Spraying Polyurethane

[Mike Hill]

Has anyone had success spraying poly? If, so, can it be thinned with mineral spirits for use in a spray gun?

I prefer lacquer, but with no spray booth, I have to spray outdoors and here in Texas there is usually too much humidity for spraying lacquer, even with some retarder in it.
Mike

[Howard Acheson]

Any liquid can be sprayed. How thin it must be is determined by your gun and compressor.

Spraying any oil based finish is problematic due to its slow drying. The overspray is a liquid mist which settles on anything in the area and dries to a crust. It's best to spray outside or to use a spray booth. Outside, of course, leaves you at the mercy of any dust or other junk in the air.

If you are interested in spraying, you might want to purchase Andy Charron's Spray Finishing. It will discuss equipment, finish types and thinning and it will also give you lots of info about application techniques.

[Loren Hedahl]

I spray it, usually with a small somewhat cheapo Harbor Freight HVLP detail gun.

I don't like to thin with any old painters thinner. Most times I don't need to thin at all. It usually sprays great just out of the can once you get your gun adjusted. When a small bit of thinning is needed, I get better results with automotive grade enamel reducer, especially when I want high gloss.

I always strain into the gun. Rather than use the commercial strainers, I have a small wire mesh kitchen strainer from the dollar store that works fine.

For gun and strainer clean up I use painters thinner. Then follow up with a small amount of reducer, or brush cleaner.

Works for me. Your mileage may be different, but you're welcome to give it a try.

Loren

[Mike Hill]

Thanks Loren and Howie: I have a Porter Cable HVLP gravity gun and a Husky 80 gallon compressor. Plenty of air :) Will give it a try outside. Supposed to be 60 tomorrow, so I can probably spray.

Mike

[Howard Acheson]

Be careful about the temperature when you spray. 60 degrees is pushing it. It can lead to running and sagging. Below 55 degrees and the finish may never cure. You need to keep the sprayed item at above 60-65 degrees for as long as it takes to cure which can be up to 3-4 weeks for oil based finishes--particularly at temperatures below 70-75 degrees.

[Matt Meiser]

I've used the Minwax WB poly on a few things lately and really like it. I'm using the same gun as you. I've been spraying it right out of the can. I added about 6 drops of trans-tint honey amber dye to make it look like oil-base when dry and have been happy with the results. I used it on utility projects, but others have told me they used it on things like book shelves, stair treads, and bath vanities.

[Jim Becker]

Spraying the water borne poly is very different than spraying the oil-based poly. The former is pretty much like any water-borne; dries fast and you can recoat frequently. The latter is not something I'd do just due to the sticky mess, even with HVLP.

[John Mihich]

Have sprayed it a few times. I use napha to thin it; a little quicker drying. I do cover everything that's in sight. Poly will stick while lacquer and shellac just create a dust.