Soft firebricks: long-winded answers
David Barnett - Venice, FL
>"Is your brick drilled all the way thru end to end?"
Yes. I have two 3/4" holes at the end; one near the top, one near the bottom. The front is the same as the pic. The torch port is slightly slanted to the rear. The bricks are soft enough to cut and shape with rasps and smooth with coarse sandpaper, btw. I have nice rounded edges which seem to help keep it from crumbling. I also have a small hole for the probe on my digital pyrometer.
"How long does a brick last?"
I don't know yet. I dropped my first one as the thick Kevlar furnace gloves added to my own clumsiness. (Too impatient to let the thing cool after a long session. Short sessions just get it warm.) My second brick has lasted about three years with fairly frequent use, and that's with oxy/propane as well as propane/air. The bricks in my electric kiln are the same type and have been through hell: enameling, casting glass (pate de verre), kiln soldering, mokume gane, etc., and are still completely fine (one normal hairline crack in one kiln brick that won't require repair or replacing for years). I use these bricks to improvise all manner of muffle furnaces, kilns, melting clusters, offhand forges, and they seem to just go on and on. I don't even think about wearing them out, unlike casting refractories that get baked to death from glass casting kiln schedules that can last a day or longer. My two-brick mokume gane kiln/furnace (after Steve Midgett's design) has had only intermittant use so I can't say much about its longevity. I also have a half brick that supports an inset 'trinket kiln' ceramic electric element topped by a 1/4" thick unglazed tile. I run this all out while fusing silver or gold jump rings (no solder) with an oxy/propane torch (the kiln keeps them closer to fusing temp). I have done this for 8 hours a day for weeks and that brick is fine.
"What type of raw materials to you use?"
The raw materials I work in a one-brick micro-forge (and furnaces of soft firebrick) are W1 cold drawn square drill rod, O1 flat and drill, cut and round concrete nails, mild steels (occasionally).
In the two-brick mokume gane kiln I've eutectically bound silver, copper, gold, shakudo, nickel, etc.
In stacked brick furnaces, I've melted fine silver (.999) and sterling (.925) in open crucibles.
In soft brick electric kilns I work pure copper, pure silver, high karat golds, Gaffer 45-percent lead crystal frit as well as Bullseye and Uroboros frit.
I melt 24K gold for alloying with pure silver and copper to make 'alluvial' 22K for fusing and granulation in compressed charcoal blocks only.
