I got to thinking about vacuum tube and I was wondering, if you suck all the air out of a tube to make a vacuum tube wouldn't than mean that the pressure differential would crush the glass/tube?
The fact that millions of vacuum tubes and incandescent light bulbs have been sucessfully manufactured is proof that glass can survive the pressure difference.
I guess it depends how thick the glass is. But yeah, 30psi you'd think would be enough huh? After seeing how it can crush other things in vacuum bagging operations. It could be that the glass is deceptively fragile because it is brittle, not because it's weak, after all we have things like fiberglass reinforcement.