"
"That is pretty clever," replied Theo.
"Yes, it is a very ingenious device," Mr. Marwood agreed. "The
blungers in which the clay is mixed are over there. You can see
them--those great machines near the centre of the floor. They are
heavy steel tanks lined with vitrified brick, and in the middle of
each one is a revolving contrivance, with steel arms and teeth that
grind the clay up very fine and blend it thoroughly. While it is being
mixed in this way water is added to it, and also a certain amount of
powdered oxide of cobalt to whiten it."
"Just as we put blueing in clothes," Theo ventured.
Mr. Marwood assented.
"This cobalt has already been pulverized and sifted most carefully, so
there will be no particles in it, and so it will readily
dissolve. After the clay mixture has had this mauling--for I can call
it nothing else--the blunged compound, or slip, flows in liquid form
into the sifter machines where it is strained through silk gauze or
else a mesh of fine copper wire."
"I shouldn't think you could ever strain such stuff," Theo declared.
"The sifters do get very hard wear," answered Mr. Marwood, "and are
the machines most liable to get out of order.
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