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I need help with adhesives

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  • #16
    Thanks, Dave. I can definitely see not using it on furniture (I don't, either), and I was aware of the foaming problem. I just wasn't sure if there was something I wasn't aware of that would eliminate its uses altogether (some safety problem or inherent flaw in it). It seems like it could be beneficial for gluing plastics to wood for certain things, etc.


    • #17
      I'm building a 14' wooden boat using two part epoxy by System Three. I recommend it highly for waterproof, high strength applications. If you want to use it as a filler you must mix wood flour, extremely fine sawdust, with it until you get a consistancy that will spread, fill voids, and not run. Cures pretty quickly so only mix an amount that can be used in about 10-15 minutes depending on the ambient temperature. During the cure it is exothermic but doesn't get hot enough to be a problem in woodworking applications. It is UV sensitive so an opaque overcoat is required if it will be subject to sunlight, don't know about the UV wavelength in flourescent lighting over an extended time. System Three is very good about providing all the necessary information for the use of their products and have an excellent help desk. Available at Woodcrafts for one source.


      • #18
        There are a couple reasons that I tried Gorilla glue on furniture... When dry, it can be sanded (without turning gooey from the heat, like yellow glue). And it takes stain (not an exact match for the wood, but much closer than a yellow glue line).

        But, having used it for a few projects, I had my first joint failure. Maybe Gorilla glue is theoretically stronger than yellow glue, and maybe my technique wasn't perfect, but I would have been extremely surprised if that joint had failed with yellow glue.

        Gorilla glue technique is harder because it stains skin so badly and is expensive. With yellow glue you can glob on plenty, clamp, and easily clean the squeeze out (sometimes I think I discard more yellow glue than I actually use, but at $12 per gallon, who cares). With gorilla glue you only apply a small amount to one side of the joint, and have no solvent for cleanup.

        So I am saving the Gorilla glue for waterproof needs, and will clean up my yellow glue more carefully so that I don't worry about stainability or sanding.


        • #19
          Maybe Gorilla glue is theoretically stronger than yellow glue

          A glue line is measured in fractional thousandths of an inch. We could consider the purpose of the glue is to "weld" the two pieces of wood together. Yellow glue, properly applied et cetera, forms a bond that is stronger than wood itself. Any further "strength" is irrelevant.

          When dry, it can be sanded (without turning gooey from the heat, like yellow glue).

          I recommend cutting (as with a chisel) or scraping off excess PVA glue. Eliminates the heat issue, and gets the job done much faster to boot.

          Liquid hide glue is an alternative that doesn't share some of the drawbacks of PVAs. It does have its own set of contraindications, though...



          • #20
            "...forms a bond that is stronger than wood itself"

            Yup. Part of my wake up call, and why I am back to yellow glue.

            "I recommend cutting (as with a chisel) or scraping off excess PVA glue. Eliminates the heat issue, and gets the job done much faster to boot."

            Or even easier, wiping with a damp rag before it sets. It is close to the point where I will be grain raising anyway, so the dampness doesn't matter. But even with the surface clean, I got a thin goo line on the drum sander when I sanded a table top. Apparently it melted the PVA as it made dust of the wood around it.

            "Liquid hide glue is an alternative that doesn't share some of the drawbacks of PVAs. It does have its own set of contraindications, though..."

            I used hide glue 40+ years ago, and I guess I was hoping that, with stainability and sandability, Gorilla glue was a modern replacement to the hot stinky stuff (I must have been scarred to remember it from that long ago). Hide glue is still on my list, but way, way down the list with Gorilla glue.


            • #21
              wiping with a damp rag before it sets

              Careful to not soak the PVA right into the pores of the wood. Talk about the gift that keeps on giving, that can leave a discoloration that about nothing gets out if you aren't careful.

              used hide glue 40+ years ago ... hot stinky stuff

              Charlie, it is my pleasure to introduce you to Titebond Liquid Hide Glue.

              Unlike hot hide, this is liquid at room temperature. Also has a long open time, longer than PVA. Although it has a similar smell to hot hide, it isn't noticable since it isn't hot. Lower gram strength, but still a good strong glue.

              Short shelf life. Buy small bottle, check date on bottom. Throw out when a year has passed. The indicator that you've used out of date liquid hide is that it doesn't harden, not good.



              • #22
                Dave, about that liquid hide glue.

                What kind of strength are we talking about? If it still falls into the "bond is stronger then wood" category, then (of course) being a little less stronger then PVA would matter so much.

                Also, what are the other plus and minuses of the stuff? Mainly in comparison to Titebond and Titebond II? And is the liquid hide glue more sandable and stainable then PVA?

                Lastly, what is the shelf life for Titebond and Titebond II?


                • #23
                  Actually, in their test documents, Franklin lists the strength of Titebond, TitebondII, and Titebond Liquid Hide at almost identical at room temperature (3600, 3750, 3591 psi respectively). The percentage wood failure is likewise almost identical at a little over 70%. Liquid hide glue is a little less strong than hot hide, which is way strong stuff.

