Help with oil based poly - uneven finish on table after sanding

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  #1  
Old 02-13-18, 12:30 PM
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Help with oil based poly - uneven finish on table after sanding

Help! Our dining table started feeling sticky due to the varnish degrading, and so I decided to refinish the table. It's a wood veneer which is fairly thin. I carefully sanded out the varnish to the wood, restained it, and then applied 3 coats of Oil based poly with a brush, screening with 180 grit in between coats. The last coat was a bit bumpy and with brush marks (of course) and so I started lightly snading with 400 grit to get the table to be smooth. Now, however, I have streaks of shine and streaks of no shine. The shiny parts are _ever-so-slightly_ more raised than the none shiny parts.
  • Do I keep sanding till all the sheen is gone? Wouldn't I be back to where I started?
  • Do I continue with another coat and if so, how to I get the last coat back on smoothly? I've worked with water poly before and had much more luck, this is my first try with oil.
  • Can I make the last coat with water based poly, or do I continue with oil, or do I sand to wood and restart with water based poly (or hire a pro!)?
  • Should I buff it all out with a car wax and a rotary buffer?
  • Maybe I should apply a new coat with the oil based poly thinned with paint thinner to make it easier to apply uniformly? If this is a good idea, should it be like a 50/50 thinning?
Images attached make it seem like the surface variation is wicked bad, but it's fairly smooth to the touch. I can feel ridges between the no-shine and shine areas when I press down with my fingers as a feel across the table.

Thank you in advance. I can't stand looking at what I've done to this table (although it's marginally better than being tacky all the time).
 
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  #2  
Old 02-13-18, 12:36 PM
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Did you use a sanding sealer? Looks like oak and I found using oil poly I got this. I finally used water based poly thinned to about 50%. Got a nice smooth hard finish. Took about 2 to 3 coats put on pretty heavy.
 
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Old 02-13-18, 12:40 PM
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I did not use sanding sealer, I read that they're not really helpful for adhering the first coat, so I just stained and poly-ed. Could I water based-poly on top of this and be ok, or do I need to get back to wood with sanding first? Would the water poly adhere to a screened oil poly finish?
Also is wipe-on poly any good? Should I just stick with the brush on kind? There's also this epoxy you can "pour" right on it, is that a bad idea?
Forgive all the questions, I just don't want to ruin this table, and I know that I don't know a lot.
 
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Old 02-13-18, 12:45 PM
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Could I water based-poly on top of this and be ok
I would be very concerned about adhesion if you did this and, therefore, I would not.

Were the first and second coats better? Sounds like that's what you're saying but that is reverse of what typically happens.
 
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Old 02-13-18, 12:56 PM
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The first and second coats were also bumpy, but I didn't fret about it, I just sanded them smooth after 9-10 hours of dry time using 120-180 grit and applied the next coat. That next coat brought the sheen to an even-ness, but was bumpy due to brush marks and uneven drying after the 10 hours or so. I figured that the final coat I could sand smooth with 400 grit and than buff back to a semi-gloss, but it seems like all the sheen got removed from parts of it entirely.

Understood on adding a new coat with water based poly. Will not do that. Since I know a new coat will even the sheen, I can try a 50/50 split with oil poly and paint thinner for a more even application? Was thinking of using a squeegee or microfiber roller to spread the poly on instead of a brush for that last coat and pray for even application with no bubbles?
Are the spray on polys water based only?
My last resort is to sand the poly off (and hopefully not much wood as the veneer is thin already) and start fresh with water poly.
Sad face.
 
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Old 02-13-18, 01:25 PM
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I find the 50/50 mixture works well for me but only tried a few times with oil based. I always had a problem with smooth till I thinned it.
 
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Old 02-13-18, 02:01 PM
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I tend to apply poly with a rag, would not use a roller based on other's relayed experiences here. Not sure I would start at 50/50 but thinning the poly a bit sounds like a good idea. Additionally, poly shouldn't be over-worked; you want to apply it and be done as opposed to going back over it with the brush again and again.
 
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Old 02-13-18, 02:28 PM
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I hate to wade into this... but here are a few thoughts.

1). Should have used sanding sealer. The whole purpose of using it is that it is easy to sand (unlike poly) so that you can start out with a glass smooth surface. You just need to use one that is compatible with your poly, whether it be water based or oil based.

2). Mixing poly 50:50 is one way guys try to make their own sanding sealer. It is just a thinner coat. But adding the thinner will not necessarily give you a better finish. Thinner will change the evaporation rate of the poly which will affect not only the thickness of the film, but the rate at which it dries and also the resulting gloss. I have see weird patterns in the finish due to the way the thinner flashes first, and the poly later. This is not a big deal if it's your first or 2nd coat, but if it is your final coat, it might not be good.

IMO, if you want to thin your poly to help with the flow, try 10%. But certainly not 50%.

I would put a 220 sanding pad on an orbital sander and sand the bumpy finish on that top until it's flat. Then apply your 10% thinned poly as needed. No reason to start over. And don't over brush it! I know a lot of people apply wiping varnish with a rag. Some like lambswool applicators. (Paint mitts... sometimes used on floors, banisters, or large tables) IMO, you should be using a varnish brush, like this one: https://cloudfront.zoro.com/product/...r-1yicpEx_.JPG

I didn't see where you said what kind of brush you are using, but when applying poly, you don't use any old paint brush.
 

Last edited by XSleeper; 02-13-18 at 02:43 PM.
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Old 02-13-18, 03:01 PM
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I agree with what X said, I'm also partial to the yachtsman brushes although most any decent natural bristle brush will do.
 
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Old 02-13-18, 06:54 PM
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  1. Used a Wooster natural bristle brush, brand name from home depot, one of the more expensive ones, but not the yachtsman. I did certainly overwork the brush, on all coats, thinking it would give me thinner and smoother results. Now I know. I'e tried lambs wool pad before, but it left lots of threads in the finish. I suppose I can weather the pad before using it tho.
  2. Whatcha think of pouring the poly on and spreading it across by pulling a pvc pipe like a t -bar they use for floors? Like a squeegee?
 
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Old 02-14-18, 03:13 AM
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You should be able to get a nice job with a natural bristle brush, try it again without overbrushing. Lambswool pads/rollers do tend to shed a little - that can be reduced by working your fingers thru the pad/cover before it's first use and the issue normally goes away after the first use. I would never roll poly and a pad is over kill for a table top.

Do you remove the dust after sanding?
 
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Old 02-14-18, 06:28 AM
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Yes I wiped down the surface after sending first with dry cloth, then one damp with paint thinner and then dry wipe again.
I should add that I've been doing everthing outside and it's been in the low 50s, would cold make it gum up and be hard to coat smooth?
I'll try thinning and brushing a new top coat today when the sun is up and it's warmer.
once the final coat is dry, do I buff or sand at all? If I should buff it, do I use a furniture wax (or car wax?)
 
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Old 02-14-18, 06:42 AM
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Cool temps will slow down the drying/curing time. It's also possible dust is being blown onto the wet finish. Occasionally when work conditions prevent a decent environment for finishing, if I still have issues after the 4 coat I'll sand with 220 grit and use furniture polish or Johnson's floor wax to finish the job.
 
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Old 02-14-18, 07:11 AM
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I get pretty good results by pouring on and a cheap foam brush. I keep a light where I can see it ant spots did not cover. Do not over work brush.Full coverage is crucial. Look at panel on angle and you will see open spots.
 
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Old 02-14-18, 07:14 AM
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I get pretty good results by pouring on and a cheap foam brush
Do use a foam brush with oil poly or water based? I would have thought that the oil would deteriorate the foam.
 
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