[TheForge] Re: Kaowool

[Mike Porter]

I have built about twenty small forges and casting furnaces and overseen
construction of at least that many more for students, employing both Kaowool
and castable refractory as their main linings. While preferring toughened
ceramic fiber for forges (a 1/4" to 1/2" penetration of rigidizer coated
over with sealant/IR reflector), this is mainly to keep weight minimized. A
five gallon or smaller forge lined with Kastolight 3000 should take ten
minutes for its lining to become lemon yellow. The same equipment lined with
treated & coated ceramic fiber should take two (you don't want more heat
than lemon yellow on refractory fiber). Cool down time for the fiber lined
vessel is about twenty minutes; perhaps two hours for the other. These
differences can be positive or negative, depending on your needs. When ready
to leave a demonstration site, two hours is an unacceptable inconvenience,
to say nothing of the additional fifty pounds being carried. On the other
hand, continued warmth on your backside--without worrying about caching your
britches on fire--is mighty nice on a cold winter's day. There can be no
arguing with the advantages or a tough castable for working billets.
Sustained high temperatures used for billet heating will shrink ceramic
fiber in hours--not days or weeks.

Your personal refractory choice should always be tied to your main goals; it
should be an informed choice springing from an understanding that no ceramic
material is perfect--we don't live in a perfect world. Fiber or castable,
brick or kiln shelf, perlite, vermiculite, calcium board, or even mineral
wool, should all be selected primarily with your goals in mind. Secondary
considerations are availability and finances, but mistaken loyalty to some
material or design is ridiculous; we're not talking about shooting Old
Yeller--it's just another machine; be ruthlessly dispassionate.
Mikey