It's a torch ,and I've seen better.........it's probably done with heavy oil and propane......I do know that if the metal is polished up to a mirror finish ,then dipped in the oil ,and heated from sharp corner's out, the torch will color it in second's with no great amount of heat.........

I AM NOT ENCOURAGEING THIS ,JUST STATEING OBSERVATION'S I HAVE MADE (with all kind's of metal)
Actually,I regret this post already