On Nov 02, 2010, at 05:22, nigel mccarty-eigenmann wrote:
What mineral contents would make a brick come out of the oven blue,
green
and black?
Usually, bricks are only colored on the surface by applying a glaze
(called "slip") to the green brick before firing. Coloring the brick
paste itself is generally cost-prohibitive, but it can be done.
Blue - usually cobalt oxide
Green - probably some combination of chrome, cobalt, or uranium
oxides, depending on shade and firing method
Black - perhaps iron oxide in a reducing fire, but it might tend to
change color as it ages
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