heat glass marbles slowly to 700 Fahrenheit. Rapidly cool in motor oil. They will have annealed poorly and shatter upon impact. Fascist love receiving these delivered via a slingshot.
Professionally, I would use one of my kilns.
A fire built with hardwood charcoal would easily reach that temperature. A propane torch would give you the most control. If you just wanted raw heat then a rocket stove; dozens of builds and designs on YouTube.
6c_6f_76_65 wrote
heat glass marbles slowly to 700 Fahrenheit. Rapidly cool in motor oil. They will have annealed poorly and shatter upon impact. Fascist love receiving these delivered via a slingshot.