putting finishing over an unknown finish

[John Hollander]

I just bought a used desk that has some of the finish chipping/peeling off the top. I don't want to completely strip the desk. Can I chip off the loose parts and steel wool the top and put on a few coats of urethane or polyurethane without having any problems? I know it won't look perfect but I just want the top to be completely sealed.

[John TenEyck]

Sure, you could, but most any finish will come off in short order with stripper, and it's pretty darned simple to do. This stuff works great and has almost no smell: http://www.homedepot.com/p/Klean-Strip-1-gal-KS-3-Premium-Stripper-GKS3/100144685#.UcjaNJzTCs4 So strip it. Either way, I'd suggest you give it a coat of dewaxed shellac, like SealCoat, before applying your topcoat. That will give you a good bond layer between the top and any topcoat.

John

[Howard Acheson]

If the existing finish is failing as you describe, it would not be a good idea to over coat it with another finish. A new finish on top of the existing will not improve or keep the old underneath finish from continuing to lose adhesion. In addition, poly varnish has reduced adhesion and may not adhere well to the old finish. Finally, you don't know what the original finish is/was or what oils or polishes have been applied over time.

For all the above reasons, to end up with a good job, you should take the time to strip off the old finish and then apply your new finish.