Spray poly over hand-applied poly

[Mike Wilkins]

I am in the last laps of finishing a audio cabinet and using hand rubbed poly. As you can guess, it is slow-going. Any problem switching to a couple coats of sprayed poly??? Thanks.

[Howard Acheson]

You can spray an oil based poly over a brushed poly. However there are a couple of caveats: First, just as you would if you were brushing on a new coat, you must scuff sand the existing surface with 320 paper to ensure good adhesion of the sprayed coat.

Second, spraying an oil based finish is problematic in that the finish is so slow drying. This means that the overspray is in the form of liquid droplets that will float in the air coating everything in the area with crust of dried finish.

Finally, I don't know what you mean by "using hand rubbed poly". Does that mean you are attempting to sand, level a dried poly finish or do you mean you are wiping on the poly instead of using a brush? Polyurethane resin is added to an oil based finish to increase it's resistance to scratching. Sanding or "rubbing out" is scratching and poly does not respond well to being abraded with fine sandpaper. In general, poly will never be more glossy that it is right off the brush or just sprayed.

[John TenEyck]

As Howie said, spraying OB poly is going to make a mess on anything the over spray hits. I'd just suck it up and keep applying more coats like you've been doing. Much less headache.

John

[Mike Henderson]

Or apply a coat of dewaxed shellac and then shoot lacquer. The shellac between the coats will guarantee adhesion.

Poly has certain advantages over lacquer (and certain disadvantages) but I don't think it's necessary on an audio cabinet.

Mike