[Stoves] A heat-resistant insulation mix

[Xavier Brandao]

Hey everyone,

Roger said: "is your space between the walls sealed enough that you might be
able to use plain old sand? Is sand available to you plentifully enough?"
I'm afraid it is not fully sealed, we try to have a plain and nice-looking
welding, but there are often a few holes left. It is not totally hermetic.
Sand is available, even if the government has forbidden sandpits on the
coast, it was causing coastal erosion.
Is sand that good an insulation? I always heard it was too dense ... I think
it would make the stove heavy also. What about its expansion when submitted
to a high heat? Crispin says in his paper Development of a low thermal
expansion ceramic body: “One of the most important changes that occurs in
any clay happens at 573° when free Silica (ordinary Quartz sand) changes
from an Alpha to a Beta crystal structure and increases in volume by about
1% over a very small temperature range.)”
I don’t know how hot a big institutional stove in operation is.

To Crispin: the 3D printing technology is amazing. One day, we’ll all sit
and sip cold drinks while watching these machines work for us.

To Larry: very interesting! “Self-firing”, “vitrify”, you are putting words
on a process I was only guessing. I can assure you that when we first put
the clay-sawdust mix in the institutional stove, we didn’t know what we were
doing! On a website for potters, several types of clay are for sale:
“True ceramics are fired at over 2000 degrees F, which turns the clay into a
glass-like material.”
“This is a self hardening clay - no need to cure in an oven or kiln.”
“this clay will harden after baking for one hour in your kitchen oven at 350
degrees F”
There’s a website explaining how to fire the clay-horse manure mix:
http://www.claytonbailey.com/internalcombus.htm 
It is self-firing, but seems better in a “well insulated and tightly packed
kiln chamber” at 500 degrees farenheit (260 degree celcius if I am correct).
Why horse? Not so many horses in Africa 

Camel or donkeys aren’t so many either, perhaps we’ll try with cow or sheep
dung. I didn’t find info about the mix on bioenergylist, I contacted Jon
Anderson by email.

Many thanks,

Xavier