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Thread: I must've done something wrong......

  1. #1
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    Default I must've done something wrong......

    I've seen it mentioned several times in the past on this forum that a good use of outdated Titebond is to paint surfaces with a diluted mixture to prevent other glue from adhering to the surface. So I decided to give it a try when I started making a new jig for laminating solid linings. I did a test first to be sure I knew what I was doing.

    I applied a diluted solution (approx. 2:1, TB:water) to a scrap piece & waited an hour or so to be sure it was dry. Then I spread non-diluted TB on a small block & pressed it onto the first piece; no clamps. After 30 min. or so I tried to pull the block off the test surface but could not. It took a surprising amount of force with a hammer to knock the block off. My conclusion was that I must've done something wrong: maybe the original diluted application needed to dry longer; perhaps multiple applications of the diluted solution were needed.

    So I began a second test. To another scrap piece I applied 3 coats of the diluted TB solution, waiting for each coat to dry thoroughly before applying another coat. I set this aside for 2 days to insure thorough curing. Again I spread undiluted TB on a small block & pressed it onto the prepared surface & left it to dry for 30 min. or so. Once again it took a significant hammer blow to remove the block. When the block finally came off, It pulled up wood from the surface of the other piece. The block came up with the TB applied directly to it as well as the 3 diluted coats on the prepared surface & wood from the prepared surface.

    Can any one shed any light on this situation? TB is not supposed to adhere (cohere?) to dried TB, but it seems that it did in this case.

    -Earl

  2. #2

    Default Re: I must've done something wrong......

    I've not heard of using Titebond as a sort-of mask before. The rule that I understand is that wood glue does not adhere "as well" to existing glue as it does to a clean joint. The general thought here is that an uncleaned joint will be less strong -- but not weak. I can see a joint failing prematurely. I believe that hide glue strength is severely compromised if the joint is not clean. Shelf life of Titebond is something that should be considered as unpredictable as it relates to its ability to function. I've never considered it and have never had a problem with it certain that some of the Titebond I've used was quite old. I only came across mentions of Titebond shelf life on this forum and am now paying a little attention to it.

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    Registered User sunburst's Avatar
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    Default Re: I must've done something wrong......

    Quote Originally Posted by Earl View Post
    ...TB is not supposed to adhere (cohere?) to dried TB, but it seems that it did in this case...
    It will in nearly any case. The warnings that we get saying that new TB will not stick to old TB just mean that we don't get as good a glue joint if we don't clean the old TB off completely. We still get a glue joint of some quality.
    Fact is, a freshly prepared surface is a much better glue surface than a surface that has been exposed to the air for a long time. It might be that the reputation of TB not sticking to old glue partly results from people's experience of trying to regluing old failed glue joints without refreshing the surface. If some, but not all of the old glue is removed, at least there is a fresh surface so the joint is better than if no cleaning was done. Perhaps we would be better warned that glue does not stick well to old, long exposed surfaces rather than being warned that new glue doesn't stick well to dried glue.

    When I worked at a cabinet shop way back in the last century, we had a policy of "pre-gluing" all end grain joints and plywood edge joints. That meant that we applied some dilute Titebond and let it dry before making the joint with fresh glue. That was to seal the end grain and avoid too much of the glue soaking into the end grain and starving the joint. In fact, an end grain glue joint has very little strength even when done well, and the joints were not relied upon for structure (they had fasteners also), but the pre-glued joints that we made were of serviceable quality in use.

    EDIT
    Wrnchbnder's post was not there when I started typing so there is some redundancy because of that.
    As for hot hide glue, it does not stick well to dried Titebond (or other similar glue), but it does stick fairly well to dried hide glue. The old glue is partially re-hydrated by the new glue so there is a bond that is about as good as we can get when gluing to old glue. Still, it is best to clean the joint to the best of our ability, and in some cases we can get away with applying a little hot water to the dried glue to give it a little head start toward re-hydrating.

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    Default Re: I must've done something wrong......

    I guess I was mostly surprised because someone had suggested using the process I described on jigs & such to prevent sticking. I wish I could remember the context; perhaps I'm just mis-remembering. Are there other suggestions for preventing parts from sticking in jigs? I've used mylar tape in the past for some applications, but some shapes just don't work very well with tape.

    - Earl Tyler

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    Registered User sunburst's Avatar
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    Default Re: I must've done something wrong......

    Shellac, lacquer, other finish material will keep most glues from sticking strongly. (CA will stick to most of them.)

    To the casual observer, the finished jigs and fixtures that we see in some luthier's shops may seem like a little too much attention to detail (even the jigs are finished!), but it just may be that the finish was applied to keep glue from sticking.

    I save the stuff that peels off of self adhesive things (like bumper stickers, pick guards, etc.) and place scraps of it between the jig and the glue joint, cover clamping cauls with it and so forth. It's a bit fiddly to do, but it works.

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    Default Re: I must've done something wrong......

    Varnish of some kind, like Minwax or other waterborne or oil-based polys, then wiped down with paste wax is a good way to go.

    The best thing to do is to make sure your part is as smooth as possible before you apply something to make it nonstick. Even with the slickest stuff, most glues will form a velcro-like mechanical bond even if they're not bonding well to the underlying surface. The slick tape John mentions is a good idea, but I usually just wax up my forms and go for it. Or use HDPE to make your forms... nothing sticks to that stuff.

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    The Amateur Mandolinist Mark Gunter's Avatar
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    Default Re: I must've done something wrong......

    In general, Titebond squeeze out and/or glue runs that are not under clamping pressure will not adhere well to any sealed surface. But under a little clamping pressure, adherence will be improved, as you have experienced. In fact, under clamping pressure, it can adhere even to wax paper to some extent.

    To answer your “polling” question, I use wax paper, or tape lubricated with burn-in balm, or just burn-in balm alone when tape is not sensible. An example would be for a flat caul, my preference is a finished surface on the caul, covered evenly with masking tape, and coated lightly with burn-in balm.

    On rare occasions when burn-in balm is not at hand, in a pinch, I have used any lubricant available including WD40 or even furniture polish. The key is to prevent contamination as well as possible and to clean up surface to remove any lubricant contamination. Burn-in balm cleans up easily with naphtha or lacquer thinner and at any rate has never caused problems for me with discoloration or finish adherence. YMMV
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    Default Re: I must've done something wrong......

    I have used paste wax in the past for some jigs. My biggest concern here is that wax or something similar might seep into the wood & compromise subsequent glue joints. Since the current jig is for linings, & the side to be glued to the rims will be against the jig, I want to be careful to avoid any contamination. Do you think that residual wax or burn-in balm could be sufficiently removed with solvent to avoid any future glue joint problems?

    Thanks - Earl Tyler

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    The Amateur Mandolinist Mark Gunter's Avatar
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    Default Re: I must've done something wrong......

    I’ve used it for decades on finished surfaces (doing burn-ins) and when I feel it necessary or useful on unfinished surfaces (doing glue ups) with no problem of finish adherence afterward. I’m usually not coming back with more glue, but often coming back to finish, or spot finish.

    I believe it’s easier to neutralize contamination with that burn-in balm paste than with wax, but I’ve used wax or waxy products in a pinch. The key is to be careful to limit contamination, and to neutralize any potential contamination as well as possible with an appropriate solvent, I think. But I’m speaking of professional wood finishing in general, and not lutherie-specific tasks or details.
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