Found Dreaming

OK, just a writeup of my first real furnace (Im not counting my crazy, all portland mortar, charcoal fired debacle):

The shell is a water expansion tank from a hot water heater. I want to say it was about 13" or so across - found it on the side of the road = Free!


Cut open and legs attached with sheet metal screws. Legs were leftover from a garage door kit = free:


A styrofoam plug for the drain:


Foamed castable in the floor:


half inch hotface on the floor:


1 inch strips of ceramic fiber board insulation:


inner form installed, and 2" PVC tuyere form installed:


1" hotface cast:


And the final result is an 11 inch bore, and a 16" depth



I currntly use a section of ceramic board coated in refractory to hold the fibers together for a lid. I need to get cracking on a real lid with a lifting mechanism...lifting the lid with gloved hands is often...uncomfortable. The refractory is chicago firebrick dense alumina castable - got the torn bag free from the remnants bin at a boiler installation place. Same with the ceramic board - corner was broken off and they just wanted to get rid of it.

So this furnace with real castable refractory and ceramic insulation was totally free. A little scrounging can go a long way

How is the insulation on the fiber board? Have you measure the temperature of the outside after it has been running for awhile?

ive been up to a decent yellow heat before - i took a stab at aluminum bronze once and i came close. the exterior was hot enough that carrying the furnace very far was uncomfortable with welding gloves on. but overall is pretty good. i shouldve taken my time and made a better inner core mold for a thinner hotface, the inch thickness takes a loooong time to heat at first, but then climbs pretty quick, and holds temp for quite a while.

I like the idea of a 1" hotface and plan on my next furnace rebuild to have a heavy hotface. That thing will last a long time with no worries.