Wiktionary
steam up
vb. 1 To become steamy. 2 To become coated with condensation. To fog up.
Usage examples of "steam up".
Do we steam up to the collier or the blacksmith wearing black and say, 'Oh, I'd like to buy ten stone worth of coal or charcoal'?
What's the record for activating the plant, getting steam up and spinning the turbo generators?
Jason's assistants had the boiler hot and a head of steam up: the tests began.
It also had steam up, so its tall, thin single stack exuded an ooze of dirty smoke and a steady drift of soot that did not go very high in the air before descending, on deck and dock impartially, like a sticky black snow.
She also had full steam up and her deck-cranes rigged to unload cargo.