The grinding, by means of these rollers, may add 50 cents
per thousand to the cost of the tiles, but it will greatly improve their
quality.
In the spring, the clay should be prepared for tempering, by the removal
of such pebbles as it may still contain. The best way to do this is by
"washing," though, if there be only a few coarse pebbles, they may be
removed by building the clay into a solid cone 2 or 3 feet high, and then
paring it off into thin slices with a long knife having a handle at each
end. This paring will discover any pebbles larger than a pea that may have
remained in the clay.
_Washing_ is the process of mixing the clay with a considerable quantity
of water, so as to form a thin paste, in which all stones and gravel will
sink to the bottom; the liquid portion is then drawn off into shallow pits
or vats, and allowed to settle, the clear water being finally removed by
pumping or by evaporation, according to the need for haste. For washing
small quantities of clay, a common mortar bed, such as is used by masons,
will answer, if it be supplied with a gate for draining off the muddy
water after the gravel has settled; but, if the work is at all extensive,
a washing mill will be required. It may be made in the form of a circular
trough, with scrapers for mixing the clay and water attached to a circular
horse-sweep.
"Another convenient mixing machine may be constructed in the following
manner: Take a large hollow log, of suitable length, say five or six feet;
hew out the inequalities with an adz, and close up the ends with pieces of
strong plank, into which bearing have been cut to support a revolving
shaft.
Pages:
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211