How do you polish the last coat of polyurethane?
Normally urethane does not need a wax. After some use and a good week or two of total cure time, a regular furniture wax like Pledge or Butcher's Wax will help keep the finish clean and shiny. Never use an abrasive polish. If the finish dulls over time, buff it with 220 grit paper and give it a fresh coat of urethane.
Using steel wool or sand paper allows you to create a uniform surface for the next coat of polyurethane, which generally looks nicer, more professionally, etc. In my experience, assuming the finish is dry, there isn't a difference other than the coarseness of the sand paper or steel wool.
Polyurethane doesn't do that so it needs a mechanical method to stick to the previous coat. If you don't sand, the varnish will flake over time particularly if it is a high wear surface. It will also make the surface much smoother.
I always wait a couple days for the poly to cure. When I'm sure the poly is cured I lightly wet sand with 2000 grit to get any dust nubs off, apply wax and hand rub it to a nice sheen. It makes a really nice finish. The cure rate of polyurethane is highly dependent on the environment in which it cures.
Most standard cleaning solutions contain either an alcohol or ammonia base, which over an extended period of time, can eat through the finish. At Grain Designs we also use low sheen urethane finishes. Common furniture cleaners such as Pledge furniture polish, may actually damage the topcoat of your furniture.
The best option is to use a varnish or lacquer to give the wood a high gloss finish. While varnish can be sprayed or brushed on, lacquer is best applied by simple spraying. Spraying makes the surface seem finer than painting as it doesn't leave any strokes behind.
How to Apply Polyurethane: When working with any finish. Use natural bristle for oil-based finishes and synthetic filament (polyester, nylon, or a blend of the two) for water-based and water-based oil-modified finishes. Don't use rollers or foam brushes—they create bubbles.
So, the coats of poly that come from the bottom of the can may contain a higher proportion of anti-gloss additives than the manufacturer intended. If this happens, the sheen may be quite flat looking or may appear dull in patches.
Sanding removes drips, bubbles and other uneven spots in each coat. Dry the first coat for a full 24 hours. If the coat feels tacky or sticky after that, let dry until it feels completely dry. Sand the topcoat with 180 to 220 grit sandpaper.
Coat the entirety of your workpiece, but don't brush excessively or you'll create areas with too little polyurethane. Allow each coat to dry fully. To give the subsequent poly layers something to bond to, sand lightly between coats with 320-grit sandpaper wrapped around a hard block.
Can you wait too long between coats of polyurethane?
It's all about adhesion. When you recoat after 2 hours you get a chemical bond between layers. If you let it go longer than that, you need to wait 24 hours so it's hard enough to sand and get a mechanical bond.
Now, while 3 coats is better, customers can also opt to do an additional coat of poly a year or two later. Now how about more than 3 coats. Generally, more than 3 coats of poly doesn't do much good. It's really not needed nor recommended.
Do I need to sand off old finish completely before applying polyurethane? Generally speaking no, you don't need to completely remove previous finish to apply more of the same finish or a different (compatible) finish1. But there are some caveats.
Steel wool is OK for the final coat but it tends to leave boogers while sandpaper tends to flatten them or knock them loose. I suggest that you use a cork block or a wood block padded with fabric. only sand in between every third or fourth coat. Use 400 or 600 by hand.
Thus, it's best to wait until all coats have been applied and dried before walking through the room. After that final coat, your floors should be off-limits for 24 hours. This is the only way to avoid any damage. Also, if you can swing it, hold off 3-7 days before moving furniture back into the room.
How Long Does It Take For Polyurethane To Dry? After application, oil-based urethanes take about 24 hours to dry, while water-based urethanes require six hours of dry time. However, there's a significant difference between dry time and cure time.
