What was I looking for in the x-rays? Well it was a bit of a rush job throwing these specimens together in minutes and heading back to the medical centre so I did not get everything I wanted. A second visit is necessary! Anyway, these were the things I wanted to investigate 1) Just to see the large bubbles in a few of the pieces and see their sphericity and whether it was one bubble or a bubble complex. 2) To view bubble complexes in breadcrusts (gatherings of small bubbles in the centre - I was sure these existed). 3) To see if asymmetrical dumbbells typically contained large bubbles in the bulbous end.
Provisionally, and it was a small database, this is what I observed. 1) Bubbles were of a size predicted for the larger specimens. These were single large bubbles, not bubble complexes. These were spherical to slightly ellipsoidal. 2) Breadcrusts did indeed appear to have bubble complexes - a number of small bubbles gathered in the centre of the specimen. Furthermore, to my surprise the larger smooth spheres did not appear to contain bubble complexes. The ones I had considered to be solid contained a single small bubble, larger than those in the bubble complexes. 3) Asymmetrical dumbbells did not appear to typically contain large bubbles in the bulbous ends, although bubble complexes were noted (which, of course, will always be more prominent in the larger bulbous end) - the bulk of the large bulbous end was glass.
The images you see below are somewhat compromised by the scan quality. The actual x-rays are of much higher quality and you can pick out subtle changes not visible here. Nonetheless they give a good idea of what I observed. Note that the photographed specimen may be in a different orientation as I forgot the camera battery when I went to the x-ray!