Original" just means it's been falling apart for a century, not that it's good.

Man, that's a slick move with the sponge. I read a forum post once where a guy swore by keeping a spray bottle with just plain water and a tiny bit of liquid soap mixed in. He'd give the surface a super light mist right before the final trowel pass. Said the soap helped it spread without marking up the cream. Another old timer told me he'd have his helper lightly sprinkle a fine mist from a garden hose over the slab while he worked behind them, but you gotta be SO careful not to overdo it and wash out the surface.

Yeah, the quiet ones are watching everything. Best thing you can do is give them real problems to solve, not just busywork. They'll surprise you when they actually care about the task.

Good point about the warping. Seen that happen a few times myself. Firebrick is definitely the way to go for a long term fix.

Wasn't it just begging until my cat did it during a storm?