Polyurethane Dull & Shiny Finish? - Woodworking Talk - Woodworkers Forum
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post #1 of 12 Old 09-21-2017, 11:53 AM Thread Starter
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Question Polyurethane Dull & Shiny Finish?

Greetings,

Just finished my first staining (2 coats) but for some reason, the finish looks shiny/glossy in some areas, and flat in the others. It's been about 72 hours since I last applied the 2nd coat of varnish. I stirred the can well, and purchased a varnish bristle brush to paint it on. Any advice on how to resolve this?

Ovi
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post #2 of 12 Old 09-21-2017, 12:36 PM
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OK, first question. What is the brand and the finish of the poly you are applying? Is it gloss, semi-gloss, satin, or flat? The varnishes (other than gloss) have flattening agents in them and this requires the varnish be constantly stirred DURING application as the agents will settle out to the bottom of the can and leave you with varying levels of gloss. The flatter the finish, the more dulling agents, and the requirement for more stirring. It is also possible that the wood absorbed the finish unevenly and thus the variation. Did you sand between coats with 220, or finer, abrasive?

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post #3 of 12 Old 09-21-2017, 02:15 PM Thread Starter
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Originally Posted by Jim Frye View Post
OK, first question. What is the brand and the finish of the poly you are applying? Is it gloss, semi-gloss, satin, or flat? The varnishes (other than gloss) have flattening agents in them and this requires the varnish be constantly stirred DURING application as the agents will settle out to the bottom of the can and leave you with varying levels of gloss. The flatter the finish, the more dulling agents, and the requirement for more stirring. It is also possible that the wood absorbed the finish unevenly and thus the variation. Did you sand between coats with 220, or finer, abrasive?
Hi Jim,

I used Sherwin Williams Wood Classics Oil Based Stain and their Satin-Clear Polyurethane. I did a light sanding by hand with 220 Grit before I applied the second coat, but I don't really feel I did much with that grit.
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post #4 of 12 Old 09-21-2017, 05:18 PM
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First of all you should never use two coats of stain. With two coats of stain you are likely to let some of it dry on the surface. Then when you put a finish on it the finish adheres to the stain instead of the wood and later peals off. I suspect your shinny places are just that. I think the dull places are where the finish was able to soak into the wood. More coats would cure that but the rest of it is unknown if the finish would stay or not.
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post #5 of 12 Old 09-21-2017, 05:31 PM Thread Starter
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Sorry guys, I meant to say 2 Coats of Polyurethane, not stain. My apologies
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post #6 of 12 Old 09-21-2017, 05:57 PM
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Sorry guys, I meant to say 2 Coats of Polyurethane, not stain. My apologies
OK, the one coat of stain you applied, did you wipe off the excess? If you applied it like paint and let it dry it could cause the same problem. If you did wipe off the excess you are alright, you just have a soft spot in the wood that absorbed the finish instead of building. More coats will fix it. I would be inclined to just add finish on the dull spots until it catches up and then scuff sand it and apply a coat over all of it.
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post #7 of 12 Old 09-21-2017, 06:25 PM
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I always do two coats of stain. I learned that the hard way.

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post #8 of 12 Old 09-21-2017, 07:50 PM Thread Starter
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OK, the one coat of stain you applied, did you wipe off the excess? If you applied it like paint and let it dry it could cause the same problem. If you did wipe off the excess you are alright, you just have a soft spot in the wood that absorbed the finish instead of building. More coats will fix it. I would be inclined to just add finish on the dull spots until it catches up and then scuff sand it and apply a coat over all of it.
Yep, I wiped everything off after 1 minute and worked in sections when I stained it. I'll apply some more Poly to the dull spots until the sheen comes out the same. Should I sand between the coats till it catches up, or just wait for it to catch up? Will 220 or finer do the trick for the sanding? Then just to make sure that I understand, once everything is uniform, do 1 final coat of poly?
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post #9 of 12 Old 09-21-2017, 11:21 PM
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Most of these guys hate Polyurethane, I doubt many of them use it much.


My method is relatively easy, and produces good results.
1# Sand the piece down to 320 Grit, until it's baby but smooth.
2# Blow all dust off with air compresser.
3# Completely wipe the piece down with mineral spirits, and let dry at least 15 minutes.
4# Using a 3" foam brush apply Helmsman Clear Gloss, at full strength.
5# Do not paint the poly on. Use a "New Brush for every coat".
6# Start in the center of the piece, go right to the edge, then go left passing thru you're starting point all the way to the left edge. Look to see that there are no dry spots. If there are repeat the stroke going left first. Slightly overlap each pass, working toward yourself. When you have reach the edge nearest you. Move to the other side of the piece.
7# All of this must be done farely quickly, with no fans or anything that speeds the drying process. The poly must have time to self level.
8# Leave it the hell alone, don't fix anything. "Sometimes the hardest part"
9# After 45 minutes to an hour repeat steps 4 thru 8. Don't worry about ridges or bugs or anything else. The next steps takes care of that.
10# Let dry for at least 6 hours, or up to 24's.
11# Using you're sander go over the whole piece with 320 grit. Do not use any downward pressure. Use you're fingers to test smoothness, you're only trying to level ridges, bubbles, and bug bodies.
12# Blow the white dust off, then wipe down with mineral spirits.
13# Apply the last coat and let dry for 72 hours.


From the looks of the piece in the picture, you should start at #11.

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post #10 of 12 Old 09-21-2017, 11:35 PM
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Quote:
Originally Posted by Ovidio Borrero View Post
Yep, I wiped everything off after 1 minute and worked in sections when I stained it. I'll apply some more Poly to the dull spots until the sheen comes out the same. Should I sand between the coats till it catches up, or just wait for it to catch up? Will 220 or finer do the trick for the sanding? Then just to make sure that I understand, once everything is uniform, do 1 final coat of poly?
Good, it's always a good practice to wipe off the excess stain. With polyurethane the finish needs the scratches created by sanding for it to bond well. Poly isn't known for great adhesion so it can use all the help it can get.
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post #11 of 12 Old 09-22-2017, 02:24 PM Thread Starter
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Thanks for the recommendations everyone. I'll give these a shot and will let you know how it goes.
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post #12 of 12 Old 09-22-2017, 07:04 PM
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Looking @ the photo gives me one more thought...It looks like you may have brushed over areas that had already started to skin. Poly is very sensitive to that.
We don't brush finish. It is harder to produce a nice finish, not that it can't be done just you need a lot more practice to get it professionally done looking.
When we do table tops we use a catalyzed varnish, HVLP sprayed. If you do much finishing it is worth buying a spray outfit. Even the cheap ones can do an OK job, just won't last like the good ones.
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