Professor Omen's chemically tempered glass demonstration

Tom's teacher (D. R. Uhlmann; cluster name in aggregate uses captioner mishearing "Omen") demonstrated chemically tempered glass by hand-flattening a curved 18″ × 3″ piece without breaking it. The pedagogical demonstration of ion-exchange surface compression.

Professor Uhlmann, who taught me, who was a glass expert, had a piece of glass that was about 18 inches long, three or four inches wide, and was bowed about two inches high. He could take that with his bare hand and just flatten it, just like that, and it wouldn't shatter, wouldn't break, even with that type of curvature. When he flattened it, he wasn't exceeding the compressive residual stresses that he got by putting sodium and potassium ions replacing the lithium ions. Fairly expensive, because that one piece of glass has to sit in this furnace for several days to diffuse in this ion exchange. In fact the John Hancock building has chemically tempered glass of sodium and potassium.

A piece of bowed chemically tempered glass that could be flattened by hand without breaking, demonstrating favorable compressive surface stresses. Name uncertain ("Owen" or "Omen").

Professor Owen [?] when I was a student had a piece of chemically tempered glass that had compressive residual stresses. It was bowed, it was an eighth of an inch thick, and he could put it on the table, and he could flatten it with his hand — three inches over about 15 inches — and it wouldn't break, because it had favorable compressive residual stresses. I'd love to have that sample. I'd probably wear a pair of gloves when I did it, because one day it's liable to have a defect or a scratch, and all of a sudden it's going to shatter, and cut my hand. Nonetheless, you don't want to have any residual stresses, or if you do, you want favorable residual stresses that are compressive on the surface, so you have to overcome the compressive stress when you're bending the glass.