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Thread: poly over oil?

  1. #1
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    poly over oil?

    I have a piece of maple that I turned over the weekend. I used Minwax Tung Oil Finish (not pure tung) it and plan on buffing it. I have a couple of questions: can I put a couple of coats of poly over it and if I did should I do anything to the wood before hand? I was just thinking that some of the stuff you guys do looks like glass, should I buff (but skip the wax) so the wood is extra extra smooth, then poly, then buff all three steps? How long should I wait between tung oil, poly and buffing?

    Thanks. -w

  2. #2
    Oil over oil is fine. Poly resin requires a bit of "tooth" to mechanically bond. The old 320 scuff should do between coats.

  3. #3
    I use Minwax Wipe-On Poly over Watco all the time and it works great for me. The directions on the Watco say to wait 72 hours if you wish to apply a topcoat such as Polyurethane. I usually end up waiting a little while longer to make sure the Watco is dry - it is usually dry enough once I can no longer smell the Watco.

    I would suggest following George's directions and lightly sand between coats. Once you have applied however many coats you want - and they are dry - then buff everything out using all three steps.

    Should work just fine!
    Steve

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  4. #4
    I have used Gel Poly over Watco on a lot of my pieces. Just let the Oil fully cure and you should be fine.
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  5. #5
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    Quote Originally Posted by Jim Ketron
    I have used Gel Poly over Watco on a lot of my pieces. Just let the Oil fully cure and you should be fine.
    Jim, another newby question....why put poly over the Watco oil finish, why not just go with the poly from the start?

    Dale

  6. #6
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    You may get more pleasing results if you use a non-poly varnish...it will buff out much nicer since it's not as abrasion resistant...the key attribute that poly brings to varnishes based on it. While a lot of folks use poly on things like turnings, it's really best for floors and other high-traffic;high-demand applications. Unfortunately, it's also the only accessable varnish for many, at least in the 'borg stores. Marketing at its best.....

    Oh, and the Minwax "Tung Oil Finish" already is a wiping varnish. If you need more build, just put on a few more coats.
    Last edited by Jim Becker; 02-05-2007 at 10:38 AM.
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  7. #7
    Quote Originally Posted by Dale Gregory
    Jim, another newby question....why put poly over the Watco oil finish, why not just go with the poly from the start?

    Dale
    Any Oil finish will POP the grain better than just poly. If I have a piece with lots of figure/curl I will almost always use an Oil finish on it.
    Have Chainsaw- Will Travel

  8. #8
    Couple of thoughts. Urethane resin is, of course mixed with oil as a vehicle if you're using oil-based polyurethane. Watco is back to using phenolic resin, IIRC, and of course the Tung Oil Finish has a resin as well. Think it is alkyd. So they all have oil, though it may vary from tung to soy to linseed, and all have solids to harden and build a surface. Wipe-on Poly, according to FWW tests has the highest solids content.

    Hardness has nothing to do with gloss. Glass is hard, and it can be made quite smooth, as can wax, which is pretty soft. Likewise, anything which cuts down on surface scatter by filling or bridging minute scratches and pores as oil does will enhance contrast and "pop" the grain. Once again, a recent article in FWW might help understanding what's happening.

    What counts most in clarity of finish are other additives designed to scatter light within the finish itself, or polymer size in the oil or resin. They also soften the total film a bit, which is why many choose to use gloss varnishes free of scattering additives and then use a surface scatter created by abrasives to dull back the surface. Gives them the hardness and wear resistance they want without the surface shine.

  9. #9
    Quote Originally Posted by Dale Gregory
    Jim, another newby question....why put poly over the Watco oil finish, why not just go with the poly from the start?

    Dale
    Another newbie question. Do you have to put poly over Watco? or is Watco good enough by itself?

  10. #10
    Just keep in mind some finishes are top only ( urethanes , varnishes, laquers) and some like pure tung is a deeper treatment for the wood, finer stuff deserves the tung as it conditions deeper than the urethanes etc, also I think it gives better looking finishes ( more like a French style finish) or a hand rubbed , but way less protection for the wood surface . My rule is show and go are tung, stay and play are urethanes etc.
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  11. #11
    Quote Originally Posted by Paul Engle
    Just keep in mind some finishes are top only ( urethanes , varnishes, laquers) and some like pure tung is a deeper treatment for the wood, finer stuff deserves the tung as it conditions deeper than the urethanes etc, also I think it gives better looking finishes ( more like a French style finish) or a hand rubbed , but way less protection for the wood surface . My rule is show and go are tung, stay and play are urethanes etc.
    Sounds like a bit of advertising influencing your decision. Penetration is dependant on viscosity, not on the composition of the oil itself. Lower the viscosity by thinning or warming and you will get the oil modified urethane in as far as any oil of similar viscosity. Principle behind the "Danish oil" thinned oil/varnish mixtures.

    I regularly use two coats of thinned urethane (Wipe-On-Poly) as a use finish, scuffing off any surface sheen. With most woods and my sanding schedule, there's not much on the surface after two coats.

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