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Walnut table top finish trouble

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Forum topic by MichiganKeel posted 05-02-2016 01:56 PM 401 views 0 times favorited 6 replies Add to Favorites Watch
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MichiganKeel

14 posts in 500 days


05-02-2016 01:56 PM

I built a table top from book-matched walnut slabs. I coated it with BLO because I liked the way it brought out the grain and then topped with General Finishes High performance to create durability. BIG mistake as this was a water based poly on top of the oil and it didn’t dry evenly. (Let’s not beat me up over this ok?)
My next step then was to sand it down to bare wood, reapply BLO but then top with dewaxed shellac before the General Finishes. I did this on a test piece and it looked great. Unfortunately, even with three coats of shellac, the table is still blotchy and I believe it’s because the previous coat of water based finish penetrated and blocked the pores unevenly.
So I’m going to sand it down again and am looking for advice on how to get rid of the blotching? Running test pieces doesn’t seem to prove one technique over another as the work piece has been altered so much. So I need advice based on experience. Things I’m considering are:
1) sand off enough to get below the damaged pores. (I don’t know if this is possible as it probably soaked in quite deep in some areas) and start over again
2) somehow even-out the blotchyness by soaking in all the wood with something, presumably water based.
3) revert to an oil based poly but what do I do with the base to bring out the color?

I’m pretty lost here and this is an extremely costly mistake I’m trying to rectify. I appreciate any knowledgeable help.

-- I keep cutting and cutting and it's STILL too short


6 replies so far

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HokieKen

1812 posts in 606 days


#1 posted 05-02-2016 02:43 PM

How long did you let the BLO cure before shellac? If the oil isn’t fully cured, the topcoats will never be even. If the BLO was fully cured, you can try sanding sealer after sanding back down before applying finish.

Regarding #3, you can still use BLO for the base with poly over it. If you’re having trouble getting the poly on evenly, try cutting it 1:1 with mineral spirits and wiping it on. I’ve found that’s a pretty bulletproof way to get a good even coat with no streaks. It will take more coats to build a film though.

Good Luck!

-- Kenny, SW VA, Go Hokies!!!

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MichiganKeel

14 posts in 500 days


#2 posted 05-02-2016 02:45 PM

By the way, I’m aware of Charles Neil’s product but have not used it. Im not sure if this will solve the problem I’ve created or if his product is strictly for pre-treating wood that hasn’t been messed with?

-- I keep cutting and cutting and it's STILL too short

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MichiganKeel

14 posts in 500 days


#3 posted 05-02-2016 02:47 PM

HokieKen… As I understand it BLO takes years to “fully” cure. I gave it a week.

-- I keep cutting and cutting and it's STILL too short

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CharlesNeil

1610 posts in 3338 days


#4 posted 05-02-2016 04:06 PM

my product isnt going to help at this point, besides, walnut typically doesn’t blotch, What you have is a sporadic areas that have the BlO, and areas that since you sanded, don’t . What you need to do is to try to sand the water base off thoroughly and then apply another coat of BLO. Sounds strange I know, but you need to get the lighter areas to absorb some BLO. Oils react with the tannin’s in the wood and slightly alter the color. The slower the oils dry the more reaction you get, in your case you have areas that still have Blo and areas that don’t have as much, I suspect .

A picture would help alot , Im not sure why the High performance didn’t dry, especially if you sealed it with shellac. Shellac will also cause the a reaction with the tannin’s, any solvent based product will .

I would sand it thoroughly then do the BLO, since thats what you started with, but I would also do a small test area to be sure, and do a sample board, to test everything first.

Did you wipe the BLO back good , or was it a heavy coat , and left, also how old is the Shellac, and what was it thinned with.

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HokieKen

1812 posts in 606 days


#5 posted 05-02-2016 04:14 PM



HokieKen… As I understand it BLO takes years to “fully” cure. I gave it a week.

- MichiganKeel

True, I suppose I meant a “working” cure. To me, that means I can’t smell it and I can wipe the whole thing with a clean rag and the rag doesn’t pick up any oil. A week should be plenty of time for BLO.

Advice above^^ is about as reliable a source as you’ll find so I’d just do what Mr. Neil says!

-- Kenny, SW VA, Go Hokies!!!

View MichiganKeel's profile

MichiganKeel

14 posts in 500 days


#6 posted 05-02-2016 09:48 PM


my product isnt going to help at this point, besides, walnut typically doesn t blotch, What you have is a sporadic areas that have the BlO, and areas that since you sanded, don t . What you need to do is to try to sand the water base off thoroughly and then apply another coat of BLO. Sounds strange I know, but you need to get the lighter areas to absorb some BLO. Oils react with the tannin s in the wood and slightly alter the color. The slower the oils dry the more reaction you get, in your case you have areas that still have Blo and areas that don t have as much, I suspect .

A picture would help alot , Im not sure why the High performance didn t dry, especially if you sealed it with shellac. Shellac will also cause the a reaction with the tannin s, any solvent based product will .

I would sand it thoroughly then do the BLO, since thats what you started with, but I would also do a small test area to be sure, and do a sample board, to test everything first.

Did you wipe the BLO back good , or was it a heavy coat , and left, also how old is the Shellac, and what was it thinned with.

- CharlesNeil

Charles, thank you for weighing in! I hoped that you would. My second attempt at this was as you suggest to use BLO to even out the saturation. I applied two quite heavy coats and waited two days . The botching was not evident at this point. I then padded on three coats of Zinser seal coat that was not thinned but had several drops of transtint dye . This was a brand new can. When sanding these layers this is where the blotching appeared.
I did spray some GF on top at this point which had no impact to the color and did dry.
Do you have any suggestions for how to get the wood to evenly accept the oil? Or if I’ve sanded off some oil is it preferable to try to sand it all? Would you then top with shellac? .
Finally I feel as if I’ve overworked the wood already. Doing a sample to a small area feels like it will exacerbate the problem?
Thank you again!

-- I keep cutting and cutting and it's STILL too short

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