Bending Purflng

[Kevin Sjostrand]

One thing that can happen with " the wedge clamp" idea is you may not get even pressure on you pieces as you slide them into the wedge. Any variation in thicknesses of the materials or even if the boards you're using for clamps are not perfectly flat......you may have spots that are not as tight when clamping which can account for areas not as well glued or as tight a fit.
I've found that out the hard way.
So this is why I just use a series of clothes pins to pre-attach the purfling to the binding. You can see how things are clamped BEFORE applying the CA and adjust as needed.
Anyway sounds like the Gorilla glue worked well for you so do what is best for your situation. The end result is what matters!

[scamp]

Kevin

You raise a good point. When I made my ramp/clamp jig it took a lot of effort to get the two clamping surfaces dead flat as I knew if they weren’t I would have a problem. I also took extra effort to get the bindings and perflings exactly the same thickness using a drum sander and perfling planer jig I built. In the end it worked well but I can definitely see how it’s easy for it to have problems. I like the idea of clothes pins and CA glue but I just can’t get the joint to look as good for some reason. I suspect it would look fine with the CA glue method if there was more contrast between the binding and purfling woods ( as there usually is) which would tend to hide any slight issues in the joint.

[scamp]

Did a few more experiments taking into account the feedback I received. Thought I would pass on the results.

One was to use clear Gorilla glue, but this time with just the clamps ( similar to clothespins ) I use to glue the kerfing. This way I avoid the problems mentioned by Kevin with my ramp/clamp jig arrangement. Unlike CA glue, the Gorilla glue takes about 2 hours to set up before you can remove the clamps but it wasn't a problem and it worked like a charm. Much easier than building the jig etc with probably more reliable results. Thanks Kevin.

The other experiment was inspired by something John Hall mentioned in one of his videos about using super glue to join the back of rosewood guitars. He mentioned that it wasn't a good idea to use this method with porous woods like mahogany and walnut ( which were exactly what I was using in my previous binding/purfling glue experiments . So... to see why the warning, I put some CA glue on a scrap piece of mahogany, let it dry, and then scraped it down and sanded it a bit and compared it to an identical piece of mahogany I scraped and sanded identically without the CA glue. Low and behold, there were visible dark areas in the grain of the mahogany with the CA glue sample. You could get rid of them but you needed to sand down quite far before they went away. Further than in some cases you would want to.

So.. I think I will stick with the Gorrilla glue for now with clamps and be very careful when using CA glue on anything slightly porous like mahogany etc. Also, I think I would be very careful about using CA glue to glue any bindings to guitars with mahogany sides. My guess is that sealing the mahogany with shellac probably helps a lot. Yet another experiment to run...

Just an FYI.

[Stray Feathers]

This thread has been helpful in several ways. But I am interested in alternative glues. Given the known problems with CA staining some wood, I may try the Gorilla clear. Does anyone know what family of glues it fits in? How un-gluable it is? Whether you can load it with coloured sawdust as a bit of filler? Is it water cleanup or something else? Thanks - Bruce W.

[scamp]

All good questions but I'm afraid I don't have a lot of good answers.

I do know that unlike standard Gorilla glue, this formula doesn't foam and hence is more usable for guitar work and won't create gaps etc. They also mention that like CA glue, moisture is required to make the glue cure and it helps to dampen the surfaces.

Jeff Jewitt mentions in some videos he posted that he also uses this glue to glue in rosettes on his guitars.
He also told me in an email that he uses this glue to make his purfling by gluing together different colored veneers and then pressing them together in a vacuum bag.
The big selling point of the glue is that it doesn't stain the wood, can better handle high temps for bending, and since it isn't water based it won't warp the wood ( thin veneers ) like Titebond original.
Since it has these propertied I suspect it could also be used to glue in the bindings ( like John Hall uses Duco Cement) but I haven't seen anyone do this yet.

As far as ungluing, I know it is water proof and they say it holds up to 90 degrees C or 194 degrees F. I know water won't clean it up. Just need to wipe it with a dry cloth and sand/scrape it off later after it cures. Also.. given what I have experienced using it, it doesn't seem to have the consistency that would be conducive to adding filler/dust etc. I don't think it would be good for that purpose like CA glue but not sure.

Would love to hear if anyone else has any feedback on this.

[Kevin Sjostrand]

I've not had the CA stain any wood. If you use CA on spruce with exposed end grain....such as a binding channel with a spruce top....just wipe or brush some shellac on that exposed surface so the CA will not go into the wood. Simple as that. I've not had issue with maple or walnut or rosewood or ebony binding, or fiber purflings staining.

[Kevin Sjostrand]

On the Gorilla glue. I believe original Gorilla glue is a urethane glue. The non foaming may also be. I imagine this can be looked up but if it's not water soluble I'm thinking it may also be a urethane glue.

[scamp]

Kevin

I believe you may be right about the Clear Gorilla glue being a urethane glue but I looked on the web and can’t find any info on it. The catalyst reaction in the standard Gorilla glue causes CO2 to be released and hence the foaming. Since the Clear doesn’t foam I’m not sure if it’s the same. That said , Clear Gorrilla glue needs moisture to cure, the same as standard Gorrilla glue.

As far as CA causing staining, I can see a difference between CA and the Clear Gorilla glue on Mahogany but it’s relatively minor. It appears to me that the CA glue fills the pores in the Mahogany and it makes the wood darker. If you sand it down deeper than the depth of the pore it goes away. Also, I suspect when you finish the wood it darkens all of it and you can’t see it. As a test I used naphtha on the Mahogany with CA glue and the little dark areas in the pores couldn’t be seen because the rest of the wood was now just as dark.

And a question. What do you use to seal the spruce to keep it from staining. Standard off the shelf shellac or do you dilute it with alcohol?

[Kevin Sjostrand]

You're right about the darkening on the wood. Once you apply your finish the whole surface will darken.

I have mixed shellac flakes for one French polish finish on a classical guitar. But I used Zinsser Seal Coat to actually French polish two other guitars with satisfactory results.

SEAL COAT is pure shellac at I believe a 3lb cut....maybe 2lb. Can't remember. No wax. Thin with alcohol. I don't have access here in California to near pure distilled grain alcohol so I use denatured from the hardware store. It seems to work okay. They actually are now not allowing denatured alcohol to be sold in Cali. I bought 4 gallons of it from out of state so I'd have a supply for awhile.

The Zinsser Shellac in the can has wax in it so you don't want to use that.

Shellac works great for a sealer.

[scamp]

Thanks Kevin. I’ve been assuming the Zinsser’s Seal Coat Shellac is 2 lb cut. I have previously mixed it with ethyl alcohol to get a 1 lb cut for sealing the back and sides before applying the filler. I assume a 1 lb cut like this would be a good consistency for sealing the binding channel before applying the CA glue. Seems like you would want to thin it out to this level to get it to soak into the end grain of the spruce.