For 30 years I have applied to one surface !
I've never had a joint failure.
Remember we as guitarmakers can not compress a liquid!
Mike Collins
www.collinsguitars.com| Official Luthiers Forum! http://www-.luthiersforum.com/forum/ |
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| LMI,PVA-apply to one surface? http://www-.luthiersforum.com/forum/viewtopic.php?f=10102&t=10220 |
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| Author: | JohnAbercrombie [ Sun Jan 07, 2007 6:12 am ] |
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Another gluing question.... I was 'taught' to apply glue (all types) to both surfaces to compensate for absorption and avoid glue starvation in the joint. (This is absolutely essential when using epoxy, for example). There has been a reference to problems with LMI glue in other threads here. I'm curious whether folks here apply glue to both surfaces or only one. I noticed in the 5 Mayes videos I watched that glue was only applied to one surface, and I wonder if that could be part of the problem John reported with LMI glue. Other pics posted here show a rather heavy coat of PVA glue applied to one surface as well. So, one surface or two- what works best? What's necessary? John |
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| Author: | Mike Collins [ Sun Jan 07, 2007 8:28 am ] |
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For 30 years I have applied to one surface ! I've never had a joint failure. Remember we as guitarmakers can not compress a liquid! Mike Collins www.collinsguitars.com |
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| Author: | Mattia Valente [ Sun Jan 07, 2007 8:52 am ] |
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One here. No joint failures. |
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| Author: | Don Williams [ Sun Jan 07, 2007 9:10 am ] |
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I too was taught to apply to both surfaces. It seems to make sense that equal penetration on both pieces of wood is important. But what do I know...? |
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| Author: | JJ Donohue [ Sun Jan 07, 2007 9:20 am ] |
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With HHG, you only have time for one surface 
On other glue types such as Titebond and LMI White, I usually apply enough glue to one surface. For larger areas such as neck buildups, I apply thin coats to both mating surfaces. The rule of thumb that I use is that I want to see a slight amount of squeezeout around the perimeter of the joint. I've only been able to determine just the right amount to apply through experience. Using the above approach, I have never had a joint failure...even with LMI White older than 6 months. Surface prep and clean surfaces are as important as the amount and type of glue used. |
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| Author: | Colin S [ Sun Jan 07, 2007 9:33 am ] |
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As soon as you put the two surfaces together you have glue on both surfaces, especially if you slightly rub them to get a good seating. So, the glue just goes on one surface. Colin |
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| Author: | Don Williams [ Sun Jan 07, 2007 9:33 am ] |
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Great points about the prep JJ... |
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| Author: | Serge Poirier [ Sun Jan 07, 2007 2:41 pm ] |
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As JJ said, 2 surfaces with good ol carpenter's glue and only one with HHG because of the short open time. |
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| Author: | JohnAbercrombie [ Sun Jan 07, 2007 2:57 pm ] |
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Thanks, guys. Interesting stuff. I think the idea of spreading on both surfaces is that the first surface will tend to absorb some components of the glue more quickly than others, so that the 'leftover' glue which we are depending on to wet the second surface has reduced wetting ability. Obviously it's not essential, judging by some experiences here! John |
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| Author: | Steve Saville [ Mon Jan 08, 2007 2:52 am ] |
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I was taught to do both surfaces also. When I do just one surface, I always move it around to spread the glue onto the other side and I always peel back the joint to make sure that the glue has been evenly applied to the new side. You'd be surprised how often the new surface is not evenly covered with glue. In fact many times, there is less than 50% transfer. This is done before clamping, and may or may not indicate what occurs during/after clamping, but I'm not going to take any chances. |
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| Author: | Serge Poirier [ Mon Jan 08, 2007 4:56 am ] |
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Fish glue would then make a lot of sense for glueing plates to rims, the open time allowing to spread the glue on both surfaces. |
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| Author: | Barry Daniels [ Mon Jan 08, 2007 5:35 am ] |
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Todd, I did some testing in my shop on the effects of gluing a wood surface that has been dampened with water and the results showed that the glue joint was seriously weakened. Just thought I'd let you know. |
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| Author: | David Collins [ Mon Jan 08, 2007 5:54 am ] |
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The only time I coat both surfaces is when I am doing a two step procedure with epoxy. In this case both surfaces should be wet with mixed resin/ hardener, followed by coating one of the surfaces with a mixture thickened with a filler. I would worry that if you are applying glue to both surfaces you could be using more glue than you will need and ending up with a layer of adhesive between the two surfaces rather than solid wood/wood contact. I suppose if you clamp with enough pressure you could squeeze out enough excess, but I try not to apply more glue than needed. |
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| Author: | JohnAbercrombie [ Mon Jan 08, 2007 6:12 am ] |
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BTW, there is an excellent article by Lawrence Brown in the GAL Big Red Book One (pg 162) which discusses gluing issues in great detail. Well worth a read, it discusses issues like rel humidity and temp when gluing with PVA. Brown , like JJ, points out the importance of surface preparation when using hide or PVA-type glues. Thanks for all your input. John |
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| Author: | Serge Poirier [ Mon Jan 08, 2007 9:58 am ] |
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David, you raise an excellent point that i forgot to mention, thanks! I do squeeze both surfaces with good pressure and cauls not to damage the pieces being glued and enough to be able to clean off the excess of glue afterwards. |
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| Author: | John Mayes [ Mon Jan 08, 2007 3:43 pm ] |
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[QUOTE=JohnAbercrombie] I noticed in the 5 Mayes videos I watched that glue was only applied to one surface, and I wonder if that could be part of the problem John reported with LMI glue.[/QUOTE] I've never used LMI glue for neck blank glue-up, and I've never had a problem with neck Lams. In fact I've never had a problem with glue joints period...except when I used LMI's glue, and one time that I glued a bridge on stupid like.. when I glue something together if I only put glue on one side I rub the two pieces together which, in essence, puts glue on the other surface as well. Never had a problem. So when you glue a back to the rim do you spread glue on the lining as well as the edge of the back plate? |
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| Author: | JohnAbercrombie [ Mon Jan 08, 2007 6:05 pm ] |
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[QUOTE=John Mayes] So when you glue a back to the rim do you spread glue on the lining as well as the edge of the back plate?[/QUOTE] Yes. However, I try to put a thinner film on each surface rather than a thicker film on one surface. Apparently either will work fine. With rim/plates (it's been a while) or any large surface I find I have to be well organized. Having the glue spout cut to the right size helps. I also use a plastic body filler squeegee to spread glue at times. Solid linings make it easier to be neat as well. Obviously there are many 'correct' techniques. John |
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| Author: | JJ Donohue [ Mon Jan 08, 2007 9:26 pm ] |
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A little off topic but: One other technique I've found useful with bridge HHG gluing...I remove the lacquer or shellac with a router (very carefully). I then brush a very small amount of diluted HHG "sizing" to that surface to seal the dry, porous wood and let it sit for no more than 5 minutes before applying the normal HHG to the bridge and then clamp. I did some quick testing and found this bond to be more tenacious than just using the HHG without the sizing step. I use the same technique when gluing kerfed linings and also when gluing on backs and tops. This may change when I begin using fish glue for the top and back glueups. |
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| Author: | Dave Rector [ Tue Jan 09, 2007 4:29 am ] |
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Nice tip JJ, thanks! |
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| Author: | JohnAbercrombie [ Tue Jan 09, 2007 5:11 am ] |
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Thanks, JJ...and everybody else as well. Lots of interesting comments. John |
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