All depends what you have avalible in your part of the world. Propane, coal, coke, charcoal, wood, corn cobs, all is suitable some burn faster than others but will all work to make blades, but if ya can't get coal (preferably bituminous , anthricite is a pain IMO) don't build a coal forge . Same for any of em... Grab a cold drink and start reading in the forges section and see what may work with what you have avalible you have a lot of options.