji’s hose was prone to kinking in spite of a larger diameter rubber sleeve that fits over the connection. Lemmer uses a better system with a stainless steel spring that fits over the hose, plus their hose has an internal moulded spiral rib that prevents it from being kinked or flattened.
How we tested
We had to make some arbitrary choices about spray-gun setup. The first had to do with the size of the nozzle and needle sets we used. The Wagner doesn’t have interchangeable nozzles so no adjustment was possible; however, the needle measured to be 2.0mm.
We used the standard 1.4mm nozzle in Fuji’s gun and the closest match to that – 1.3mm – in the Lemmer and Apollo guns. The Earlex gun comes with 0.8mm and 2.0mm nozzles; we chose the 2.0mm to make up for the lower power of the Earlex two-stage turbine when compared to the others, and to better match the Wagner.
Next we checked viscosity. The Wood Shield waterborne stain took 24 seconds to run through a Zahn #2 viscosity cup. The Emtech waterborne varnish took 34 seconds and the Beauti-Tone latex emulsion paint took more than a minute.
We used the stain as our baseline and sprayed it first, without thinning. Each system handled it well and it also gave us a clear picture of the spray pattern from each gun. This boosted our confidence enough to try the varnish, also without thinning.
Once again, each system handled it well. But how much would we have to thin the latex?
When thinning latex emulsion you want to (a) lower the viscosity so it sprays and (b) extend its drying time so it levels. But you don’t want to overdo it; otherwise, all of its nice “painty” attributes disappear and using it becomes as gratifying as spraying skim milk.
First, use water to lower the viscosity (thin the paint), then use a conditioner like Floetrol, DynaFlo, or Target Coatings’ SA5 retarder to extend its drying time. Hay thinned the latex in a 5:1:1 paint:water:conditioner ratio, which lowered its viscosity enough to run through the Zahn cup in 30 seconds after mixing and filtering.
How they performed
The big surprise was how well each system did. Frankly, I thought this was going to be like throwing mud at a wall: the wall gets covered but nobody could call it pretty. Instead, every system managed to spray every finish, with some limitations.
Atomization is a function of pressure and viscosity: high pressure plus low viscosity gives good atomization, while low pressure plus high viscosity yields poor atomization.
This became apparent with the Fuji, Lemmer and Apollo systems. Their greater power permitted better control, mainly in the “fine-ness” of the atomization. The more powerful systems were capable of almost “fogging” the finish onto the surface; the lower-powered ones had spray patterns that were more “splattery.”
Since the Wagner lacks an air pressure control and the nozzle/ needle is fixed, you set the fluid control and then how much finish you apply depends on your speed of application and the distance of the gun from the work.
It’s similar with the Earlex. Using some cardboard as a target, adjust the volume of finish to be sprayed, then turn the air cap and ring to adjust the size and pattern of the spray. Fine-tune the volume of finish, then vary the speed at which you move the gun and its distance from the work-piece to control the finish thickness.
While getting a “feel” for the varnish, we sprayed coats with the Wagner and with the Earlex that were heavy and “wet” enough that we expected them to run and then to dry with a heavy “orange peel” pattern. Neither happened. The Emtech varnish levelled and dried beautifully. The more powerful systems with better adjustments on the gun gave even better control in laying down multiple light but wet coats that levelled into a first-rate finish.
I must admit we doubted that the latex emulsion was going to spray at all. This is thick stuff. But after thorough stirring and filtering we’d blended in the water and reducer and had a very smooth paint.
The Wagner and Earlex systems will spray this, but I’d recommend that you be careful about masking before you start. With the larger nozzles there is a fair bit of overspray and blowback plus they spray a heavy coat so you have to keep the gun moving. If you hesitate you’re risking runs and drips.
Frankly, a good painter can paint a room’s trim with a brush in less time than it would take just to mask everything, so I’d question the wisdom of spraying. You can obtain very fine atomization that levels down to an excellent finish from the three more powerful units, but you still have to mask. Plus, don’t think that you’ll get away without some kind of spray control and filtration. There may be little overspray, but what there is goes everywhere if you don’t control it.
Now ask yourself, “Will I get better results by spraying?” “Will spraying save me time?” “Will I do enough work to justify the purchase of an HVLP system?” and “How much do I need to spend to get the quality I want from HVLP?”
Answering those will make your choice quite simple. Each of these HVLP systems does a good job on the work for which it was intended. Just choose rationally. You probably don’t need to spend a thousand dollars to spray-paint your fence. But neither is a $100 unit likely to give you the finish quality you want for your humidors or jewellery boxes. So spend the hundred bucks on your fence and invest the thousand dollars on finishing your humidors.
Recently, I had two rattan deck chairs in need of refinishing and I considered how long it would take. Staining them with a brush is a very picky two-hour job. Spray finishing took seven minutes. That’s what you call a no-brainer.
The lead photo shows Bill Perry spraying a small chest without wearing a protective mask or goggles. What the photo doesn’t show is a 1500 cu. ft/min. exhaust fan, just out of the picture to the right, channeling overspray (from a waterborne finish) out the open back door of his shop. Both mask and goggles should be worn whenever spraying a finish.