should you sand the final coat of polyurethane

Do You Need To Sand The Final Coat of Polyurethane?

In Tips by Jamie P.

Refinishing a piece of furniture comes with many questions that you may have a hard time finding an answer to. After you get through the long process you make your way to the final steps, applying the clear coat polyurethane. However, you are now wondering if you need to sand the final coat of polyurethane?

Yes, you can lightly sand the final coat of polyurethane with a 600 grit sandpaper, however, sanding is not required. Sanding can potentially leave a cloudy or scuffed looking surface to your polyurethane finish.

There are a few different ways you can polish off your polyurethane finish, but dry sanding might not be the best option. Let’s look at how we can create a final smooth touch to our poly projects.

How Do You Smooth the Final Coat of Polyurethane?

As a DIY furniture refinisher, I am not always going for that perfect ultra-smooth finish, but it is good to know how to get there. Refinishing dining tables and bookshelves, it’s nice to get as smooth as possible with your final coat of polyurethane. Here I will go over various methods that can be used individually or combined for great final results.

Dry Sanding The Final Coat of Polyurethane Finish

Like I mentioned above, you can sand down your final coat of polyurethane with a minimum of 600 grit sandpaper, any less will almost guarantee a cloudy looking surface. Realistically, dry sanding polyurethane at any grit can potentially leave a scuffed looking cloudy surface.

If you plan to dry sand as a final touch, just do a quick wipe without applying too much pressure. This will lightly sand the surface removing dust particles while reducing the cloudy-looking finish.

If you do this process, I recommend implementing the wax buffing process I mention below. This will hide any scuffs in the finish from dry sanding. So if you already did this and thought you ruined your piece, just buff it out!

Wet Sanding The Final Coat of Polyurethane Finish

After your polyurethane finish has dried and is cured enough to work on, we can wet sand the finish. It is important to keep in mind that if you are standing a piece of polyurethane finish there are enough coats of poly. 1-2 coats risks sanding through to the wood, apply 4-5 coats to be safe.

Wet sanding is pretty simple, here’s what to do:

  1. Pour mineral spirits over the poly finish
  2. Use a minimum 400 grit sandpaper wrapped around a sanding sponge
  3. Lightly begin wet sanding in the direction of the grain
  4. Let the mineral spirits evaporate

Now the finish is smooth and because you chose to wet sand you shouldn’t see any cloudy-looking surface scuffs. Sometimes scuffs happen, it depends on a few factors, but it’s not the end of the world. Following the buffing methods of using wax and steel wool, I mention below can fix up those final flaws. Or applying another coat of polyurethane will hide such sanding scuffs.

Not Touching The Final Coat of Polyurethane

When working on a schedule and time isn’t your best friend you can just leave your final coat of polyurethane without doing any sanding. Honestly, in many of my projects where I apply a clear coat finish, I will sand between coats but not the final one.

If I get that scuffed surface, I need to apply another coat or buff with finishing wax paste. This is a time sucker. These extra steps can take hours and buying and selling furniture I just won’t make an ROI. Plus, most people don’t even notice the surface isn’t glass smooth. But hey, I know if you are a woodworking pro or have your own business going you are pretty keen to get that ultra-smooth touch. So spend that little extra work and get the finish you want.

Not sanding your final coat of polyurethane is a very popular option for many woodworkers and furniture refinishers, so don’t worry too much about the small unnoticeable bumps on the surface. If anything, try to mitigate these issues by wearing clean clothes during the polyurethane coats, dirty clothes can cause dust particles to lay on or mix in the poly causing those little bumps.

Buffing Your Polyurethane To A Smooth Finish

Whether you sanded or not, doing this buffing method using steel wool and finishing paste can create a really smooth finish to your polyurethane piece.

Here is what you do:

  1. Use 0000 fine steel wool and dip it in your finishing paste wax.
  2. Take your wax-dipped steel wool and rub it back and forth in the wood grain direction on the polyurethane finish.
  3. Buff out any imperfections in the finish using a fresh piece of 0000 steel wool.

Yes, it’s that simple. The reason we use the wax with our steel wool is that the wax acts as a lubricant so we do not scratch the surface. The best wax to use is Minwax Paste Finishing Wax in a natural color. The buffing motion with the steel wool will remove any dust particles that may have reached the surface of the polyurethane before it had dried.

Buffing to this degree is recommend for busy surfaces that need that durable surface. This means tabletops, end tables, nightstands, and coffee tables. Places that aren’t used frequently you can probably skip and just let it be to save you some time. But hey, that’s up to you my friend.

What Happens if You Don’t Sand Between Coats of Polyurethane?

If you do not sand between coats of polyurethane, you risk dust particles causing minor imperfections in your finish. Although sanding between coats is not required it is highly recommended for creating maximum smoothness.

Is One Coat of Polyurethane Enough if Sanding?

No, one coat of polyurethane is not enough to create a durable clear coat finish. It is recommended to apply at least 3 coats of polyurethane to your wood projects.

Since we talk about sanding a piece of polyurethane, if you sand the final coat and you applied one coat of poly, you could quickly go through to the bare wood. This will cause your wood project to quickly become damaged from traffic or water. Seal your poly projects with at least 3 coats at minimum.

Final Thoughts

Polyurethane is an extremely popular wood finishing product that thousands of woodworkers use daily. Sanding it for a smooth finish is possible, but remember the other methods that are available. Maybe no sanding can work for you too! Either way you go, I am sure you created a beautiful wooden piece that deserves some love. Good luck with finishing your project!