My student is making a musical instrument using a set of wine glasses, but he wants to mount them upside-down. So using water to adjust the pitches is out – he’ll have to use something that will stick to the glasses and change the pitch without deadening the sound. Any ideas?
I’d try pouring resin (Epoxy) in the glass and seeing how it sounded when it hardened.
Hmmm… tuning them will be tough.
Presumably you can change the pitch by cutting away glass, which sounds at least as tough.
Or you could build a big centrifuge, with him standing in the middle. This one seems really tough.
The ony thing I can think of is searching for glasses that have the right natural pitch when empty, which sounds like a long term project unless there are manufacturers who produce them.
You need to add mass, and the best place is probably going to be around the rim. Trick is that the added mass should not act to damp the energy - so using something like blue-tack will work, but probably not so well as glueing a hard mass on. Distribute the masses around the rim symmetrically. Interestingly the pattern of how the masses are added can change the overtones, and even get you multi-tones. Glueing on small lumps of metal (nuts and washers maybe) with cyano-acrilate glue would be my first guess at a useful approach.
[Quote=Boyo Jim]
Hmmm… tuning them will be tough.
[/Quote]
Would either of these two methods work?
-
tune them with water right-side-up. Mark the water line. Remove the water. Fill to the water line with epoxy. My only concern is the effect on the tone when a hardened liquid is used in place of a runny liquid.
-
use an epoxy that hardens slowly and tune the glasses right-side-up the same as you would with water
I’d think it would be more sensitive even than that. My guess is that a glass partially filled with oil would vibrate at a different pitch than one filled with water, than one filled with vinegar, etc … Maybe something to do with viscosity?
How does he intend to play them? I can’t imagine wine glasses holding up to being played as a percussion instrument, even with soft mallets.
They don’t call it chopsticks for nothing.
Thanks for the ideas. Looks like we have some experimenting to do.
The intention is to mount the glasses on the underside of a board, each next to a hanging mallet. The mallets will be pulled by strings on the top of the board. (Having the mallets hanging simplifies things.) The other reason for avoiding a liquid is just the potential mess.
Ben Franklin invented the glass harmonica where the sound varies based on the size of the glass. Water merely serves as a lubricant.
The simple solution is turn the glasses right side up and set them on a shelf under the mallets.
I would think resin would deaden the sound plus I imagine you need it several inches thick. I don’t know what kind of resin you would use. Most resins would need to be done in many many layers and take forever to setup.
A quick trial could be done using wax. It could be done in one step and setup fast. It’s cheap and plentiful, especially if you have some candles around.
I wonder what drilling a hole in it would do. But even if it did work finding the right spot sounds like a nightmare.
You would be better off cutting glass tubes to the correct length.
If the goal is to play the glasses upside down, then putting them right side up is the exact opposite of a solution.
And your centrifuge would only allow the glasses to be sideways, not upside down. But seeing how human sized centrifuges are so popular in the performing arts these days it has the advantage of being off the shelf technology.
Maybe it’s lame to tell a kid to abandon a design aesthetic because they want to use materials that are unsuitable for it. It robs them of spending all their time trying to do the impossible instead the boring usual way.
Or if the aesthetic is so important they can think of something better to use then standard wine glasses to produce notes. (tubes or bars of different length)
The centrifuge could be mounted vertically too, though the glasses would only be upside down a small part of the time. In either case, playing it would be an absolute bitch.
I have another thought that involves finding a liquid more dense than glasses and suspend them in there, so the glass would float upward. I think to hear anything, though, the audience would have to be suspended in the same liquid. 
Aquadementia, I believe you and I are in general agreement. In my first post I suggested forgetting the liquid and cutting the class down until it’s the right pitch.
I think a slow setting polyester resin (like the stuff used to encase insects and other objects in clear plastic) could be poured in glass-size volumes and would cure without any significant problems - slow set means it won’t heat up too much while curing.
With an electronic tuner and a pipette for fine tuning, it might be possible to tune them while the resin is still liquid.
Jell-O.
Also, Saran Wrap will work to keep both water or gelatin from falling out.
Paraffin.
Cheap. Readily available at the grocery store. More easily tunable.
With gelatin, you can buy non-flavored/non-colored packets, so it still looks like water.
It’ll be liquid for plenty of time for tuning. Just add double or triple the amount of gelatin as you would for a dessert, and that stuff should have no problem clinging to the glass upside down. Plus, it’s still wobbly, unlike wax or epoxy, so the quality of the sound should maintain its fidelity as if it were still water.
My guess is that this is the best bet! Plus think of the fun with lots of different colors.
I’m just going on intuition, but I’d expect goopy unset epoxy to sound duller than water. Furthermore, you’d have to get a new set of glasses after every practice or performance! Better bet is to use just the resin, but I still bet it would sound dull.
It’d be pretty easy to test out the Jello.
On further thought (and experimentation at the kitchen sink), I am inclined to agree that resin might not be a good choice.
The pitch lowers as more water is added - so I think what must be needed is something that couples intimately with the glass, but remains flexible. The flexibility of the resin is going to change as it sets, so the tuning will probably change too.
But for goblet-shaped glasses, gelatin is just going to drop out when the glass is inverted less than half full(/empty!).
I’m starting to think that Boyo Jim’s suggestion in post #3 could be the way to go. Get an electronic tuner and visit a whole load of thrift stores and test each glass until you find the notes you need (this could be a very cool way to do the project)