Trouble with gloss polyurethane - Woodworking Talk - Woodworkers Forum
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post #1 of 13 Old 04-21-2018, 11:18 PM Thread Starter
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Trouble with gloss polyurethane

Pretty new to wood working, despite this I'm still getting pretty good results.

Not with high gloss polyurethane though.

My clear satin finishes have been turning out pretty well.

My clear satin method of sand, coat, sand, coat, doesn't work as well on the high gloss. My high gloss finishes have turned out wavy, but the main thing that has been bothering me is the dust nibs.

So I took to the internet and videos to try to figure out what I'm doing wrong. I have tried a wet sand, I have tried buffing with a Polishing Compound, and polishing with an orbital sander. I'm just not getting good results. I'll attach a pic here of a small test project made from scrap pieces left over.
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post #2 of 13 Old 04-22-2018, 05:46 AM
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Try adding some reducer/retarder to your gloss poly to get it to flow out better. That should help with less waves. Or spray it.

To polish, wet sand with 600 grit up to 1500 grit. You'll need to have a few coats of build up before you can polish. With the 600 grit work the surface until all the highs and lows are gone and you have one consistent sheen across the entire surface. Then work your way through the grits. Lastly, polish with supercut compound and do a final hit of swirl remover. You'll have a shiny finish that will be free of nibs and real clear.
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post #3 of 13 Old 04-22-2018, 07:50 AM
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The poly should self level but will have a problem doing so if the work area temperature is too cool. What are you using to apply the poly? You could be over brushing......use a light touch. Are you cleaning the surface of sanding debris or is there airborne dust. You don't want too much air movement while the poly is drying. Also, you may have contaminated the poly in the can with sanding dust.
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post #4 of 13 Old 04-22-2018, 08:31 AM
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Quote:
Originally Posted by BobVila View Post
Pretty new to wood working, despite this I'm still getting pretty good results.

Not with high gloss polyurethane though.

My clear satin finishes have been turning out pretty well.

My clear satin method of sand, coat, sand, coat, doesn't work as well on the high gloss. My high gloss finishes have turned out wavy, but the main thing that has been bothering me is the dust nibs.

So I took to the internet and videos to try to figure out what I'm doing wrong. I have tried a wet sand, I have tried buffing with a Polishing Compound, and polishing with an orbital sander. I'm just not getting good results. I'll attach a pic here of a small test project made from scrap pieces left over.
From the picture it appears you have about twice as much poly on there as needed. In order to restore that part it would be easier to strip it and start over. Poly sands hard and it would take a lot of sanding to level it. I suppose you could try sanding it with an orbital sander with 180 grit paper and remove most of it. When you get real close you might switch to 220 grit. Once level you could apply another coat and see what that does for you.

A gloss finish is going to show any and every defect in the finish. For this reason I would recommend getting a sprayer and spray the finish. This would eliminate most of the problems you are having. Still you have to be very clean when working with any finish. Most of the time when a painter gets dust in a finish the dust is falling off the painters clothes. If you do a lot of sanding, especially on wood you get the dust on yourself and then falls in the finish.

If you are going to brush the finish use as soft a brush as you can find and apply the finish as thin as you can with as few strokes as possible. The more you brush a finish the more texture and brush marks will show. Brushing the finish gets more air in the finish and can cause it to set up prematurely. The brush more or less makes grooves in the finish and if you apply it and get off of it the finish will be wet enough to flow back together and level before it sets up. If you continue to have difficulty brushing a finish before it sets up you might add some Flood Penetrol to the poly. This slows down the drying time of the finish.

For gloss though you can't eliminate the brush marks 100%. Doing a gloss with a brush after you have enough finish applied you wet sand it with 1200 grit sandpaper with a hard rubber sanding block until you level the finish. Then you progressively wet sand up to 2000 grit paper. From there you bring the sheen back by buffing the finish with an auto polisher with a lambswool bonnet and rubbing compound. It's a lot of work which could be eliminated with a twenty dollar harbor freight sprayer.
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post #5 of 13 Old 04-22-2018, 10:10 AM
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Foam rubber brushes work well. Get good ones......not the ones that are 10 for $1.00.
Poly should be applied in very thin coats.
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post #6 of 13 Old 04-22-2018, 11:25 AM Thread Starter
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Originally Posted by J_L View Post
Try adding some reducer/retarder to your gloss poly to get it to flow out better. That should help with less waves. Or spray it.

To polish, wet sand with 600 grit up to 1500 grit. You'll need to have a few coats of build up before you can polish. With the 600 grit work the surface until all the highs and lows are gone and you have one consistent sheen across the entire surface. Then work your way through the grits. Lastly, polish with supercut compound and do a final hit of swirl remover. You'll have a shiny finish that will be free of nibs and real clear.
I will try this method. It sounds very similar to the steps I tried with the automotive polish. When I use that method, the gloss looks scuffed or cloudy (For lack of better description) no matter how much I polish.

Is supercut compound significantly different than the auto polish? And do you have brands you recommend for the supercut compound & swirl remover?
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post #7 of 13 Old 04-22-2018, 11:30 AM Thread Starter
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Quote:
Originally Posted by JIMMIEM View Post
The poly should self level but will have a problem doing so if the work area temperature is too cool. What are you using to apply the poly? You could be over brushing......use a light touch. Are you cleaning the surface of sanding debris or is there airborne dust. You don't want too much air movement while the poly is drying. Also, you may have contaminated the poly in the can with sanding dust.
I have tried a foam brush, bristle brush, rags, and paper towels.

I clean the surface well (I think). I've tried vacuuming the dust up, wiping it, covering the project while it dries, wetting surroundings with a spray bottle, and trying it in a different room.

