Apply only one thin coat. Then, remove any dust nibs with 1,500-grit sandpaper or a piece of brown paper bag. Finally, using a soft cotton rag or polishing pad, buff the finish to a high shine using automotive paste wax, photo below, which has fine abrasives that polish the finish even further.
To fix it grab a hard block with some 220 and do a directional sand until you get the surface even. And be very careful as you approach the edges, as there tendency to thin them more than the surrounding surface. Then clean with compressed air and a damp rag (mineral spirits). Apply another coat with thinned out poly.
If your existing urethane finish needs extra protection but not a total refinishing, you can re-coat it with Minwax® Helmsman® Spar Urethane, provided you follow the three rules for re-coating: clean, dry and scuff. First, clean off any wax and dirt with a cloth dipped in mineral spirits.
Make sure to sand the polyurethane between coats.
You can rub out all types of film forming finishes, including shellac, lacquer, oil based varnish and polyurethane, waterbased coatings and catalyzed or conversion coatings.
“The most common causes for bubbles are shaking the can and improper brush prep—you don't stick a brush into the finish without first soaking the bristles in mineral spirits, for oil-based polys, or in water, for water-based polys.
Buff the polish into the finished project until the surface looks shiny. Turn your orbital sander onto a low speed and apply a small amount of pressure to the finished surface. Work in long, horizontal motions to work the polish into the polyurethane. Don't be discouraged if the surface doesn't look shiny right away.
First, wet sand with low grit sandpaper that can be used both wet and dry. Then apply rubbing compound to the coat. Next, wipe away excess clear glaze with a microfiber cloth. This process gets rid of any imperfections and makes the coat look new again.
Bubbles and streaks can ruin the smooth finish of your polyurethane floor. To avoid bubbles, make sure to stir the polyurethane gently and avoid shaking the can. When applying, use a high-quality brush or roller and apply thin, even coats.
In short, that rough texture that you feel is basically a mix of micro-level dirt that has stuck to your clear coat that won't come off with a simple wash. It can be things like industrial fallout, paint overspray, metal shavings, dust, etc…
If you are getting a rough finish after several coats of varnish, you may want to wet-sand the surface with 220 grit to level it out. Here I have leveled out the finish prior to the final coat and sanded it to 320 grit. I vacuumed the surface, wiped it down with a ragged wetted with mineral spirits.
Pour the acetone onto the surface or apply it with a brush. Wait 10 to 15 minutes for the acetone to soften the polyurethane. If necessary, scrape the polyurethane away with a putty knife or scraper. Wipe the surface clean with a dry cloth.
Use a damp rag or sealant tool to smooth the bead of sealant and seal the seam. Clean up immediately with a damp rag.
Waterborne polyurethanes usually require a minimum of 3-4 coats to be effective. Although there is some evidence that too many coats can result in a plastic-like finish, waterborne polyesters are thinner than other types and therefore require several more coats to provide the same protection for hardwood floors.
Paint Bubbling on Car Hood & Panels
As the moisture is painted over, air is then trapped within and will form bubbles underneath the paint. Over time these tiny bubbles will come up to the surface and cause the paint to chip off. To repair this problem the only answer is to refinish the panel.
There is no difference between the terms urethane and polyurethane. That might seem confusing, so here's a quick explanation. Polyurethane is a polymer. A polymer consists of repeating units that are chemically linked in a particular pattern.
Pop and Smooth: If you see bubbles forming, gently pop them with a pin or sharp blade while the finish is still wet. Then, smooth the area with your brush or applicator. Let It Settle: Give the polyurethane a few minutes to settle after stirring but before applying it.
You should use an automotive polishing compound and a buffer for big areas. Small areas will have to be polished by hand unless you have some funky buffing tools. Make sure the poly has cured for a minimum of 4-5 days at 70f. Do not try to polish an uncured film.
Minwax Wipe-On Poly is a high quality, durable polyurethane finish that provides protection with a classic, hand-rubbed look. It delivers a hard, clear finish that protects wood against water, household chemicals, food stains, and wear. Wipe-On Poly is easy to apply.