Time-frame is the late 1960s: I have recollections of waiting in the wings to go on stage for ballet performances. The head ballet teacher would always remind us to be so careful of the steam trays. There were two of these trays; from memory, kitty-litter-tray size and shape, but metal. Hot steam issued from both trays, which were at the front of the stage, just at the side of each wing.
They were only in place for actual performances, not rehearsals, dress rehearsals or practice.
I can recall the principal dancers complaining about them and having to avoid them.
What were these trays and what was their purpose?
I have been attempting to research this for some days with no luck: I obviously need access to dancers of the 1960s or history books of that era. Can anyone either answer my queries or direct me to someone who can, please.
All people who help me in any way with research are always credited at the end of the book/story for their kind assistance.