Furniture, Wood and Cabinetry Finishing - Uneven poly finish
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Zathrus
08-14-02, 02:19 PM
I previously asked about sanding between poly coats - thanks for the help on that. Unfortunately the first piece came out a bit rougher than we would've liked. The stain is ok in most spots, but the poly is very uneven. It's an oil-based satin poly, but it turned out streaky and has different glosses in different areas.
So what'd I do wrong? The pieces are unfinished alder. We did apply a preconditioner, two coats of stain (24 hours+ between coats), and two coats of poly (24 hours+ between stain/poly/poly). Not enough stirring of the poly? Too much attention when brushing on? Any ideas?
I have another three pieces to do, all sanded and ready, but I'm afraid to actually start staining until I can figure out what I did wrong on the first piece!
On a related note, there are bits of "gunk" in the finish -- I forgot to wipe the piece down between coats, so I suspect that I brushed stuff into the finish and sealer. Sound right?
So what'd I do wrong? The pieces are unfinished alder. We did apply a preconditioner, two coats of stain (24 hours+ between coats), and two coats of poly (24 hours+ between stain/poly/poly). Not enough stirring of the poly? Too much attention when brushing on? Any ideas?
I have another three pieces to do, all sanded and ready, but I'm afraid to actually start staining until I can figure out what I did wrong on the first piece!
On a related note, there are bits of "gunk" in the finish -- I forgot to wipe the piece down between coats, so I suspect that I brushed stuff into the finish and sealer. Sound right?
George
08-14-02, 07:59 PM
You're right about the debris in the finish - probably improper cleaning after sanding. Cleaning is very critical in poly and varnish - not so much so in lacquer and shellac.
The variation in the sheen is due to incomplete stirring of the poly before application. The natural condition of most finishes is gloss; additives tone the sheen down to semi-gloss, satin, or flat, but those additives will settle out.
Stir the poly continuously for at least five minutes before starting, and every 10 minutes after that.
Over brushing will show up as brush marks left in the finish after it dries; if that's not apparent, don't worry about your application technique, except for stirring the poly.
The variation in the sheen is due to incomplete stirring of the poly before application. The natural condition of most finishes is gloss; additives tone the sheen down to semi-gloss, satin, or flat, but those additives will settle out.
Stir the poly continuously for at least five minutes before starting, and every 10 minutes after that.
Over brushing will show up as brush marks left in the finish after it dries; if that's not apparent, don't worry about your application technique, except for stirring the poly.
Zathrus
08-16-02, 07:08 AM
Thanks for the reply George.
I guess the next question is, is there anyway to fix the piece that's already "done"? Will putting another coat of poly on (after stirring sufficiently) even out the finish?
What about the junk in the finish? I'm guessing that the only way to fix that is to sand back down until the junk is gone. "Fortunately" the only place this is particularly visible is the top -- so it wouldn't be too hard to redo.
I guess the next question is, is there anyway to fix the piece that's already "done"? Will putting another coat of poly on (after stirring sufficiently) even out the finish?
What about the junk in the finish? I'm guessing that the only way to fix that is to sand back down until the junk is gone. "Fortunately" the only place this is particularly visible is the top -- so it wouldn't be too hard to redo.
George
08-16-02, 06:39 PM
You're right about the 'junk removal' - sand it out.
What many fail to realize is the sheen of the finish is in the last coat applied; so the answer to your other question is yes. Another coat (properly stirred) should result in an even sheen.
I finish a lot of pieces in lacquer, mainly because I'm dealing with older pieces and am somewhat of a traditionalist. I always use gloss lacquer, even if the finish look is to be semi-gloss, or satin.
Gloss lacquer (as well as polyurethane, BTW) has no sheen altering additives. I can pop open the can, apply a coat, clean up the brush, and go away - never have to stir. I 'adjust' the sheen down from gloss with steel wool after the finial coat.
What many fail to realize is the sheen of the finish is in the last coat applied; so the answer to your other question is yes. Another coat (properly stirred) should result in an even sheen.
I finish a lot of pieces in lacquer, mainly because I'm dealing with older pieces and am somewhat of a traditionalist. I always use gloss lacquer, even if the finish look is to be semi-gloss, or satin.
Gloss lacquer (as well as polyurethane, BTW) has no sheen altering additives. I can pop open the can, apply a coat, clean up the brush, and go away - never have to stir. I 'adjust' the sheen down from gloss with steel wool after the finial coat.