Cast iron windows need stripping 80+ years of paint, whats the best to use?

Heat gun

Portable shot blast

heat and glass not a good mix
shot blasting again damage and mess are high
maybe have a look at Peelaway or the like, put as much on as you can and cover then leave for 24-48 hours then peel off.
Worth a go with small area ??

Rob, try an old but still sharp’ish chisel and use it to scrape (but using a pushing action) the paint off. If the paints old and thick it should just flake/chip off. Bit of a rub down with wire wool and a coat of primer and they were sorted.
I had to do loads at a place in Mcr and was given all sorts of chemicals to use, I decided that they’d make way to much mess and trying to clean up a gooey paint/chemical mess off anywhere was not on my list of priorities.