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Hi all,

I’m having an issue with finishing a walnut coffee table and hoping to get some guidance/help.

Here’s the problem: some of the edges of the coffee table top are showing a pale color around the rim. It’s hard to determine whether this is from sanding or from build up of polyurethane around the rim or something else. I’ve included some pictures of the worst spots.

Here’s the process I followed for finishing the table:
  1. Rubbed on and wet sanded (320/400) several coats of Watco Tung Oil blend, wiping off the excess and scuffing with 0000 steel wool in between coats. I waited 24-48 hours between coats and allowed to sit and cure for 2 weeks.
  2. Applied 2 coats of dewaxed shellac as a sealer and sanded lightly.
  3. Applied 4 coats of Varathane water-based polyurethane, using a nylon brush and sanding (400) lightly in between coats. Typically 24 hours between coats.

The problem I’m seeing started to develop after the 3rd coat of polyurethane. To note, I’m doing this work in my basement, which is on the cooler side here in the northeast.

So far the following possible causes come to mind, though all could be wrong:
  1. In sanding, I accidentally sanded through the finish around the edges, so these lines are natural wood showing through. (This feels unlikely, since I never sanded the edges very intensely.)
  2. There is some kind of moisture underneath the polyurethane that is starting to show through. (Hopefully this isn’t it.)
  3. I applied the polyurethane too thickly and it pooled at the edges of the table. (I thought this might be the case after the lines first appeared, so I sanded more intensely and reapplied the poly – no significant change and may be worse in some spots.)

Looking for any help you may be able to offer in diagnosing and fixing the problem. Thank you!
 

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where's my table saw?
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Village Idiot
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You sanded through the finish at the corners. Easy to do honestly, finishes shrink a bit as they dry and the finish at the edges always ends up being pretty thin because of it. It takes almost nothing to do through too, a tiny bit too much sanding can do it. Polyurethane is particularly easy to have it happen too. Since coats of poly dont 'melt' into each other like solvent based finishes like lacquer do, each coat of finish will settle as its own distinct layer, and if you sand through a layer of the finish it shows up as a white witness line.

Dont ask me how to fix it, you wont like my answer. Typically if a finishing mistake affects the stain/color, i have to start over from scratch since the touched up areas just dont match. Theres a reason i avoid complex finishing schedules. Seldom do i do anything more than spraying a few coats of shellac/lacquer
 

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I've had finishes pool at the edges (it's called "fat edge") and then be gummy when sanded and not sand out like the rest.

I agree with the others that it looks like you've sanded through to the wood, but if you put more poly on the bare wood, it should begin to look like the rest of the finished area - if it's not, that's perplexing.

The witness lines that Epicfail mentioned are a concern, but if you sand without such a heavy hand from here on out, you just might get away with it.

I'd try using a small artist brush to put a few coats of poly on just the sanded through areas. If that evens it up, then I'd continue to add more coats to the whole thing. If it works out, you're golden; if not, you're back to stripping and starting over.
 

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You can't just apply more clear ......

The stain is gone along the edge, so you need to stain/color it to match before adding any more clear. Clear will just enhance the light VS the dark colors that are there now.
 

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Discussion Starter #6
Thanks, all. Would it makes sense to just touch up these exposed areas with a little of the tung oil blend so that they appear to be the same shade as the rest of the table?
 

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The stain is gone along the edge, so you need to stain/color it to match before adding any more clear. Clear will just enhance the light VS the dark colors that are there now.

Great point. I didn’t see that he had mentioned using stain, but missed that the first coat was the Watco.
 

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Looks like you sanded through. More likely to happen if you sand to aggressively, too coarse grit, or don't use a sanding block .

Try re-oiling the area it might match up enough suit you. Another option is stain, dye, or toner, but that is a much more tricky.

If nothing works, one solution is to simply chamfer the edges back to good wood, reapply the oil.

The mark of a true craftsman is how well they fix their mistakes!
 
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