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Keeping Poly Fresh

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  • Keeping Poly Fresh

    I've tried Cabot, Minwax, and General Finish products and I thought I liked the General products the best. I recently bought a quart of the Arm-R-Seal Oil and Urethane Topcoat and have been disappointed that it forms a film in the bottom of the can when about 2/3 of the material has been used. I only bought the can about a month ago and I've used it several times over the last few weeks. Any tips on how to keep that last bit of finish fresh?

  • #2
    Re: Keeping Poly Fresh

    Place some Siran Wrap over the top of the remaining poly before you close up the can.
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    • #3
      Re: Keeping Poly Fresh

      Bloxegen

      is a compressed can of inert gas that will replace the oxygen in a can and usually keep it from skinning over,

      the oxygen reacts to the resins and causes them to skin over many times, even tho the can is closed tight,

      here are a few other ideas
      http://forums.finewoodworking.com/fi...gen-substitute
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      • #4
        Re: Keeping Poly Fresh

        I reuse small water bottles. I purchase by the gallon and fill up the water bottles with a funnel. The trick is to squeeze the bottle until the poly is near the lid and then cap it off so all the air is out. They will keep for years that way.

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        • #5
          Re: Keeping Poly Fresh

          I forgot to mention that some of the bottles I actually keep the air in them and I will rotate them every 48 hrs and open them back up and let fresh air in. I have found that it will thicken up the poly and allow for less coats on tough applications. For example I made a rocking chair for my wife when my first son was born. I did this so it would be easier to apply on all the round areas and and the areas I had carving done on.

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          • #6
            Re: Keeping Poly Fresh

            Dan, if that's working for you then that's great. Polyurethane is a resin that cures by cross-linking. Depending on the material you're using that thickening could be due to some solvent loss ... or it could be due to it starting to cross link in the can, it can get to the point where you will have all sorts of problems including poor flow out.

            Personally, and I know this isn't for everyone, I ONLY spray clear finishes. And I got away from poly long ago. It's pretty durable stuff, but hard to spray and iffy to repair. I now use only catalyzed lacquers or my favorite, conversion varnish. These are the materials used by commercial cabinet makers. You get a nice thin coating that doesn't have that plastic look, they are very durable, a dream to spray and easy to repair. Not cheap, though (neither is poly) and only practical if you have a good spray rig. Try it once and you'll never buy another can of polyurethane!

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            • #7
              Re: Keeping Poly Fresh

              "Poly" varnish and all regular varnishes cure by oxidation. The original tack time is due to solvent evaporation, but the hardening is due to reaction with oxygen. Un-catalyzed lacquer and shellac dry by evaporation, so can be redissolved by adding solvent.

              Bloxygen, or any other inert gas sprayed in right before putting on the lid will limit the amount of oxygen so the top does not harden. However, when you open the can and stir it, some oxygen will be blended into the varnish and remain.

              For best results, open can, stir, and then decant what you need and immediately close the can (using bloxygen, et al will increase your chances of it lasting).

              Some thick varnishes will defy most efforts, so buy those in smaller containers. Behlens Rock Hard table top finish is a phenolic varnish that is excellent quality, flows well, dries tough, and also defies any attempt I have made to keep it from skinning over. Even though more expensive by the quart, it is still cheaper than throwing away a quart when buying a gallon.

              Dan Lawrence's idea is outstanding,(Thank You Sir), and I will definitely use that in the future. May still get by with the gallon buys!.

              Realize that clear gloss finishes that do not have flattener additives, etc, usually work just fine if you break the skin and strain the liquid underneath. If it is a semi-gloss, satin, etc with flatteners, though, they will settle out and have more effect as you loose the pure varnish through the amount that has skinned. Same goes for pigmented coatings.

              Go
              Last edited by Gofor; 11-10-2010, 07:20 PM.
              Practicing at practical wood working

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              • #8
                Re: Keeping Poly Fresh

                A trick I learned many years ago and it has worked very well for me is, take a soda straw put it in the can, lay the lid on then take a good breath to fill your lungs then blow into the can, then slip the straw out and close the lid. I have used this method for not only poly but for paints to.

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                • #9
                  Re: Keeping Poly Fresh

                  Originally posted by JWM View Post
                  A trick I learned many years ago and it has worked very well for me is, take a soda straw put it in the can, lay the lid on then take a good breath to fill your lungs then blow into the can, then slip the straw out and close the lid. I have used this method for not only poly but for paints to.
                  Originally posted by DanLawrence View Post
                  I reuse small water bottles. I purchase by the gallon and fill up the water bottles with a funnel. The trick is to squeeze the bottle until the poly is near the lid and then cap it off so all the air is out. They will keep for years that way.
                  Think what JWM and Dan said should do the trick ... and it's cheap
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