The list has been pretty quiet of late, and although I realize the following is quite off-topic, I thought many of you might be interested in taking a stab at what has for many years been an 'unexplained phenomenon' I witnessed.
I am not a glass conservator per se, I am a scientific glassblower. About ten years ago I had a commission to fabricate a number of quartz glass spectroscopy cuvettes. I made them from 30 mm lengths of rectangular-bore stock tubing (3x7 mm ID, 0.9 mm wall), closed at the bottom, and with a 10 cm length of 7 mm standard-wall round quartz glass tubing fused to the top. They looked like little glass rowing oars. My customer didn't need them all at once, so many of them were assembled from pieces that had been prepared and left in a box for some weeks.
In working quartz glass a white crusty deposit called 'bloom' will condense on the glass adjacent to the working point, and standard procedure is to 'burn' it back into the glass by direct application of flame (with a hydrogen/oxygen fueled torch). It was during this last procedure, when the entire rectangular section of the cuvette is brought to a white heat (>>1000 C), that most of the first batch of cuvettes I made would 'sing'! It was a 'pure' tone (approximately G over middle C), and about as loud as a normal speaking voice. The sound reminded me very much of a 'glass harmonica' or 'musical wine glasses' . Holding the finished piece by the end of the tubulated neck, I could feel it vibrating intensely.
Immediately upon removing the flame the singing would diminish, but persisted approximately for as long as the glass was 'glowing hot'. About 75% of the cuvettes sang, which I found puzzling until I noted that if the cuvette was moist from rinsing with distilled water it always sang, and if dried in a drying oven it never sang. The phenomenon would persist for as long as heat was applied, although I never extended this for more than about 15 seconds out of concern for deforming the walls of an otherwise servicable cuvette that someone had paid for :]
I've always wondered what caused these cuvettes to sing? I've worked with many similarly constructed quartz and pyrex cuvettes of different dimensions, and none of them sang. Obviously, water is somehow involved, and my guess is that it has something to do with its rapid sorption/desorption from the inner walls causing some sort of organ pipe standing wave, although it could be far more complex (such as the dissociation/re-association of the water molecules).
Any input would be greatly appreciated.
Last edited 02-18-03