I should have timed how long it takes to get to melting temperature (I will next time), but a rough estimate was it took about 15 minutes with the old Harbor Freight torch, and less than 5 minutes with the new burner.
Insulating firebricks should get up to temp faster, as they're less dense and with better insulation properties.
They mightn't last as long, tho. Kinda brittle, and to be able to stand up to the flame for melting brass:
The "26" variety of up to 1400°C / 2552°F is also pretty expensive.
You could also DIY an insulating refractory out of silica sand, bentonite clay and perlite (found at garden supply stores) as aggregate,
and use ordinary cheap waterglass as a binder.
The suggested proportions of aggregate and binder are as many as there are Backyard foundry sites, tho.
Seems like they'll eventually crack, some more than others, (the foundries - not the sites!) and YMMV.
Mine did, after about 15 charcoal briquette burns. 2" wall thickness and still you didn't burn yourself on its sides.
Personally: I'm aiming for a max 1350°C, 4 kW 10A 400VAC electric foundry with J26 insu-bricks:
easier to cut, no binder, also silent in operation, less hot fumes, no flame,
but much slower than a fiery, roaring, honcho burner.
Probably a thread here one of these days...
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