Sign In to join the community | Help

Best way to get a smooth finish with polyurethane

Hello everyone. There seems to be a lot of controversy on a rough first coat of polyurethane and what to do about it. After 40 plus years of finishing doors, woodwork, furniture etc I can tell you what I use and it's easy and comes out baby butt smooth. After you have done your prep work on light sanding your piece, and applying how ever many coats of stain that you wish, I usually stain with flour sack towels, cheap and lint free. I cut them to about 8x8. After stain is applied I do a close look. I then take a hair dryer and blow off any specs of dust or anything that may be there. I then apply a first coat of polyurethane with a natural hair paint brush ( cheap about a dollar a piece and can toss away, usually have a wooden handle). After it is completely dry usually overnight, depending on humidy, (and don't rush this step. It must be completely dry) then I take a sanding block usually about 4" and put 2000 grit. Yes 2000 grit not 200 grit sandpaper in it and get a bowl of water. Dip your sanding block in the water and wet sand in the direction of the grain. Not to hard to remove the polyurethane, you just want to remove the bumps. As you start to see a slight white liquid wipe it as you go. When you are done sanding wipe off all water. Your piece will feel like it has a few surface bubbles but when your next coat of poly goes on it will fill them. What you are feeling is the tiny holes from the bubble tops you just sanded off. Before you apply your 2nd coat of poly take hair dryer again and blow off your piece for any minuscule stuff you may see. Brush poly in direction of grain. Go back and smooth out after a couple of minutes with same brush. When this is totally dry it will be as smooth as glass. Easy. Simple and cheap. Thanks for listening and good luck
Not what you were looking for ? Try posting a question
Posted 2016-01-02T00:12:19+0000  by LittleBit58 LittleBit58

Hi LittleBit58,

Thanks for joining us on the community and giving us this great information!

All I wanted to add that when working with polyurethane, 2000 grit is sold at most local Home Depot's....but it is available only in the type shown below and linked here.

3M 3.66 in. x 9 in. 2000 Grit Sandpaper (10 Sheets-Pack)

I only mention this because this sandpaper typically goes on sanding blocks, which can be cumbersome for detailed poly projects, like clear coating a chair with slats, as an example.

And as an added alternative to some furniture and cabinet projects, lacquer is a great choice in that regard. Less work is required versus polyurethane and can give you great results too.

Thanks again for those handy dandy tips LittleBit58, and keep them coming!



Posted 2016-01-02T15:55:43+0000  by Joseph_HD_ATL

Getting super fine finishes is why Sanding Sealer was invented. Sanding sealers help fill open grain woods and "set" the grain that usually raises a little after the first coat of varnish or sealer. Sanding sealers are very easy to sand with a fine white dust resulting. Normally, a 320 or 400 grit sandpaper works fine, however, care should be taken not to sand through sharp corner edges, exposing bare wood!

There are dedicated polyurethane sealers. Traditional sterate based sealers are not compatible with urethanes, nor is regular shellac.  A "de-waxed" shellac , otherwise known as "universal sealer" is compatible with urethanes. Zinsser's "Seal Coat" is such a universal shellac based sealer.

Behr does make a water based universal sealer, over which urethanes may be placed.

Oil based stains themselves also act to "set" the grain of bare wood

The general order of wood finishing is as follows:

1.  Sand bare wood smooth and dust clean
2.   Stain.  A Pre-Stain Conditioner may be necessary on some woods, generally soft woods. Let dry.
3.   Apply Sanding Sealer.  Let dry.  Sand with fine 320 or 400 grit sandpaper, then dust clean.
4.   Apply multiple coats of Polyurethane. Two coats is advisable, another if it is a high use area. Follow the 
      manufacturer's  instructions as to re-coat times. 

The gloss is largely per personal taste. However, if you want the piece to look like the wood case of a 1950's Grundig radio, wet sand the last coat of gloss urethane with that 2000 grit paper mentioned by the original poster. Don't use a sanding block, as most woods are not a flat as you think the are. A sanding block will "scalp" the high spots and miss the low spots. A hand held folded piece of sandpaper will conform to the surface.

Posted 2016-01-03T08:24:29+0000  by ordjen
Hey LittleBit58,

Great overview!

Your topic is discussed in step-by-step detail in an earlier thread:

How To Produce An "Old School" Glass-Like Polyurethane Finish

The ultimate "How To" when it comes to professional clear coats.
Posted 2016-01-05T21:08:38+0000  by Pat_HD_ATL
Not what you were looking for ? Try posting a question