On Fri, 25 Oct 2013 16:56:40 -0700, Paul Drahn

wrote:
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One big question is what they used
to bind the sand and clay to make molds. Could they have used lard oil,
or other animal products?
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http://en.wikipedia.org/wiki/Sand_casting
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Sand casting is relatively cheap and sufficiently refractory
even for steel foundry use. In addition to the sand, a
suitable bonding agent (usually clay) is mixed or occurs
with the sand. The mixture is moistened, typically with
water, but sometimes with other substances, to develop
strength and plasticity of the clay and to make the
aggregate suitable for molding.
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see section on green sand

http://en.wikipedia.org/wiki/Molding_sand

http://www.youtube.com/watch?v=U7ut_2nqiGk

http://www.youtube.com/watch?v=HHk-zvJ_jr4