Official Luthiers Forum!

Yes, nitrocellulose, as in gun cotton and celluloid (binding, picks, pickguard material) and nitrocellulose lacquer. We luthier types play with all kinds of dangerous stuff!   I've seen guitars where the binding just self immolated in the case...poof, and all that's left is some ash-like substance.   One day the guitar was fine, the next day it wasn't.   Also, old celluloid movie film has been the downfall of many a movie house. The projector gets stuck, the projectionist is smooching with his or her best friend, the frame is in front of a hell of a hot bulb, and bye bye movie theatre.

Al,

I'm not familiar with what a "spark box" is, but ozone is generated by passing a high voltage arc through air or oxygen. Of course, this is what you smell after a good lightning storm. So my guess is that a "spark box" generates ozone.

Randy

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Randy Muth
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[QUOTE=Shawn]
DESCRIPTION:
Nitrous Oxide is an aesthetic gas best known for its use in dentistry and as a whipped cream propellant.
[/QUOTE]

Huh. I was under the impression it was invisible, now you're telling me it's pretty?

(sorry, couldn't resist)

Billy T asked:
"This nitrocellulose, isn't it explosive? Like gun cotton?"

Yup; guncotton is nitrocellulose.

I actually made some 'nitro' for a High School Science Fair project: that was a while ago, and certainly would _not_ be happening in a High School near you these days!

Nitro was one of the first plastics. They were trying to dissolve cotton so that they could reconstitute it into silklike threads. Somebody finally tried a mixture including nitric acid, but nothing seemed to happen with that, either, except the beaker got warm. The story I got was that he washed the cotton off, since it looked fine, put it on top of the coal stove to dry, and went out to lunch. When he got back, the lab was gone.

The early 'rayon' was nitrocellulose that was dissolved in strong organic solvents and extruded through spinarettes into water, where the solvents would be removed leaving threads. When highly nitrated it was just like silk, and was quite a fashionable fabric until one young lady's gown got touched by a gentleman's cigar at a debuttante ball in England. She died a few days later of massive burns.

After that they set limits on how much the stuff could be nitrated. It turns out that when you nitrate 18% of the cellulose molecules in the cotton it's soluble, so that's the normal limit. It's not enough to make it explosive, just really flammible, and chemically unstable over the long term. Movie film used to be made of nitrocellulose, but they stopped using it because too many theaters burned when the projectors jammed.

A high explosive is basicaly a chemical that contains both fuel and oxidizer in the same molecule, in a 'metastable' arrangement. That is, it will stay put until you 'kick' it with a little energy, and then it 'burns'. When there are enough of these molecules packed in together the energy given off by one will 'kick' the next one, or more, and the reaction goes faster and faster. In the normal nitrocellulose lacquer there is not enough explosive to do that, but eventually, given enough 'kicks' by things like sunlight, more or less all of the nitrated stuff breaks down.

When it does, it releases the nitrates that went into making it in the first place, and these are what cause metal to corrode on guitars that have been left in the case for a long time. They also can discolor the wood or other plastics, which is why nitro turns orange with age. Finally, of course, you're taking one molecule in six out of the finish, so it shrinks and checks.

So that's my rant about nitro. There's no reason why you could not nitrate the cellulose in in wood, too, with much the same long-term result. Whether that would make it stronger in the short term is hard to say. Given the number of different things that make up wood, exposure to that sort of treatment would most likely do other things as well, but I have not the chemistry to tell you what.     

   What if you added some glycerine? Would that make your playing more explosive? Actually I was wondering about an epoxy impregnation type grain sealer treatment. I had a small piece of rosewood and with some extra 30 minute epoxy from gluing a chair leg I wiped a coat on the wood, rubbing it in until I guess you'd say dry? It darkened the wood a bit and later dried completely, seeming fine. I thought this might be a nice sanding sealer or grain filler. I like the way it darkened the rosewood a bit. It seems like it might make the wood stronger, but reading these discussions I realize it might cause problems with natural oils, or wedge more cracks when expansion and contraction takes place. An elasticity seems important, though I could see how something more flexible would dampen tone. A lot of guitars sound to me like something like plastic dulls the sound. I find dry crispness of tone to be most desirable, though this certainly happens with aging too I understand.nickton38810.6453356482

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"Preoccupation with an effect gives it power and enhances the error"
from "Your Owner's Manual" by Burt Hotchkiss.

This process may be useful for one thing. At least it's getting thinking about how well we can be finishing the insides of the guitar, and what difference that might make to the sound.
I'd be interested in hearing two identically built guitars but one having the inside surfaces scraped clean, while the other having the inside surfaces left rough sanded with 60 grit paper, with poor glue joints and wood chips floating around.

I guess my point is that if we have 'good joinery' as Grit Laskin would say, the wood will speak for itself, without the need for a Josepi process, or even Giuseppi process.
Hank38811.6165856481

Hank:
There has been a lot of speculation, and an accumulation of 'folk wisdom', over the years about the effect of the inside surface finish on tone. The general take on it is that the finer the inside finish the 'brighter'. As usual, there seems to be very little real data; well controlled experiments are hard to do in this field. One can think of a few physiaclly plausible mechanisms, but, again, checking them out in the real world takes time. At this point you can believe whom you will.