Issues sanding Polyurathethane


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In a bit of a pickle due to my inexperience.  I put on my first coat of Minwax fast drying polyurathane today, and I had some dust and dog hair fall on to my project.  I figured during the sanding phase all would be well.  I used a orbital sander with 220grit, and now I have these white sanding marks from the sander.  Is this going to be an issue? I've read in some places to add another layer of poly, but then others saying to remove the layer.  I've tried wiping with mineral spirits but that doesn't seem to make it any better.Unknown-1.jpeg.bd84030c49f9be5384c975fe56aab7d4.jpegUnknown.jpeg.4d1445f6b0754e7a0b79be572da9fa56.jpeg

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220 with a ROS is way too aggressive for sanding finish, especially the first coat! I always hand sand between coats with 320 max and usually 400 to 600 and usually don’t use a block even on flat surfaces - I feel I have more control that way. 

It looks like the wood was colored and you also sanded some of that off. If that is the case you might be stripping down to the wood and starting over. 

Also, always practice your finish schedule on a piece of scrap. 

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Yeah I'm pretty scared of using anything but a piece of sandpaper and my hand once the finish goes on. I think I always start at 320 too. Even then I sort of treat it as if I'm wiping off the piece with the sandpaper. Just removing nubs and such. 

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1 hour ago, estesbubba said:

220 with a ROS is way too aggressive for sanding finish, especially the first coat! I always hand sand between coats with 320 max and usually 400 to 600 and usually don’t use a block even on flat surfaces - I feel I have more control that way. 

It looks like the wood was colored and you also sanded some of that off. If that is the case you might be stripping down to the wood and starting over. 

Also, always practice your finish schedule on a piece of scrap. 

Righto, luckily I haven't sanded any of the wood off or the stain just didn't take to well to that area and I didn't want to go any darker. Believe it or not I did try on a piece of scrap but that scrap didn't have as many redo's as my actual project. I'm going to give another coat a shot as someone suggested and if that doesn't work it looks as if I'm going back down to stain.  I'm concerned about sanding through that veneer as wdwerker posted about a little bit ago. This will be the 4th time i've sanded it down for various reasons.  I don't feel too bad though having this been my first project with wood. Thank you all for the suggestions.

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Persistence is a good quality for a woodworker.  Sanding is the act of creating a consistent scratch pattern of smaller and smaller scratches until we reach the point that we consider the surface "smooth".  A coat of finish can resolve a lot of first or second coat issues.  Your Minwax product is not going to "burn in" to the layer beneath so, some issues can be persistent.  If you've already gone with another coat and it worked; kudos to you, read no further.

If you want to get to a smoother surface before your next coat, like others I use 320 or 400 between coats.  Usually by hand with a felt block unless I am going for a glass finish and then I use a larger hard block.  Kinda like using a long plane to flatten as opposed to a block plane if ya get my drift :).

If the 400 grit still isn't consistent enough for you (I really think it will be) you can move to 600.  the scratch pattern doesn't have to be super smooth between coats but, the more consistent the less likely something is going to 'telegraph' from one cot to the next and show.

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22 hours ago, Eric. said:

 

I usually sand 320 after the first two coats, then 500 after the third, apply a thin fourth coat then final polish with 1000 wet sand after the finish cures.

I second this. Because when I was trying to figure out finish I came here, saw Eric's method, used it and haven't had a problem since. Also ditched brushes and use exclusively rags. 

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