Spraying Polyurethane Oil based

[Jim German]

I've been trying to spray some semi-gloss Minwax oil based "fast drying" polyurethane. I've been using the Kobalt Small Gravity gun and having a ton of trouble. I seem to have alot of difficulty getting the finish on right, its always either to light and doesn't make a nice film, or its to thick and it drips. Some of my issues are defintly technique related, and I've had some issues with not cleaning the gun well enough too. However after sanding off the crappy finish for the like 10th time I'm beginning to think I should try a different gun. I'd like to try and get something tommorw, so online is out. Therefore does anyone know if the Husky HVLP gun from HD is any good? or if Woodcraft has a nice gun or anywhere else in the Philly/NJ area? I've got a good sized compressor.

[Curt Harms]

I don't have that gun so I'm just speculating here. Most oil based polys are a little thick to spray straight out of the can. Have you tried thinning a little? If this is a 'fast drying' I wonder if they're using something like naptha instead of mineral spirits to adjust the viscosity. The proper way to measure viscosity is with a viscosity cup but I read about a technique I think from Bob Flexner that works pretty well for me. Dip a stir stick into the finish, wait a second and lift. The material should come off in a stream, not as drops until it's nearly all off. Travel speed also enters into it. Move too fast and the finish it too thin and dry, too slow on a vertical surface and it'll run. I haven't sprayed oil based anything in years so am not much help, I'm afraid.

[Howard Acheson]

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[Jim Becker]

Jim, an oil based finish isn't the best product to spray, even once you get your gun dialed in to shoot it well. Why? Oil based finishes dry slowly and the best spray applications use fast drying products. A slow drying finish will have very sticky overspray and the time intervals between coats have to be spread out to the point that you potentially can be needing to clean your gun between coats in some circumstances. In general, oil based finishes are best brushed or wiped on. They level well due to the slow dry time and you can "work" them longer, too.

Once you spray a product that was designed for spraying or is more readily adaptable to spraying, you'll wonder what you were thinking!

[sheldon pettit]

I've been trying to spray some semi-gloss Minwax oil based "fast drying" polyurethane. I've been using the Kobalt Small Gravity gun and having a ton of trouble. I seem to have alot of difficulty getting the finish on right, its always either to light and doesn't make a nice film, or its to thick and it drips. Some of my issues are defintly technique related, and I've had some issues with not cleaning the gun well enough too. However after sanding off the crappy finish for the like 10th time I'm beginning to think I should try a different gun. I'd like to try and get something tommorw, so online is out. Therefore does anyone know if the Husky HVLP gun from HD is any good? or if Woodcraft has a nice gun or anywhere else in the Philly/NJ area? I've got a good sized compressor.

First off, it's a matter of what your spraying. horizontal work should be no problem getting a nice poly finish, especially with the fast dry poly. Like others, i'm not familiar with the particular gun your using but i would say any gun that has a 1.2-4 mm fluid tip should easily spray any urethane with no problem. Even under 1mm can be used if the material is thinned down sufficiently. I have to agree with you that Spray techniques and a clean gun are probably why your having most of your difficulty, aslo, you may not be making samples and testing your settings so that you know your project will look just like your hoping it will when you are finally ready to start spraying it. Since you have not mentioned just what it is your spraying i can offer little more than this sorry.

[Howard Acheson]

>>>> I've been trying to spray some semi-gloss Minwax oil based "fast drying" polyurethane.

This is the Minwax product the OP is probably referring to: http://www.minwax.com/wood-products/...g-polyurethane

[Jim German]

I ended up buying the QualsprayQS-125WB with a 1.2mm tip, and to be honest I really haven't noticed much of a difference between it and the cheap $30 Kobalt gun. I eventually gave up trying to spray the oil based poly, didn't seem to matter what I did, if I put it on thick enough to form a film, it dripped. I tried some of the Minwax Polyacrylic water based polyurethane and it worked much better. I'm worried about the durability of the waterbased poly though.

Looking into it more and I think I'd be happier with a catalyzed laquer. Anyone have a favorite of those?

[Ron Natalie]

While I haven't done this particular minwax product, I've used my HVLP gun with pretty good success thinning down and adding a touch of Penetrol.
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