In reply to oldie:
> Vague memories of preventing violent boiling in school lab by adding inert particles or lumps eg marbles (?). Presumably something softish and nontoxic would be less noisy.
Do not ever try to boil marbles!
I did. I nearly died.
I had a good reason for doing so as I needed some completely sterile weights as part of making beer. I thought boiling them would be a great way of sterilising them. What actually happened is one of them exploded and it set off a chain reaction of explosions. A bit like making popcorn but with glass shrapnel effects for added fun. A actually pulled some glass fragments from the plaster on the ceiling.
Don't ever boil marbles.