Bob Rose light bulb classroom demonstration

Tom's thesis advisor would stop at Sylvania (Danvers, MA — Corning-licensed light bulb plant) before teaching 3.091, bring fresh light bulbs, throw them at the wall — they bounced. Next day same bulbs shatter. Water-vapor surface corrosion in <24 hours.

But if you go through the fracture toughness of this glass, go back to the Ashby plot and look where the glasses are in terms of fracture toughness and calculate the minimum flaw size — it's like 10⁻⁴ millimeters. We're talking angstroms of critical flaw size, or tens of angstroms. You don't have to have very much corrosion. Just the humidity in there. Now, I've never seen this, but my thesis advisor, Bob Rose, used to do it. He still lives up on the North Shore. Sylvania up in Danvers has a glass manufacturing plant — a light bulb manufacturing plant, part of their lighting division — they used to make light bulbs, I'm sure under license from Corning technology. Bob would stop by before he would lecture 3.091 and pick up some freshly made light bulbs, bring them into class, and an hour later he would throw them against the wall, and they'd just bounce off the wall. Try that the next day, and they shatter. He didn't do it the next day, but freshly made glass is extremely strong, because it has no surface flaws — it hasn't been corroded by the moisture in the air yet. Does that answer your question?

Thesis advisor Bob Rose stopped at the Sylvania Beverly plant before 3.091 lectures to collect freshly made light bulbs, which he then threw across 10-250 — they bounced because moisture had not yet attacked the surface.

The story I know is, my old thesis advisor Bob Rose lives up on the North Shore. Sylvania had a glass light bulb manufacturing plant up there in Beverly. He used to lecture 3.091 back in the days when I was a student, and he would stop and get freshly made light bulbs on the way in before his lecture. He would take the light bulbs in 10-250 and throw them across the room, and they'd bounce. They wouldn't shatter, because they were freshly made. They did not have surface imperfections that caused them to fracture.

Rose's 3.091 demonstration — fresh light bulb from Sylvania Danvers plant bounces off wall; day-old light bulb fractures. The point: sodium/potassium oxide corrosion by atmospheric humidity within hours creates fracture-mechanics-relevant surface flaws.