Polyurethane finish

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Old 10-05-18, 02:13 PM
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Polyurethane finish

Can I buff out polyurethane imperfections with 3m pad and orbital sander?
 
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Old 10-05-18, 03:19 PM
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How long has the poly cured? It can be buffed a little but not aggressively.
 
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Old 10-05-18, 03:20 PM
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Polyurethane should get a light sanding with 220 grit between every single coat. What kind of imperfections are you talking about ?
 
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Old 10-05-18, 03:40 PM
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It has been like 6 hours since last coat.It looks like too much poly in a couple spots and when it dried looks like a circle.
 
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Old 10-05-18, 03:51 PM
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Circles in a finish are often called "fisheye" where the finish simply won't cover and it migrates away from an imperfection. It's often caused by poor preparation of the surface... oils or waxes or silicones that were not removed prior to applying the poly.

If we knew more about the project we might be able to give better advice. But in my experience with a fisheye there is a sizable ridge of finish built up around the edges or the fisheye, like a mini-volcano. I have had some success carefully scraping that ridge with a razor blade on edge... dragging it almost perpendicular to the surface to scrape off the hump. Followed by aggressive hand sanding with 220 on a sanding block (a perfectly flat block helps identify the high points... and ur less likely to sand down through the finish to bare wood). Wipe with paint thinner and let dry before applying another coat of poly.

But no... I would not use an orbital on it... probably not even with 220 grit paper. You can pretty quickly ruin a project faster than you can turn it off.

If you have pictures, post them.
 
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Old 10-05-18, 04:00 PM
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I didnt mean to use sandpaper with orbital sander. I seen a YouTube video where they use a 3m pad with orbital sander. I
 
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Old 10-05-18, 04:09 PM
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You don't want to polish it... you need to remove (flatten) the hump. You can't spread poly once it's dry... it's not a wax.
 
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Old 10-05-18, 04:12 PM
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Ok. I'm no professional. Just want to fix without having to sand and polyurethane again.
 
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Old 10-05-18, 04:15 PM
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Yes well I'd like a million dollars without having to work for it but that's probably not going to happen either. LOL! Go ahead and try and let us know how it works out for ya. Sometimes you never know until you try. Maybe it will work, maybe it won't. Other times you wish you hadn't tried... and would have listened to dad... or grandpa... or some guy on the internet.
 
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Old 10-05-18, 04:25 PM
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That's why I'm on here. Idk if I should sand again or not.
 
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Old 10-05-18, 04:27 PM
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If it was me, I would try what I mentioned in post #5. But I can't make you. LOL.
 
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Old 10-05-18, 04:54 PM
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Does this mean polyurethane the entire table?
 
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Old 10-05-18, 05:49 PM
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Yes, otherwise you will see the lap mark where you stopped and started. If you don't mind seeing that slight sheen change, then do what you like.
 
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Old 10-05-18, 06:15 PM
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What about wipe on poly? Is that as good? It would be easier.what kind of cloth do you use?
 
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Old 10-06-18, 03:22 AM
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As noted above fisheyes are caused by a contaminate on the substrate. They sell fisheye medicine you can add to automotive paint [before you get fisheyes] but have never heard of anyone using it with any other type paint. The only way I know to remove fisheyes is to sand them out. When sanding is done you should always take a clean rag damp with thinner and wipe the surface down removing the sanding dust along with any other contaminates. The rag should be turned over or replaced as needed.

Assuming this is just the top - all you'd need to sand and recoat would be just the top. While a piece may not need to be redone entirely - you need to do whole sections. Poly does not touch up well!
 
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Old 10-06-18, 03:26 AM
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Okay but was just wondering about wipe on poly. Is that as good? It would be easier.what kind of cloth do you use?
 
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Old 10-06-18, 03:30 AM
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Many get good results with wipe on poly but I've always shied away from it because I doubt you could apply enough mil thickness to get lasting results. You'd want to use a white lint free cloth. An old T shirt should work well.
 
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Old 10-06-18, 05:40 AM
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They sell fisheye medicine you can add to automotive paint
I have never seen fisheyes in a project like this so something is wrong, it wasn't sanded properly, it wasn't cleaned properly and using the fisheye remover is a band aid, not the cure.

IMO you probably need to take it all off and start over, let me guess, some big box store brand of stain and urethane, it's all krap and causes issues!
 
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Old 10-06-18, 06:04 AM
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Well if I sand this one more time before putting poly on is 220 too rough to use for last coat or should I do something different. It always seems light it takes alot of previous poly finish off.what If there is spots where there is poly and spots where there isnt as much?
 

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Old 10-06-18, 06:54 AM
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Normally any sanding scratches put in the previous coat of poly are filled in with the next coat of poly. I've never seen a need to sand any painted or poly'd wood with any grit finer than 220. It is important to sand with the direction of the grain and not across the grain.
 
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Old 10-06-18, 06:57 AM
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Thank You. I will try again.😊
 
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