First try at melting metal

[Sunset Machine]

Yes indeedy, air is for cooling. Amongst other things, I used to service and repair landfill gas extraction flares. The EPA set regs as to temps, they were monitored with overpriced Honeywell digital temp controllers which controlled simple motorized shutters on the secondary atmospheric air intakes on the sides of the flare stacks. The gas was from constant speed blowers through manually adjusted butterfly valves. That adjustment determined the quality of the gas coming from the field, if too rich then open the valves a little and build a bigger fire. It needed to hold a negative in the field to prevent methane from getting into houses and was influenced by who-knows-what-all. All very basic stuff, just large. I could light the sky or rattle windows for miles around with those things. Lots of control.

'Twere me, speaking as a 30 year industrial burner mechanic in a variety of installations, an air shutter would be preferred over blower speed control. I can honestly say that I've never seen speed control used for that. Look at blower performance curves and you'll see why. Not that it won't work, it just works better if you throttle the air. More precise control.

Speaking of rattling... I've wandered. Melting cast iron! I bought Colin (The Artful Bodger) Peck's book on backyard foundries using waste oil - very interesting. British, I think. He's melting cast iron with old motor oil. ISBN 0-9546895-1-8