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Puzzling finish with varnish/tung oil

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  • Puzzling finish with varnish/tung oil

    I recently read an article about varnish finishes (I think in fine woodworking). The recipie is: 10 parts Pratt & Lambert #38 satin varnish, 10 parts pure Tung oil, 2 parts Japan drier and 2-3 parts turpentine. I made it up without the Japan drier and with 2 parts mineral spirit.

    I am finishing a desk of rustic alder and had the following very odd results. I should point out I live in AZ where its is HOT and dry right now and desk is outside on a porch which gets direct sun after 2-3PM.

    - If I apply the varnish in the heat of the day (3PM), even in direct sunlight, I get a nice satin finish. It's dry and you can rub it with steel wool within a few hrs.
    - If apply in the evening, around 8PM when its around 80-90f out, I get a very dull, flat, almost milky finish by the morning. I need to rub with steel wool and recoat.
    - If I apply indoors at 8PM (on a test peice), I get a nice uniform satin finish.
    - If I apply indoors (at a const 80f) in the heat of the day I get a nice satin finish.

    Just thought I's share this with you.

    Cheers Dennis Wilson

  • #2
    Re: Puzzling finish with varnish/tung oil

    I think the message here is to apply inside in a control atmosphere or at least in the shade. I would guess that being applied in the sunlight, that there is a reaction to the ultraviolet rays.
    I have purchased all of the components of this recipe and plan to give it a try soon on a shop cabinet. How about posting a picture of your project.
    sigpicSeldom Wrong, BUT Never in Doubt

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    • #3
      Re: Puzzling finish with varnish/tung oil

      Dennis, thank you for posting. I've been curious about this. Out here on the East coast, I think the Japan Drier would be good to use, but I don't know enough about the chemicals involved to really comment. What was your thinking behind not using it? It'd be great to see some pics of the project, by the way! Harley, don't forget to post your pics, too.
      I put it all back together better than before. There\'s lots of leftover parts.

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      • #4
        Re: Puzzling finish with varnish/tung oil

        Just a guess, but being out on a porch, some condensation might form on it when the temperature drops over night. This would cause water to form on the finish before it's fully dry. Or perhaps the temperature drop itself might be responsible.

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        • #5
          Re: Puzzling finish with varnish/tung oil

          Normally, a milky look that also decreases the gloss is a result of moisture entrapment. You said "tung oil". Is it really tung oil or is a commercial finish labeled as tung oil. (Many of the commercial finishes labeled tung oil have no tung oil in them). Depending on where you live in AZ, the temp/moisture ratio could change drastically at night due to the cool air coming down off the mountains and the oil additive could be slowing the drying time, allowing the moisture to penetrate the coating before the surface cures..

          Go
          Practicing at practical wood working

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          • #6
            Re: Puzzling finish with varnish/tung oil

            I've attached some picture of the desk. These were taken BEFORE I used the varnish/tung oil mixture, and before the drawer handles were installed. Initially I finished the whole desk with a mix of: winwax early american stain, BLO and watco danish oil (neutral). I mixed these up in different proportions until I got the depth of color I wanted. These dried to completely flat finish with nothing left on the wood surface really. Then the plan was to add a protective coat of Zar Tung Oil finish which I already had. I used this on the desk top, applied several coats and it looked amazing. The only problems were that (1) it was too glossy for me, and (2) I left the can out in the sun one day and it cooked!! This is when I found the mixture I wrote about in my first post (tung oil/#38 satin varnish).

            To answer your questions:
            Harley - when I apply in the sunlight when its 100 degrees out I get pretty good results. Its when I apply the finish at around 9PM at night outside, no sunlight and its around 80-90 degrees, when I get the dull almost milky result. Last night I had two peices of alder. I applied the finish at 9PM. I left one peice outside (90 degrees when applied and it cooled off to low 70s overnight). I left the other peice inside at a constant airconditioned 81 degrees. The outside one was dull by the AM and the inside one looked nice.

            VA: I did not use the drier because it is HOT & pretty low humidity most of the day in AZ and figured that I might not need the catalyst to help it dry. This way I can make up more of the stuff and it will have a Longer shelf life vs a few weeks with the drier added.

            TP: I wrote to the editor of Fine Woodworking and he said a similar thing. This makes sence, only in AZ we have pretty low humidity. Although at 9PM humidity starts to rise to about 30% and increases to about 65% over the next 7hrs. I guess this might be enough to cause the problem.

            Gofor: I did purchase 100% tung oil for this mixture, not tung oil finish (like thre Zar I was using at first).
            Attached Files

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            • #7
              Re: Puzzling finish with varnish/tung oil

              Beautiful desk, DW! Thanks for answering the questions and posting the pictures.
              I put it all back together better than before. There\'s lots of leftover parts.

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              • #8
                Re: Puzzling finish with varnish/tung oil

                DW....I'm in Phoenix and agree that the cloudy dull finish of from the humidity increase at night. While we don't have much moisture, at night, it will condense enough to cloud a "still wet" finish.
                I fight with my evap cooler and lacquer all the time. With the water running and any thing i'm spraying in direct air flow, I sometimes get clouding. All I can do is shoot it with straight retarder to soften the lacquer and give the moisture time to work it's way out and turn off the water and sweat it out! LOL

                Nice piece too!

                Mark
                Congratulations to Mr. "the sky is falling" Al Gore, nominated the new Village Idiot!

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