Finally I broke down and decided to post, lol.
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post #8 of 13 Old 04-22-2018, 11:38 AM Thread Starter
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Originally Posted by Steve Neul View Post
From the picture it appears you have about twice as much poly on there as needed. In order to restore that part it would be easier to strip it and start over. Poly sands hard and it would take a lot of sanding to level it. I suppose you could try sanding it with an orbital sander with 180 grit paper and remove most of it. When you get real close you might switch to 220 grit. Once level you could apply another coat and see what that does for you.

A gloss finish is going to show any and every defect in the finish. For this reason I would recommend getting a sprayer and spray the finish. This would eliminate most of the problems you are having. Still you have to be very clean when working with any finish. Most of the time when a painter gets dust in a finish the dust is falling off the painters clothes. If you do a lot of sanding, especially on wood you get the dust on yourself and then falls in the finish.

If you are going to brush the finish use as soft a brush as you can find and apply the finish as thin as you can with as few strokes as possible. The more you brush a finish the more texture and brush marks will show. Brushing the finish gets more air in the finish and can cause it to set up prematurely. The brush more or less makes grooves in the finish and if you apply it and get off of it the finish will be wet enough to flow back together and level before it sets up. If you continue to have difficulty brushing a finish before it sets up you might add some Flood Penetrol to the poly. This slows down the drying time of the finish.

For gloss though you can't eliminate the brush marks 100%. Doing a gloss with a brush after you have enough finish applied you wet sand it with 1200 grit sandpaper with a hard rubber sanding block until you level the finish. Then you progressively wet sand up to 2000 grit paper. From there you bring the sheen back by buffing the finish with an auto polisher with a lambswool bonnet and rubbing compound. It's a lot of work which could be eliminated with a twenty dollar harbor freight sprayer.
Yea, I know what you mean about the amount of poly on it, but I have tried more conservative amounts.

And thanks for the method tips. Any tips for someone who has tried this method but was unable to yield good results on the last polish? Seems no matter how much I polish it has a cloudy look to it.
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post #9 of 13 Old 04-22-2018, 11:40 AM
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Quote:
Originally Posted by BobVila View Post
I will try this method. It sounds very similar to the steps I tried with the automotive polish. When I use that method, the gloss looks scuffed or cloudy (For lack of better description) no matter how much I polish.

Is supercut compound significantly different than the auto polish? And do you have brands you recommend for the supercut compound & swirl remover?
Presta makes both the supercut and swirl remover. Not inexpensive but they work very well and yes, supercut is different from auto polish. Supercut is much more aggressive than typical auto polish. The swirl remover would be more comparable to the auto polish which is utilized after supercut has done the brunt of the work. As Steve mentioned above, hit it with a buffer with a lambswool pad. Use different pads for the compound and swirl remover.

Cloudiness means there is still work to be done. As you work your way up through the grits, you'll notice that somewhere around 1200 grit and up that there is a slight shine with some cloudiness. The supercut compound takes that cloudiness away and polishes it out to a gloss finish. The swirl remover is the icing on the cake.
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post #10 of 13 Old 04-22-2018, 11:45 AM Thread Starter
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Originally Posted by JIMMIEM View Post
Foam rubber brushes work well. Get good ones......not the ones that are 10 for $1.00.
Poly should be applied in very thin coats.
Thank you. Yea, I'm a fan of thin coats. The only exception to this is my tung oil finish. I do multiple thin coats with wet sands, then the last coat can be caked on.
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post #11 of 13 Old 04-22-2018, 12:53 PM
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Yea, I know what you mean about the amount of poly on it, but I have tried more conservative amounts.

And thanks for the method tips. Any tips for someone who has tried this method but was unable to yield good results on the last polish? Seems no matter how much I polish it has a cloudy look to it.
If you took a piece of plexiglass and sanded it with very fine sandpaper it wouldn't matter what kind of polish you used and how you did it. The scratches would have to be polished out first. It's the same with a finish. It's very difficult to get there if the finish has been sanded with anything coarser than 1200 grit paper. It would be worth sanding out the nibs and applying another coat before doing that. Like I outlined on the above post you progressively wet sand with finer and finer paper until you get to 2000 grit and then it would have to be buffed using an electric polisher and rubbing compound. By the time it's buffed the finish should look clear and shiny. Polish is only used to get the residue of the compound off.

I use this buffer when polishing a finish in that manor. https://www.harborfreight.com/7-in-1...her-62861.html
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post #12 of 13 Old 04-22-2018, 01:54 PM
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Turtle wax makes polishing compound that is finer grit then rubbing compound, but cheap tooth paste will also really polish the finish. Back when I had airplanes I used tooth paste to polish the windshields they were plastic, and at times would get slightly hazy, and sun or runway lights would really show the haziness, tooth paste and elbow grease would make them super shiny again

But the Turtle Wax Polishing compound doesn't leave the mint scent ot toothpaste LOL
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post #13 of 13 Old 04-22-2018, 03:09 PM Thread Starter
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Originally Posted by J_L View Post
Presta makes both the supercut and swirl remover. Not inexpensive but they work very well and yes, supercut is different from auto polish. Supercut is much more aggressive than typical auto polish. The swirl remover would be more comparable to the auto polish which is utilized after supercut has done the brunt of the work. As Steve mentioned above, hit it with a buffer with a lambswool pad. Use different pads for the compound and swirl remover.

Cloudiness means there is still work to be done. As you work your way up through the grits, you'll notice that somewhere around 1200 grit and up that there is a slight shine with some cloudiness. The supercut compound takes that cloudiness away and polishes it out to a gloss finish. The swirl remover is the icing on the cake.
Ok, I'll get those. By cloudiness I mean no matter how long I buff. However I haven't tried those products, I'll grab them and a lambswool pad. Thanks.
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