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Thread: Removing Tung Oil from Grooves?

  1. #1
    Join Date
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    Removing Tung Oil from Grooves?

    I am putting a Tung Oil finish on this valet, a project for a grandson. I decided to apply the finish before assembly so as to avoid having to deal with wiping oil into and out of interior corners.

    To protect the glue joint faces, I taped off the ends of the front and back pieces that fit into the dadoes in the sides. I also taped the 3/8" dadoes on the inside faces of the sides (face down in this picture). I did not tape the 1/8" x 1/8" grooves that the box bottom and tray bottom fit into - figuring if I was careful, I could keep the Tung Oil out of those narrow grooves. I was wrong, after four coats, most of the groove surfaces have oil on them. The bottoms are 1/4" ply with a rabbet on each edge to fit into the grooves. I was planing on gluing the bottoms in place for added strength as the dadoes in the sides for the front and back are only 1/8" deep deep.

    Two questions. Will the oil in the grooves adversely affect the glue joints to the point the joint is likely to fail? If so is there any way to remove Tung Oil from a 1/8" groove without damaging the finish on the adjoining faces?

    Thanks,

    Tom
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  2. #2
    Join Date
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    A panel in the grooves would not normally be glued so the assembly will resist wood movement. Unless you have a good reason to glue the panel and have designed things to deal with said wood movement, I wouldn't worry about the oil in the grooves...because at this point, there's really not much you can do to recover from this. BTW, oil or an oil finish on the inside of a closed structure is going to retain the smell of the oil/oil finish off-gassing "forever". You may want to consider sealing it with shellac to avoid transfer of the odor to anything your grandson might keep in the piece that can absorb odors.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  3. #3
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    I do have a question? What kind of Tung Oil are you using. Many products labeled as Tung Oil Finish aren't really tung oil but are oil and varnish mixed, or just varnish. Formby's for example is varnish, not oil or oil/varnish mixture. Oil was an ingredient going into the chemical manufacturing process that made the varnish. The issue is that varnish left in grooves could act more like a glue than would oil. Since panels of solid wood need to be floating in the grooves as it changed with seasonal moisture changes.

  4. #4
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    I would take Q-tips dipped in lacquer thinner and clean the grooves, the go ahead and glue in your plywood bottoms if you want. The lacquer thinner should remove the majority of finish in the grooves to give a decent grip.
    Lee Schierer
    USNA '71
    Go Navy!

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  5. #5
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    Jim, thanks for the tip on sealing with Shellac.

    Steve, it is Hope's 100% Tung Oil.

    Lee, I'll try the lacquer thinner and go from there.

  6. #6
    Join Date
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    I concur with Jim - you shouldn't glue in the bottom. This allows for seasonal movement. So the oil in the grooves won't affect the overall strength of your piece.

    Jim also makes a good point about a top coat of shellac. I have a couple of jewelry boxes that I completed with an oil finish back in 2016 and can still smell the oil on the inside of the boxes. A coat of shellac will greatly reduce this problem.

    TedP

  7. #7
    Quote Originally Posted by Steve Schoene View Post
    I do have a question? What kind of Tung Oil are you using. Many products labeled as Tung Oil Finish aren't really tung oil but are oil and varnish mixed, or just varnish. Formby's for example is varnish, not oil or oil/varnish mixture. Oil was an ingredient going into the chemical manufacturing process that made the varnish. The issue is that varnish left in grooves could act more like a glue than would oil. Since panels of solid wood need to be floating in the grooves as it changed with seasonal moisture changes.
    Formby's Tung Oil Finish is Tung Oil Alkyd Varnish, diluted with solvent. However, it doesn't contain raw or unassociated tung oil.
    Note: When I ran the Reed Study (I'm a chemist), we couldn't find a single wood finishing product that mentioned "tung oil" in its label that didn't contain tung oil, either associated (fully cooked varnish) or unassociated. All tests were performed using gas chromatography.

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