From the mixer the melada is drawn into the centrifugal machines. These
consist, first, of an iron case resembling in form the husk of mill
stones. A spout at the bottom of the husk connects with a molasses tank.
Within this husk is placed a metallic vessel with perforated sides. This
vessel is either mounted or hung on a vertical axis, and is lined with
wire cloth. Having taken a proper portion of the melada into the
centrifugal, the operator starts it to revolving, and by means of a
friction clutch makes such connection with the engine as gives it about
1,500 revolutions per minute. The centrifugal force developed drives the
liquid molasses through the meshes of the wire cloth, and out against
the husk, from which it flows off into a tank. The sugar, being solid,
is retained by the wire cloth. If there is in the melada the "false
grain" already mentioned, it passes into the meshes of the wire cloth,
and prevents the passage of the molasses. After the molasses has been
nearly all thrown out, a small quantity of water is sprayed over the
sugar while the centrifugal is in motion. This is forced through the
sugar, and carries with it much of the molasses which would otherwise
adhere to the sugar, and discolor it. If the sugar is to be refined,
this washing with water is omitted. When the sugar has been sufficiently
dried, the machine is stopped, the sugar taken out, and put into barrels
for market.
Simple as the operation of the centrifugals is, the direction of the
sugar boiler as to the special treatment of each strike is necessary,
since he, better than any one else, knows what difficulties are to be
expected on account of the condition in which the melada left the strike
pan.