                  Pros and cons, starting with your specifics:

                  is the liquid hide glue more sandable
                  I find it easier to sand hide glue. It is much harder than PVA (think glass rather than rubber), so it sands cleaner. The heat from sanding is a problem for either, though, have to be careful there.

                  and stainable then PVA?
                  PVA really doesn't take a stain at all. Hide glue will, but not like wood does (in general, it will take a water-based dye almost the same). So I guess "better" is a fair description, but I still would recommend completely removing any excess.

                  The primary indication to not use hide glue is water exposure, which will turn hide glue back into a liquid.

                  Water exposure isn't the huge problem many would think, on a piece with a film finish and tight fitting joinery, the glue just isn't exposed to much water. I probably wouldn't use hide glue on a bathroom vanity, but general use furniture I wouldn't have a problem.

                  A pro of hide glue not previously mentioned is that it doesn't "creep". PVA is a semi-hard plastic, and over a period of years can ooze slightly out of a joint, leaving a ridge that can be felt even through a film finish. Very annoying. This doesn't happen with hide glue.

                  Another nice feature comes about should a joint fail. Experience tells us that hide glue joints eventually fail, often somewhere around the 100-200 year point. When this happens, repair is made easier by a neat property, new hide glue will stick to old hide glue. This isn't the case with PVAs, where the joint needs to be cleaned completely to get a new bond. Since cleaning off all the glue pretty much requires removing some wood, the joinery may no longer fit properly. PVAs haven't been around long enough to know when they will typically fail from age.

                  Franklin lists the shelf life of Titebond and Titebond II as one year, but that's silly. The stuff is usually good for at least three years on the shelf, if kept sealed and in a reasonable temperature. Getting it very hot, or freezing it, is very bad for PVA glue.



                  • #24
                    Just to put out my 2 cents;

                    I've never had luck wiping glue off with a damp rag. Just made a horrable mess of things. What I do now is leave the glue up laying flat, and let the squeeze out bead jell up. Then peel it off with a razor sharp putty knife.

                    PVA yellow seams to set up faster than white for me. On dense woods like maples, squeeze out soaking in just doesn't happen with yellow. Soft woods like pine will drink up the squeeze out. Just be stingy and give a thin coat to the mating surfaces.

                    If it all possable, leave your stock a little thick, I try to anyways. Touch one side up with a plane if needed to regain flatness, then shoot it through the planer. I know not all applications are subject to this method, but a finished thickness after glue up gives some dandy results.
                    John E. Adams<br /><a href=\"\" target=\"_blank\"></a>


                    • #25
                      My experience is just the opposite of Woody's so there is some room for experimenting. Or maybe we are using different wood - I mostly use black walnut, some cherry and maple, no soft woods.

                      When I have left the PVA glue to bead up, I have discovered how it really is stronger than wood... If I scrape, it sometimes pulls wood fibers with it. If I cut (sharp putty knife or chisel), the glue is still in the wood pores, giving me a wider line that is impervious to stain.

                      A year or two ago I started cleaning the area immediately after clamping (taking the lead from Norm Abrams). If I have a lot of squeeze out, I use a putty knife to get the bulk off, then thoroughly clean with a wet rag. Very thoroughly clean, rinsing the rag often. Even using a putty knife to get the rag into the corners. And have never since had a surface glue problem. As discussed elsewhere, if I am doing the final sanding after glue-up, then I sometimes get a line of melted glue on the drum sander, but it is very narrow, and seems to come from the glue line itself, as I sand the wood away from it, rather than from any glue left on the surface.


                      • #26
                        Originally posted by Charlie P:

                        With gorilla glue you only apply a small amount to one side of the joint, and have no solvent for cleanup.
                        Actually, I find acetone cleans off urethane glue while it's still fresh (and works well for epoxies, also), but after it gets at least partially cured nothing short of fire, abrasion, or time is going to remove it. Remember, acetone is toxic through skin and lungs, will defat your skin (leaving white patches), and is flamable with a very low flash point. (In fire brigade class we were told that acetone can be ignited by heat sources too cool to be noticed in good light!)
                        I like to use the Gorilla type glue on outdoor projects I make using WR Cedar or Cypress, where I hog out half laps and want both waterproofness and gap filling. Still, I always use sufficient fasteners of the proper type, so the glue brings the joint close to bulletproof status.
                        If it seems too good to be true; <i>raise your standards.</i>


                        • #27
                          Well here's my two cents worth. I like gorilla glue, and I apply to all dadoed joints i make. face frames on cabinets, dadoed shelves in cabinets, as well as the rail and style joints too. I use a small brush, the kind you use for putting flux on copper to sweat the joint. I brush both sides just til it darkens the wood, and shines, not too heavy. haven't had oozing since doing it this way. and I had a door i made that was a quarter inch too wide. tried to tap it apart and, well it didn't happen. And I didn't wet the joint before I glued. that may reduce the oozing. not sure on that tho. good luck in your choice.