[Sca-cooks] clay for ovens

[Phlip]

Ene bichizh ogsen baina shuu...

> I think I remember that the usual additive for clay is straw to combat the
> cracking problem.  Something in the back of my mind says horse manure may
> figure into this as well.
>
> Simon Sinneghe

Understand, that this is NOT an area of my expertise, at all, however...

I suspect most of us may remember the Biblical stories of the Jews in Egypt,
leading up to the move into Israel, led by a fellow named Moses ;-)

If you'll recall, one of the "evil" things that the Egyptians did to the
Jews was require that they make their bricks _without_ straw.

Also, in the Pirotechnica ( 1540- a treatise on metallurgy in the MA-
Italian) they instructions for constructing a forge include mixing the clay
for the lining with horse manure. It's essentially a rammed earth lining for
a wooden forge (Gee- anybody wanna guess about what one of my projects in
the near future is? ;-)

My thought on this is that the fibrous organic content helps provide a
stabilizing structuaral element for the plain clay, similar to the rebar
used in concrete structures. Most of the items _I_ have seen that use a
"fabric" of some sort for reinforcing a hardened amalgam such as clay or
concrete tend to be  rather thick items that would tend to receive a lot of
stress, as in foundations or walls for buildings, or roads, whereas
something like a sidewalk wouldn't, when you're discussing concrete-
similarly, if you're using clay as a structural element, as in a forge or a
brick for a wall, the clay or horse manure would stabilize the structure,
and that at the surface would burn out, leaving some imperfections of the
surface, which you would neither want nor need with something as thin walled
as a plate or a bowl.

Horse manure, btw, for you city folks, does tend to retain quite a bit of
fiber in it, because a horse's digestive system is less efficient than
cattle's multi stomach system. It's one reason that oxen are highly
efficient farm animals in applications which don't require speed- they
require less food per amount of work done, because they use what they get
more efficiently.

Hope this helps a bit...

Saint Phlip,
CoD

"When in doubt, heat it up and hit it with a hammer."
 Blacksmith's credo.

 If it walks like a duck, and quacks like a duck, it is probably not a
cat.

Never a horse that cain't be rode,
And never a rider who cain't be throwed....