Potassium piece, size limit?

If they want bigger tell them to measure up the bowl and you the details so you can use cleapss calculations to work out the maximum size you can use....what ever the size they give you always tell them 3 mm :D

I think mine go out a bit larger than that. Last year we had a couple of clashes where 2 teachers wanted them at the same time so my HoD got the brand new bottle of potassium as I know she would use a small amount where I would happily take the kids outside and chuck the lot in :D
3-4mm is sufficient. I have it ready cubed in small jars. A teacher once put in a big chunk, broke the trough, scared the living daylights out of the students and herself and caused a near breakdown for the H&S gnome. Don't take any chances now and it's us who clean up their messes.
I had a teacher carefully cut of the required size, put that back in the beaker and put the large piece in the trough....
Did it take out the trough or was everything ok from it?
Trough was OK, but the potassium hit the ceiling and went all over the desk. Took an hour clearing up. Of course all the pupils were shouting " Do it again Miss!"