Polishing Polyurethane to a High Gloss

      Buffing compounds, sanding materials, and techniques for that super-high final shine. May 24, 2006

Question
I have been doing a few projects lately with high-gloss polyurethane finishes. The final coats keep having minor bubble spots and/or lint/dust spots. I have been doing it in a fairly dust free room to avoid most of the dust spots, but I still get a few. And I have been thinning my polyurethane, but I still get a few bubbles. I am assuming that they are hard to avoid entirely. So, my final coat is not mirror smooth. There are always some little imperfections and spots. I am primarily doing this on decent sized flat surfaces, 5-6 sq/ft. So, the spots are too noticeable for this type of project. How do you polish these few imperfections out of polyurethane after the final coating to still maintain a high-gloss, smooth finish? I have tried 2000 grit paper and 0000 steel wool. They are both way too abrasive, and dull the finish a lot. Also, do any of you use wax on top of your final finish?

Forum Responses
(Finishing Forum)
From contributor A:
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. Start gently, sand all the imperfections (wet 1000g) and then clean the surface well. Use a fine cut cleaner by McGuire's or 3M and follow the instructions on the bottle. Clean all residue when done with a damp cloth. Repeat the polish process with a swirl mark remover. Again, clean all residue with a damp cloth and buff clean with a cotton cloth.

Apply a final polish of your choice. This should give you a table that is like a mirror. Also, try this out on a test panel first to make sure you like the result.



From contributor S:
Get a hold of Mirka Abrasives Abrenet/Abralon system and watch that labor of love poly shine...


From contributor A:
Contributor S is right about the Abralon pads - they work really good and let you buff out a wide range of sheens quickly and easily. I can't seem to get them here where I am, though. Maybe I'll get a bunch on my next shipment. You can also do it the way I mentioned, a bit more work but looks pretty darned good. There are also other polish systems out there that work even better.


From the original questioner:
Thanks for all of the replies. However, now I am a little confused. It appears some of the Meguires products are used in the wood finishing industry. I get the impression that some people are pretty happy with their results using Meguires products on wood finishes. I have not figured out which ones to use in which order yet.

Then there is the Mirka Abranet/Abralon series of abrasives. I went to their website and saw that the Abranet series abrasives are mesh and go up to 2000 grit. The Abralon series is foam backed and go up to 4000 grit (nothing between 2000 and 4000). I don't have a vacuum system hooked up to my sander, so I don't think the Abranet abrasives buy me much. I assume the Abralon would be the way to go if going with Mirka. However, I have been using 3M wet paper up to 2000 grit. 2000 grit still leaves the finish very hazy. 3M 2000 grit and Mirka Abralon 2000 and 4000 are all silicon carbide. Other than the foam backing on the Abralon, what is the difference? Will the Mirka 4000 grit be that much better? Or am I better off going up to 2000 with the 3M wet paper (4000 Abralon if I can find it), then following with Meguires type products? I have never seen Mirka products around. Where do you get them (I am near North Houston)? I do have a polisher. If I go up to 2000 grit (or 4000 if I can find it) and then I go with Meguires (or comparable 3M polishes), does anyone have a recommendation for which particular Meguires products (or 3M) to use? And in what order?



From contributor A:
New fancy pads and stuff get a little complex. Generally, I use the following.
Rub lightly 0000 steel wool (synthetic)
Cut wax with with McGuiar's #2 Fine Cut Cleaner
Polish with McGuiar's #9 Swirl Mark Remover
Polish again with any of the final polishes

For more information on the Abralon Pads, check out TargetCoatings.com.



From contributor D:
Mequires is good. But their products are too mild. And they are made to break down as you use them because they want to help you to avoid rub-throughs. I avoid rub-throughs by having years of polishing experience, not by a product designed to hold my hand and stymie me. That said, use 3M's Microfinishing Compound and finish that up with 3M's Finesse-It II (that's "two"). You can use either a lambswool polishing bonnet or the foam pads. I like both. I can get closer to edges and not have them burn through with the foam pads. Being foam, they break down with use and time.

To avoid dust, are you wearing a Tyvek suit? Makes a lot of difference. In a spray booth that has lots of air flow, you would be surprised how much lint and dust the fan pulls off of you. Also, wet the floor down before you spray.

Sanding grits (wet dry): 500, 800, 1200, 1500. Then go to the polishing compounds. You will end up with a piano-like shine.



The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor T:
I recently completed a kitchen table project for my own family. We have three very active kids who can destroy pretty much anything you put in front of them. For the table finish, I chose a product called Ceramithane that I had used in the past on their nursery furniture. It has held up well because it is essentially a water-based gym floor finish that can be sprayed. However, it does tend to orange peel a bit and therefore required wet-sanding and polishing for my kitchen table project.

I sprayed on four coats with a light scuffing in between with 400-grit dry paper. After the final coat had cured for a couple of days, I started the wet sand process. I found a local auto body shop supplier with a good selection of 3M wet/dry papers. Using a stiff foam block purchased from the same store as the papers, I began with 1000-grit, liberally spraying the surface with water containing a little bit of dish soap (I used Dawn and it worked fine).

This first grit is the most critical as it flattens the orange peel and gets out the major imperfections. You have to let it dry completely before you can really see what you've got. You're looking for a uniform dull finish. Any areas that show up still shiny mean you haven't knocked them down enough and the finer grits will never touch them. Once you're sure you've got a good 1000-grit base to work from, proceed through 1200, 1500, 2000, and 2500 grits.

Keep the paper wet at all times - you're looking for a kind of milky "slurry" indicating material is both being removed and being carried out from under the paper. If your paper gums up with little globs of material, toss it and get another sheet. I found rubbing with the grain was fine, no need to make circles or figure eights. After finishing the 2000 grit pass, rinse off and let dry. The final step is to buff out the 2000-grit scratches with polishing compound. I used 3M "Perfect-It" and my Porter-Cable worm drive random orbit sander.

Both the rubbing compound and the foam pad that velcro’s to my sander came from the auto body supply store. Dribble some compound onto the surface and start up the sander. It's messy, so count on compound slinging around the area. Polish until the compound dries up, then wipe off any excess. You should see a near-mirror finish. Mine came out better than anything I've ever finished before in fifteen years of what I'll call serious hobbyist woodworking. It was much better than any sprayed or brushed finish. The only thing that might be better is a good French polish, but I personally don't have the time or patience for that. Good luck and one last piece of advice: practice on a test piece to get a feel for the papers - 1000-grit doesn't sound very aggressive, but it will eat your lunch if you don't know when to stop.



Comment from contributor E:
To avoid bubbles and dust in finish, I pour in a dust free room with a small portable blow torch at hand and if bubbles pop up I take care of them then. Cover the project with dust free box and/or set up a small car port type cover with poles after you are sure all bubbles are out. The cover/s will keep any falling dust from getting on the finish.


Comment from contributor L:
To get optimum results you need to sand back the lacquered surface. A Mirka Polarshine 1500g disc on an orbital sander will work well. Then use a Lamb’s Wool bonnet and apply a small amount of C20 cream, damp with a little water. Wipe clean and then apply T10 cream (also Mirka) on an orange dotted pad on a polisher at around 2000rpm with light pressure. You will get a mirror finish no problem. If you want to you can finish off with F05 cream on a flat black sponge head.



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