Okay, I've built an island for my kitchen with a 4'x5' tabletop. I had a couple coats of poly on it and decided to put another on for added protection. The last coat I put on (Minwax fast drying poly-not water based) seems to have tiny bubbles in it....really tiny. I didn't shake the can, just stirred it gently. The first couple coats didn't do this and I used the same product. Any way I can smooth this out without having to put another coat over top and creating an endless cycle of steel-wooling, putting more on seeing bubbles and doing it all again? I think it's got enough coats on that if I could just kind of "polish" the last coat, it'd be fine.
Get some wet or dry sandpaper, Lorraine. 600 grit or higher. Use a very little bit of water and a sanding block. Let the water become a lubricant for the poly - allowing it to turn into a slurry. Don't allow it to dry - keep adding water as necessary to keep it wet and use ONLY the weight of the sanding block to smooth the poly. If done properly, you can achieve a glass-like surface on the tabletop. I've used poly almost exclusively in my furniture building and the results will astound you. If you over sand, just re-apply another thin coat and start over (making sure that the coat has completely dried and cured.
Get away from Minwax products and fast drying. The bubbles normally form as you apply the finish, and if the finish dries too fast the bubbles get trapped before they disipate. Take a look at General Finishes products such as Arm-R-Seal.
Jim, I'm curious how you're achieving a highly polished finished with poly. Are you progressing past the 600 grit? I have a table that I finished with water-based poly. I did finish sanding with 600 and 1000 grits, followed by pumice then rottenstone, and it still didn't get glass-smooth. I think I also tried some 2000 grit paper that didn't help much. Maybe just not enough elbow grease with the rottenstone?
I put a Maple top on a kitchen vegetable storage cabinet and finished it with about 4 to 6 coats of water-based poly. The between-coat sanding started at 220 and ended at 600 {if I remember correctly}. It may have been only 400. The coats were laid down with a cheap foam brush, with the last 'wiped' on with a piece of old 'T'-shirt material. A couple of coats of well-buffed wax completed the job.
Still 'Glass Smooth' after a couple of years as Joanne's 'table-side utility space & lamp shelf'.
Neal, Higher grits is the the but 1000 and then 1500 should do it. I use wet/dry paper and as lubicant use the thinned poly (a 50/50 mixture with naptha or min spirirts.) The rubbing is very lightly done and after a little while, let it dry as you rub...not all the way but almsot all the way. The sanding stuff should be filling the surface ever so lightly. At end, wipe off carefully and let fry. You should see quite an improvement each time. You can take it to whatever level as you wish.
I've never done this, but have sanded fiberglass composites and plastics.
You wouldn't expect a smooth finish (meaning glasslike) with just 1500 sandpaper. That would be fine for a frosted finish (maybe), but not for a gloss. You'd have to go higher. To get a real polish on plastic, I have to go with a rubbing compound and a polishing compound. That's much finer than
1500 sandpaper. It takes a lot of elbow grease, too.
It sounds like your solution using the thinned poly as a wetting agent is "cheating". That is, you are making small scratches with the sandpaper, but filling it with poly right away. If you do a "rough" (not glossy) sanding job and then coat with poly, the poly will fill the scratches and clean up the surface. Good cheat though, it does work.
If you don't cover with another coat, it'll take a lot more than 1500 to get a mirror gloss finish.
BTW, if someone does too much sanding with your technique, I'd expect it to get a bit smoky - the added poly will cloud with powder removed by the sandpaper. Personally, I'd be tempted to do the sanding with water, clean it up really carefully and then topcoat with a light layer of poly. But I've never done this with wood finishing, so I can't guarantee success. I'd expect a higher quality finish on furniture than on the stuff I've done (boats and such
- but then SWMBO said my weekend's work was fine and I wanted it even glossier).
Yes, this has been more of my (limited) experience. If I even touch the final coat with 1500 sandpaper, it makes the finish clearly more satin than the untouched glossy section.
The wet sanding with some of the finish sounds like a good trick. I've done it with the first coat to fill grain and imperfections, but I never thought about using it for the final coat. I also picked up some auto rubbing compound and polish to try out.
Why I use the 50/50 as lubricant rather than water is that I get the sanding waste into the mix and it becomes a very good "filler" that is part of the gloss. I did vanity top of mahongay a year ago and have used it every day since. It had about 6 coats of poly with sanding to 1500. Ended up with perfect high gloss finish. I wasnt sure how durable a finish would be in active bathroom. At the one year mark, I have no complaints. Wife and I wipe off any water left and occasionally she uses furniture cleaner/polisher. There is a slight loss of high gloss finish over time and it seems to be a surface thing - slight opening of the finish is all I can describe it. Rather than to wait for top to require a major refinish, I put it through 3 days of the 1500 reduces poly/tninner mix and it took very little to get the gloss back, holes filled and another year of "as new", I hope. A lot of what I am going by is vintage methods of hand finishing the Chris Craft wood decks.
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