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  • water versus oil based polyurethane

    Hi,

    I would appreciate any advice on water versus oil based polyurethane. I am thinking water would be better due to less yellowing but am concerned about raised grain. Thanks.

    Best regards,

    Henry

  • #2
    After years of using oil based polyurethane, I have used water based poly for the last couple projects. It is a dream to apply - so easy that it is now my standard for the inside of drawers and other "optional" finish areas. Raised grain is not a significant problem. However, I am disappointed in it for the finish - or maybe I haven't learned to use it right.

    The water based poly dries quickly - but perhaps too fast - before it has a chance to flow to perfectly even. Applied heavy or light. With bristle or foam brush. And it doesn't get as hard - days later I had trouble sanding it smooth (in frustration because the many coats weren't pretty). And the padding used to deliver some furniture weeks later left marks in the finish.

    We love the convenience of water based poly, but are struggling with what it takes to make it look good.

    Comment


    • #3
      Like every category of product, there's better and, uh, not-so-better in this one.

      Charlie ran into a problem that arises from a common misconception about waterborne varnish in general. There are two steps in the lifespan of a varnish, drying and curing. We are used to accomodating this with oil-based, dry is when dust stops sticking, cured comes much later (easy way to tell is when the finish stops smelling strongly.)

      Waterborne finish is similar. Drying occurs very, very quickly. Curing time is much, much longer. Typical cure times on high-quality waterbornes are in the couple weeks to couple months time frame. To some extent, the higher end the product, the longer the cure time. This is partly because the high-end products cure much harder than lower end.

      You mention a lack of yellowing. This is referred to as "whiteness" in finishes. A finish that contributes no color at all being called "water-white". You need to watch for this, because many waterborne finishes are now being tinted to approximate the color of an oil-based finish. This is because some woods look frankly terrible under a water-white finish. The most outstanding example of this in common North American hardwoods is Walnut. Under water-white finish, it looks bleached out and cloudy.

      Waterborne finishes are getting better almost daily. Air quality regulations are the driving force, the day when commercial operations aren't allowed to use conventional solvent based finishes is coming, just a matter of when. As small-shop woodworkers, we get to benefit from this with new products that are safer and easier to use than before. But, you'll need to hunt a little to find the premium products.

      Two companies that are notable in their waterborne products are Fuhr International ( http://www.fuhrinternational.com/ ) and Target Coatings ( http://www.targetcoatings.com/ ). Both these lines are carried by, among others, Jeff Jewitt's Homestead Finishing, http://www.homesteadfinishing.com . These high-end products are simply miles from the waterbornes you will find on the shelves of the local home improvement center, almost no comparison at all.

      Dave
      Waterborne fan [img]smile.gif[/img]

      Comment


      • #4
        Thanks for the help, I really appreciate it.

        One more question:

        Should kitchen cabinets be sealed on all sides or only those visible.

        Best regards,

        Henry

        Comment


        • #5
          I seal all sides of everything whenever possible. I wouldn't take incredible care with parts guaranteed to never be seen, like the wall side of backs.

          I've seen even high-quality plywood warp because one side was finished and one side left raw.

          Dave

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          • #6
            Charlie and Dave, thank you for posting your advise. It is helping me make informed decisions on how to proceed with my cabinets. I will definitely seal all sides - I've put too much work into these and would hate to see them warp. Still haven't decided on the finish though.

            Best regards,

            Henry

            Comment


            • #7
              Dave, Thanks for your info on water-based varnishes.

              I have been using Varathane's version of a water-based, exterior varnish - Diamond something or other. I have had trouble, though, getting an even application with the first coat. I'm using it on recycled and resawn redwood, glued into panels. The wood is very absorbant and also darkens considerably when a finish is applied. The problem is that the finish dries so quickly, if the first brush stroke is not really flooded on, it seals the wood before the next stroke hits that part of the panel. The uneven sealing then prevents even absorbance of the first coat, and leads to uneven darkening. So there are light and dark brush strokes showing thru from the first coat.

              I am wondering if you or anyone else has had similar problems, and if the Fuhr International and Target Coatings brands dry slower and prevent that problem.
              Tony<br /><a href=\"http://www.mindling.com/passages\" target=\"_blank\">www.mindling.com/passages</a>

              Comment


              • #8
                I'm afraid I can't help much, Tony. I'm unfamiliar with Varathane's product (though I've heard good things about their higher end ones) and also unfamiliar with redwood. Kind of a double-whammy of ignorance.

                The best advice I think I can give would be to call up Fuhr or Target. They both have excellent support staffs and should be able to give you the straight scoop.

                Dave

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