[TheForge] A challenge to Harry

[Kathy]

Harry,
ITC #100 is an infrared reflector (actually a re-radiator) the only protection
it provides ceramic blanket is in cutting down the amount of conducted heat
energy into the blanket's interior from its hot-face side; this protection is
real, but is limited. Over time, the blanket will still overheat and shrink; to
understand this, look up both the dropping insulation values over an extended
heating cycle, and the percentage of shrinkage expected as the heating cycles
are repeated.  The first thing this shrinkage leads to is spalling of areas on
the hot-face surface, because the ITC #100 coated area is unable to shrink along
with the rest of the ceramic blanket; instead, it temporarily expands somewhat
from the great heat it is generating. If you are looking for a protective
coating, rather than an IR reflector, you would probably be much better served
by Plistex from Larry Zoeller. He showed me an treated sample at the ABANA
conference in Kentucky. It was pretty impressive.

Bubble alumina is expensive; far more expensive than Kastolite 3000. Nor do I
believe it is more insulative than the Kastolite refractory. It is, however good
for another 1000 degrees temperature increase over K 3000. How frequently you
have to do repairs on any ceramic blanket depends on how high a temperature is
reached in the forge/furnace; If you turn one of my tube burners up sufficiently
to create a white hot interior, you can count on doing repairs to the facing as
soon as the equipment cools down >:-)

Is it necessary to do so, even for casting? NO, but it is quite a temptation for
some of us (voice of experience here). 
Mikey



-----Original Message-----
Mikey,

    How do they compare dollar for dollar? I presume kastolite 3000 is a
castable refractory, but I haven't heard of bubble alumina. I thought the whole
idea of the ITC  100 was to protect the ceramic blanket for more durability. And
by frequent, how frequent?

Harry

Kathy wrote:
> Harry,
> If you plan on making a good forge/furnace it would be a much better 
> idea to use Kastolite 3000 refractory or bubble alumina instead of 
> ceramic blanket. I do strongly urge you to reconsider your insulating 
> refractory choice, unless you don't mind replacing the ceramic blanket on a
frequent basis.
> Mikey