Plastic Explosives

Here's a Trini Lopez Deluxe that spent way too much time in its case. I'm guessing that guard will fall apart if you touch it.

The plastic that was used on some older Gibsons is downright dangerous. It is essentially a solid explosive that’s been stabilized. The trouble is that it doesn’t always stay that way. It’s a process called off gassing. Also called out gassing and gassing off. And it’s as bad as it sounds. As it turns out, the plastics that were used for certain components back in the 50s and 60s were not terribly stable from a chemical standpoint. Disclaimer: Don’t know much about chemistry. That said, it’s pretty straightforward. I’ve written about shrunken tuner tips and most of you have seen them but that isn’t all. Have you ever seen a 355 with the pickguard completely disintegrated and all the gold parts corroded and green? It’s not a pretty sight and it’s not something that you can simply wipe away like tarnish. This stuff actually eats the metal and plastic parts. This comes from a site called “The Museum of Jurassic Technology”

In 1868 John Wesley Hyatt formed a substance from a homogeneous colloidal dispersion of nitric acid, sulphuric acid, cotton fibers, and camphor. It was a substance of great tensile strength capable of resisting the effects of water, oils, and even diluted acids. Hyatt’s brother called it celluloid, and it became the first commercially successful synthetic plastic. It was cost-effective to manufacture and could be produced in a variety of attractive colors. Heated until soft and molded into shapes, it became a substitute for products fashioned out of ivory, tortoiseshell, and horn. Perhaps it is best known for its use in motion-picture film, where its volatility has resulted in the destruction of a vast percentage of early footage. But it was also used to fashion removable collars, collar stays, knife handles, guitar picks, piano keys, billiard balls, and, of course, dice.
Also pickguards and other plastic guitar components. The problem actually has a couple of components. The first problem is the disintegration of the plastic itself. But the real destruction comes from the gasses that the process of disintegration emits. If the guitar is stored on a guitar stand or a wall hanger, the gasses pretty much dissipate harmlessly into the air. The problem is that most guitars are stored in the case with the lid shut tight. Sometimes for decades without being opened. So what is this stuff? Well, apparently, it’s nitric acid. If you remember high school chemistry, nitric acid was one of the things the teacher didn’t let you use in the lab without a bunch of protective gear like heavy rubber gloves, goggles and stainless steel tools. They probably don’t let students anywhere near it anymore in these politically correct times. Nitric acid will eat the hardware-including the frets-of a guitar that’s in the case with an off gassing pickguard. It will also damage the nitrocellulose lacquer (which is chemically similar) finish. The cautionary tale here is that if you’re a collector who stores his guitars and rarely plays them, you might want to open the case once in a while and let the gasses out. I’ve read that celluloid can be completely stable for decades and, suddenly, completely come apart chemically over a very short period (like weeks). It doesn’t warn you either. It’s more like a time bomb that doesn’t have a countdown. Yikes.

These tuners are also an example of off gassing. These were on my red 59 ES-345 and for some quirky reason, only 5 of them shrunk. I don't think the tuner tips are celluloid but gassing off isn't limited to celluloid. Almost any plastic can gas off. Some do serious damage and others don't. Want more info? Call a chemist.

9 Responses to “Plastic Explosives”

  1. Rab says:

    Charlie, OUCH, that Trini is the nastiest example of off-gassing I’ve ever seen. I am so fortunate the guard on my ’63 355 is ok (gulp, so far!)

  2. Erwin says:

    Hello Charlie, can you do some blogs on the most impotant par of the 335’s.?: wood !!

    Like: Origins (where did the cut the trees), transport (did they ‘water’ the wood), drying methods, milling process, quality control etc
    Different kinds of maple. When did the use basswood or poplar for laminates etc Difference in tonal quality. idem rosewood and ebony?
    The cut-out in the maple centre block is it for wiring?

    greetings Erwin

  3. OK Guitars says:

    It would have to be somewhat speculative since no one seems to have good answers to some of the questions you ask. Much of what I know, I’ve learned by studying the guitars I’ve had in hand. Unfortunately, you can’t tell much about the wood unless you know something about it-like how to tell poplar from basswood). So, some research will be required. Things like the drying methods and milling process would have to be learned from someone who was there-and they are pretty hard to find these days. I can tell you that cutout in the center block was done to make it easier to get the harness installed. The uncut center block (335 and very early mono 355) required the harness to be installed through the f-hole which is a fiddly procedure. The stereo guitars always had the cutout for the Varitone choke and ease of installation as the switch wouldn’t fit through the f-holes. I’ve done a post about the fingerboard woods although I didn’t talk much about the source of the ebony. The mahogany used for the necks is worth pursuing as well as a post-not to mention the sawing procedures like quartersawn and flatsawn and all the others.

  4. OK Guitars says:

    Hey Roger-Just don’t leave it in the case unopened for more than a few weeks at a time and you have nothing worry about. Apparently it can happen very quickly once the plastic starts breaking down. It also depends on how well cured the original plastic was. If done properly, it may never break down. Or you could drill a couple of big holes in the top of the case and put in a couple of battery powered fans. That’ll take care of it 🙂

  5. RAB says:

    Thanks Charlie, getting out the Sawzall now! Ha, ha!…

  6. Paul S says:

    Great post Charlie, about a subject not often discussed. I had the displeasure of opening up a case with a 60’s L-5 CES and seeing little granules of…something, I wasn’t sure. Put it back in the case, and didn’t play it for a few weeks, opened it up and the guard was crumbled, and the neck pickup cover was green.

    Got the guard replaced finally, but then found that the neck pickup–a PAF by the way–was also damaged by the gas, and that only one coil was still functioning!

    So this outgassing can not only ruin the pickguard and tarnish metal, it actually eats pickups! BEWARE.

  7. OK Guitars says:

    It will eat the windings-no question. If you’ve ever handled pickup wire, you know how fine it is. It doesn’t take much to damage it. A little nitric acid goes a long way.

  8. Adam Fingrut says:

    I recently discovered a similar problem with a 1978 Ibanez that was left in the case for a few years. The super 80s are completely green – wondering if i’m going to have to scrap them and find some replacements…or if the damage is only cosmetic and I can get the guards re-plated…

  9. okguitars says:

    You can have any metal parts re-plated if the base metal has not been badly pitted from the chemical reaction.
    I’ve had pickup covers re-plated after “off gassing” has occurred.

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