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Thread: Polyurethane Over Bolied Linseed Oil OK For Ash?

  1. #1
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    Polyurethane Over Bolied Linseed Oil OK For Ash?

    Is it alright to use polyurethane over boiled linseed oil for an Ash project? Some parts of the project (AV equipment rack) have been "ebonized" (Speedball brand gives very nice results - jet black) and I am planning to protect them with a Minwax polyurethane. For the other ("non-ebonized") parts of the rack, I am planning to use boiled linseed oil - again with a polyurethane coat. Does this sound reasonable?

    In the past, I've used paste wax over boiled linseed oil (for a cherry project); I don't think it's reasonable for some parts of this project to have a wax finish and other parts to have a polyurethane finish - which is why I ask. I also don't think a full wax finish (i.e., wax over both the ebonized and boiled-linseed-oiled parts) is a good solution. Is it?

    Thanks much.
    Kofi

  2. #2
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    If you're using an oil base polyurethane, you can apply it over BLO. If using the BLO is not to enhance the grain, IMO it would be an unnecessary undercoat to oil base polyurethane. As a note to oil, pure Tung oil will not impart an amber tint as BLO will.
    .

  3. #3
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    Quote Originally Posted by cabinetman View Post
    If you're using an oil base polyurethane, you can apply it over BLO. If using the BLO is not to enhance the grain, IMO it would be an unnecessary undercoat to oil base polyurethane. As a note to oil, pure Tung oil will not impart an amber tint as BLO will.
    .
    I didn't realize I could apply the (oil base) polyurethane directly over the Ash. To maintain the high contrast of the project (ebonized with non-ebonized Ash), could I simply forget about the BLO and just apply the polyurethane diectly to the non-ebonized parts? Is there no advantage then to the BLO or Tung oil? Yes, I'd rather not have the amber tint in the non-ebonized Ash.

    You are probably recommending then, that if oil is necessary, Tung oil is preferred to maintain the color of the wood? So, is the oil necessary?

    Thanks much.
    Kofi

  4. #4
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    Quote Originally Posted by partialresponse View Post
    I didn't realize I could apply the (oil base) polyurethane directly over the Ash. To maintain the high contrast of the project (ebonized with non-ebonized Ash), could I simply forget about the BLO and just apply the polyurethane diectly to the non-ebonized parts? Is there no advantage then to the BLO or Tung oil? Yes, I'd rather not have the amber tint in the non-ebonized Ash.

    You are probably recommending then, that if oil is necessary, Tung oil is preferred to maintain the color of the wood? So, is the oil necessary?

    Thanks much.
    Kofi

    Lets just say I prefer Tung oil for that reason. If I say it is preferred, some will reply here and ask for my source for that statement. So, to prevent a ruckus, I'll just say that's what I use.

    Depending on what you're after, like I stated in my previous post, if you want to enhance the grain, start with 100% pure Tung oil, NOT Tung oil finish. You can thin the Tung oil with mineral spirits, or naptha (for quicker dry), about 30% for the first application to get better saturation. Allow to sit for about 30 minutes and wipe. If you wish to apply a second treatment, use a 15% - 20% diluted solution, and allow to sit for about 30 minutes and wipe. Allow a cure time between applications. For the application of the oil base polyurethane, the first application can be thinned the same way as the oil. I usually apply it as a wipe on, using a clean lint free "T" shirt type material (cotton or blend, doesn't matter).

    The oil base polyurethane can be used as a stand alone finish. It doesn't get wiped off like the oil. Allow each application to cure. I also suggest you do samples out to the final finish so you can see how they look totally finished.

    Depending on the amount of film build you want, the poly applies easier when slightly thinned. So, as a disclaimer, this is what I use and what I do.
    .

  5. #5
    SARGE..g-47 Guest
    BLO and tung oil are used to pop grain, PR. As Cab mentioned.. use the Tung to avoid the amber tint.. use BLO if you want it. If you have ebonized as you suggested.. neither may be necessary before you use poly.

    Now if you want it clear.. water base is your man but don't ever use it over BLO or tung. If you do use either oil before the poly.. allow a week to dry to be sure they have cured. As Cab mentioned.. tung takes twice a long to cure as BLO.

    But.. I have a question. Are you going to use water base or oil base poly on the ash. You didn't want any amber efffect and if you use oil base.. you will get amber effect as opposed to the water base.

    Good luck with the project...

  6. #6
    I use BLO and Poly on pine, I like that nice warm tone I get.

  7. #7
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    I have used water based finish over boiled linseed oil but it was not on ash. The oil has to be completely dry so I waited a week. That might not be long enough on an open grained wood like ash. Oil based would be safer.

    Jim

  8. #8
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    Quote Originally Posted by SARGE..g-47 View Post
    ......
    Now if you want it clear.. water base is your man but don't ever use it over BLO or tung. If you do use either oil before the poly.. allow a week to dry to be sure they have cured. As Cab mentioned.. tung takes twice a long to cure as BLO.

    But.. I have a question. Are you going to use water base or oil base poly on the ash. You didn't want any amber efffect and if you use oil base.. you will get amber effect as opposed to the water base.

    Good luck with the project...
    OK, I see what you mean guys. I just tried the BLO alone (on a first wood sample) and the oil-based polyurethane alone (on a second wood sample) and both developed that amber tint. I'd rather not have it, so I'll try and find some water-based polyurethane tomorrow and try that as well.

    I'm now wondering about water-based poly over pure Tung oil....The pure Tung oil seems difficult to find at HD or Lowes (they do have Tung oil finish - which I've been cautioned against by cabinetman.)

    Thanks much.
    Kofi

  9. #9
    SARGE..g-47 Guest
    Tung oil finish is somewhat deceptive as Cab mentioned. PR. Most tung oil finish is a mixture that has some tung oil but also resins such as poly or varnish. Opps.. poly or varnish which cycles back around to a slight tint of amber.

    Not sure how carries the pure tung oil as I don't use it straight. I do use Watco Danish to pop grain on many applications with oak to pop grain and then cover with either Shellac or poly as I lile a hint of amber on the red oak I use often. Jeff Jewitts site Homestead Finishing.. Highland Woodworking or Lee Valley most likely carry it.. Do a Google search if interested.

    BTW.... I did a hickory work-bench top once with pure tung oil. About 3-4 coats as I had never used it straight at the time. Wipe.. wipe.. wipe several times a day for about two weeks before the oil finally cured and quit coming up a beads on the surface.

    Oil alone is a very thin finish that gives little protection of value IMO if you really need a protective finish. But... it will sure pop grain on certain species and I use it almost every project to do so.. but I do allow it to cure for a week after application and I wipe beads of oil off every 3 hours or so the first day and then around every 6 hours the second before the beads usually stop rising.

    Get yourself a good finish book by Jeff Jewett of Flexner. Lots to learn if you go beyong using poly every application.

    Good luck...

  10. #10
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    Quote Originally Posted by SARGE..g-47 View Post
    Not sure how carries the pure tung oil as I don't use it straight.
    I've seen pure tung oil (and tung oil finish) at both my local Rockler and Woodcraft.

    g.
    "Be excellent to each other."
    Bill & Ted

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