Woodworker's Journal 1985-9-5, страница 21

Spray finishing can help impart a real professional look to your | projects and increase your efficiency on large finishing operations. : I've had an air compressor for some Ji time, but I've never used it for spray- I ing. Lacking enough space for a dedicated spray area means that 1 would have to spray in the middle of .■'= my small shop. And it's the thought of the clouds of overspray covering j| everything else in the shop that has really prevented my enthusiastic leap toward spray finishing. With that in mind. 1 was really inter- | ested in the new Finecoat high volume low pressure (HVLP) sprayer from Wagner.

WAGNER FLNECOAV

SPliAl'ELi

by Dennis Preston

WAGRER

FineCoat

"hi

Why HVLP?

High transfer efficiency is the main selling point of HVLP. Transfer efficiency is the percentage of the finish sprayed that is actually deposited onto the work surface. Conventional spray guns require high pressure (about 40 psi @ 8 CFM) lo atomize and propel the finish onto the work. The pressure produces very fine atomi/ation, causing a large portion of the finish lo remain airborne. Overspray is the airborne finish that settles elsewhere.

Instead of pressure, HVLP sprayers use high volume air How and low pressure (about 4 psi @ 47 CFM from a shop vacuum type blower) to produce a fine mist. This results in less overspray and more finish ending up where you want it.

Because of the low pressure. HVLP systems are intended lot use with light bodied (low viscosity) finishes. These include stains, water based varnishes, lacquer, and thinned polyurc-thane and enamel paints.

The Finecoat

The Finccoat comes complete in one package that includes the blower unit, a 15 ft. hose, the spray gun. viscosity cup. blower nozzle and instructions. The instructions are clear and. if you need assistance, there's also an 800 number help line available.

After reading ihe instructions. I swept up a 6 fi. by ft ft. area to try the sprayer. Because the air delivery (and noise level) is like a shop vacuum exhaust, you should remove as much shop dust as possible so that it isn't blown onto the work.

There arc two adjustments on the spray gun: a knob that controls the amount of fluid flowing to the nozzle, and the orientation of the spray cap. w hich determines the pattern. You can select a round pattern, or a vertical or horizontal Ian pattern.

Ijft Us Spray

To prevent clogging the nozzle. I strained each finish and checked the viscosity before pouring it into (he spray gun

September/October 1992

container. The stain and the water-based varnish didn't require thinning, but the solvent-based polyurethane needed to be I thinned with mineral spirits before use. In general, coverage and uniformity are dependent on your spray technique. It's important to keep the gun moving .it a uniform rate and to always hold it perpendicular to the work surface. To further control ihe coverage and limii overspray. you can hold the nozzle from I lo 12 in. away from ihe surface. Most of my testing w as at |. about 12 in. from the work.

After some trial lests on cardboard to get the feel of the sprayer, I shifted lo wood. To lesl the partem uniformity, I sprayed waier stain onto a pine board. The stain, actually an aniline dye. is one of the most difficult stains lo apply without lap marks and bloichiness. The results were very good—better than I could have done "" with a rag in the same amount of time. I next tried Carver-Tripp SuperPoly water-based polyuielhane. The results were also very good. The fan pattern helps deposit a uniform layer w ith little overspray.

Aftei a quick water clean up and thoroughly drying the spray gun I tried solvent-based polyurethane varnish. After ihinning tin- polyureihane with mineral spirits and adjusting the material flow knob. 1 tried tesl patterns on some pine and oak. The |H>lyurethane sprayed neatly and covered well but did not level as quickly as the water based poly. This may either be ihe nature of ihe varnish or that I didn't thin it enough.

Although ihe Finecoat w ill also spray conventional lacquers. I'd recommend staying with the clean water-based finishes to avoid the combustibility and health hazards of lacquers.

Clean-L'p

Only the gun requires cleaning. Dump the remaining finish back into the can. Wash out the container and nozzle with inappropriate solvent. I'd prefer a larger opening in the mouth of the material container to make it easier to clean with a rag. The water-based finishes were the easiest to use and clean up.

Summary

I was impressed with the Finecoat. It provided good uniformity and control. There was no detectable overspray beyond my cardboard backstop. While most of the Finecoat system is plastic (except for ihe nozzle assembly), because of the low pressure nothing seems to be highly stressed, so it should give long service.

For more information, contact Wagner Spray Tech Corporation. 1770 Fernbrook Lane. Minneapolis. MN 55447; tel. 1-800-328-8251. The current price is S179. O

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