I have a 1954 Gibson J160E in for work. This is the first year of issue for the J160E, it's an interesting piece.

The top and back are glued on with a glue I have not run into yet. It is foam like and present all the way around the perimeter of the top and back. I collected some and it is full of bubbles like an expanding foam insulation. It is fragile and crumbles easily. I tried heating in water for 10 minutes at 160 degrees with no effect. I soaked it in lacquer thinner for 10 minutes, also with no effect. The braces appear to be glued with a White glue(Elmer's?), definitely not the same adhesive.

What is this stuff?

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Is it possible that drying conditions could have caused this, perhaps a chemical reaction to something previously on the brush used to apply the glue? I have also seen something similar to this, but the guitar was a late 90's model and I assumed that gorilla glue was used since it bubbles and expands while drying. I am not saying your guitar has gorilla glue since I do not believe the manufacturer is very old......I really hate gorilla glue. Sorry I was no help, but I felt the need to rant.
Maybe it's been re-glued?
Looks somewhat like the glue used on a not dated Suzuki accoustic (owner says he bought it in Amsterdam end of 60/ beginning of 70’s). Heat and/ or moisture didn’t do anything with it, but my “sharper that a pizza-knife” spatula just cut through like it was butter. Cleanup was easy, but I still have no idea what glue (if any) it is/was...
Pierre, the glue is present around the perimeter of both the top and back. It seems unlikely that it would have been disassembled to that degree.

Whoa Bart, what an ugly mess! Your glue mess seems much more runny than the stuff in the J160 but the color and properties are similar. I heated some of this stuff on a soldering iron and it took a while but it finally started to bubble and then turn Black. It did not have much odor when it burned, I was expecting maybe a chemical smell.
It looks like Polyu Insalation to me . I have seen some odd typs of materal used on some stuff coming out of China I worked on a Resonator Guitar a wyle back and the neck was glued on with some kind of siramic .So don't be surpised what you see today. Bill."""""""""""""
I am not sure about the 50's but in the very early 70's I was in the Gibson factory (still in Kalamazoo) and they were using a glue which was cured with a radio frequency device - basically I think it acted by heating the glue. My recall, however, is that this glue was darker. Just a thought.
I just did a bit of digging around and found a reference to Phenol Formaldehyde radio cured glue at the My Les Paul Forums. A contributor stated that all 50's Les Paul models used Phenol Formaldehyde to glue the Maple tops on and that it was cured with radio waves. First year of issue for the Les Paul Standard was 1952. It appears as though they where experimenting with this adhesive a few years prior to the fist year of issue of the j160e. I'm guessing that is what the glue in question is on the J160e I have. As to the color of the PF adhesive, maybe there was some ability to manipulate it? I emailed Gibson last week but I'm still waiting for a response on this.
I remember this glue from repairs I did on Gibson acoustics in the 80's. I believe it is some kind of phenol-formaldehyde, and the bubbly texture certainly suggests an accelerated curing by radio frequency induction, using the water content of the raw glue as the electrical conductor. I seem to remember the same kind of glue did a p*ss-poor job of securing the neck on some SG electric models.
Charlie mentions the radio-cured glue – this was only used at Gibson in that 70’s period for a brief time, and the reason it was a brief period is because they discovered that the braces that were zapped showed very dark right through the spruce tops after about 6 months. They were in go-back h*ll, as so many of their guitars advertised their bracing patterns from across the room, as the stain of the glue bled through the spruce.

Paul Breen came across and repeated some misinformation acquired on his Les Paul Forum. Les Paul tops were glued to the mahogany bodies with heated hide glue. This fact emerged when Dana Bourgeois, during his tenure working with Paul Reed Smith, was assigned the task of discovering the real difference between the early Les Pauls and the revived run that began in the late 60’s. The early ones had been glued with heated hide, and the later ones were done with aliphatic glue, which Dana discovered functioned more as a rubber gasket, while the earlier glue was sonically transparent.

The bubbly-looking dried glue is Weldwood Plastic Resin Glue, a very irreversible pre-catalyzed urea-formaldehyde glue that’s made by mixing a powder with water. It is not cured with electricity, it just kicks after adding water because it contains barium chloride. It was a favorite of boatbuilders for laminating masts and the like, and came out in the very early 50’s. It’s entirely possible that Gibson experimented with it in the early 50’s, but it was not the norm, and it was definitely not what they glued Les Pauls together with.

Thanks to its composition, Weldwood Plastic Resin Glue does foam a bit when it kicks after adding the water, and emits formaldehyde fumes as it does so. Ghastly stuff.
Interesting find on the '54 J160. I remember in the mid 70's lusting over a New J45 in a music store. It was supposedly reduced in price because of what was then called 'bracing shadow' showing thru the top. I had since learned as Paul stated that it was an experimental glue issue that had gone awry..Ha! If my memory serves me, they were asking $400 or so for that guitar. Whatever the price, it was a king's ransom for 20 year old. I have also since learned that 70's Gibson were not up to par with other eras.
Thanks Paul for demystifying this issue. : - )

I did find out over at the MIMF that it must be Urea Formaldehyde but the assumption was still that it had been cured electronically.
Apropos, I just got a really juicy LG-3 in this week, I haven't referenced the FON yet but it's just post-Banner, ca. 1950, with lots of that WPR squeezeout. Numerous joint failures, fortunately nothing too grave. When the glue is rock hard and the wood on either side of the seam needs to move, it's just not the ticket. Glad they didn't do that very much!


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