repairing nuts with the CA trick and ... alabaster powder?

[RJVB]

A while back I converted a small, (probably calcite) alabaster ashtray into a candle holder, grinding it out until it held tealights. I kept the very fine powder but haven't yet dared to use it.

I'm sure it'll behave the same way as bone dust in terms of forming some sort of resin, but how resistant and/or abrasive (for nylon strings) would it be. Anyone an idea?

[wintermoon]

as long as it's smooth you'll be fine

[Freeman Keller]

I do the CA/bone dust trick for a quick fix if for some reason the nut slot is too low (I wouldn't have done that on purpose, would I?) but I always make a new nut when I get the time. If I'm working on my guitar I want it done right, if I'm working on someone else's they deserve it.

[RJVB]

Oh, I'm doing them right alright - it's very hard to see when I redid a slot

That's actually another reason why I haven't yet used the alabaster powder: it's got some residu from the dremel grinding bit I used in it so it would probably not be as good a match to bone as the baking soda I use normally.

[sgosnell]

I think the chemical reaction of the cyanoacrylate with sodium bicarbonate creates a stronger material than cyanoacrylate alone, or cyanoacrylate mixed with bone, or other fine dust. I don't know of a reaction between cyanoacrylate and alabaster, but I haven't researched it. Without an actual chemical reaction it would seem to create a somewhat softer result than other materials, because alabaster isn't very hard itself, and mixing a soft material into the matrix would seem to result in a softer material than CA alone. Baking soda, OTOH, creates longer polymer chains than CA alone, thus a more durable material. I suppose bone dust in the matrix could give something stronger than CA alone, but it would depend on the mixing, and would require thorough mixing of the CA and the dust, which is difficult to attain. Baking soda doesn't have to be thoroughly mixed in, though.

[RJVB]

I think the chemical reaction of the cyanoacrylate with sodium bicarbonate [...] Baking soda, OTOH, creates longer polymer chains than CA alone, thus a more durable material.

Do you have proof of that, or do you just think that?

I don't know what the liquid in CA is, but I always supposed that bicarbonate could dissolve in it, or the liquid penetrate somewhat into the bicarbonate crystals (i.e. a physical process rather than chemical reaction). That would also create a harder or at least glassier material, and it certainly seems to be the case that you don't find the granular structure of a pile of sodium bicarb. crystals after the solidification with CA. I like to think I help that by packing the soda into the slot I'm filling, both before and after I add the CA.

Then again the end result could also be softer. If you assume bone dust consists of tiny balls there is a lot of empty space to be filled with liquid enough CA which will then hold those particles together but have a resistance to compression that's higher than of some sort of gellified baking soda.
I agree that alabaster isn't very hard, but if bicarbonate can have an actual chemical reaction with CA then maybe so can calcite...

I suppose one could look at how easily either mixture develops an imprint of the winding of a heavy string.

[nevershouldhavesoldit]

I don't know what the liquid in CA is

I think liquid cyanoacrylate is the pure monomer - there is no solvent. Water causes it to polymerize (I.e. “set”), so it can’t be in an aqueous base. Acetone, many alcohols, and similar organic solvents will break down and dissolve polymerized CA.

Bicarb combines with the CA monomer and triggers rapid polymerization into longer chains than those that form when allowed to set from moisture in the air. This long chain polymer is harder than that formed from letting CA set on its own.

[RJVB]

It's not just water that causes CA to polymerise of course; contact also does (in Dutch it's known as "contact glue"). So I guess there's still the possibility that any fine powder acts as a sort of catalyst to trigger polymerisztion into longer chains.

No, I'm not trying to be right here, just rigorous

EDIT: if CA is a pure monomer that doesn't contain a solvent (in itself that does make some sense), how do you explain it exists with different viscosity levels?

[RJVB]

Acetone, many alcohols, and similar organic solvents will break down and dissolve polymerized CA.

I knew about ammonia (IIRC...), not any of the others. Rubbing alcohol may or may not slow down the polymerisation if e.g. I want to clean the nozzle of a bottle of CA, but nothing I've tried has helped to clean dried CA from those fine screw-on applicators I have. So nowadays I just use a vulgar toothpick to transfer a drop of just the right size.

Anyway, is there a solvent that should dissolve CA without attacking a nitro finish? My archtop has a "gunk spot" just under the fingerrest brace where someone must have spilled CA and then tried to whisk it off (which evidently just increased the size of the spot). I've used one of those 3-grade nailbuffing thingies to buff some of it off and make the rest as close to "shiny transparent invisible" as possible but wouldn't mind getting it off completely.

It's not something I did, nor do I know the story so I can't really see it as part of the instrument's history.

[wintermoon]

I knew about ammonia (IIRC...), not any of the others. Rubbing alcohol may or may not slow down the polymerisation if e.g. I want to clean the nozzle of a bottle of CA, but nothing I've tried has helped to clean dried CA from those fine screw-on applicators I have. So nowadays I just use a vulgar toothpick to transfer a drop of just the right size.

Anyway, is there a solvent that should dissolve CA without attacking a nitro finish? My archtop has a "gunk spot" just under the fingerrest brace where someone must have spilled CA and then tried to whisk it off (which evidently just increased the size of the spot). I've used one of those 3-grade nailbuffing thingies to buff some of it off and make the rest as close to "shiny transparent invisible" as possible but wouldn't mind getting it off completely.

It's not something I did, nor do I know the story so I can't really see it as part of the instrument's history.

You can use acetone on poly to clean off CA but I'm not aware of anything safe for nitro.

[sgosnell]

The only proof I have is what I read on the internet. A search engine returns many hits, including several that seem to be legitimate.

I don't know of anything that will dissolve CA but have no effect on nitrocellulose. I have a bottle of acetone for use in dissolving CA, but it will dissolve nitro as quickly, if not more quickly. Contact itself doesn't start the polymerization. CA sticks to fingers immediately because of the moisture in the skin. You can also speed the process by just blowing on CA, with the moisture in your breath being enough to kick it off, albeit not quite as rapidly as touching it with a finger. A specific accelerator is also available, and often used by repair professionals. I've never bothered to buy it, though.

[nevershouldhavesoldit]

EDIT: if CA is a pure monomer that doesn't contain a solvent (in itself that does make some sense), how do you explain it exists with different viscosity levels?

Methyl methacrylate, silica and alumina are commonly used additives to increase viscosity.