CLAY MANUFACTURES. 695 
asarule. The molds used on the presses are changed with ease, and a 
set is usually kept, including all kinds of arch and key-brick, together 
with special shapes. Any special design can be speedily made to order 
also. ‘These machines are also made in larger sizes to press such wares 
as furnace blocks, but they are not incommon use. The sixth step in 
the fire-brick process is the most interesting of all; it is the burning of 
the ware, now dried and pressed. This part of the work calls for more 
technical skill than any other portion. The considerations to be noticed 
in this connection are, first, the kiln; second, the manner of drawing 
and setting; and lastly, the points observed in the chemistry of the 
process. 
The different kinds of kilns used in fire-brick manufacture can only 
be touched upon here. They may be classified as: 
( Without rool—Minedaatisid Crea-sccnsetscecsse-cessesescsses 1 
| Up draught — Meee Pine dua tigi elccwdn. wsesets inecon oe cenc ees 2 
eee UREN Oot a neeeten eet Su erate 3 
tee Poel Cine ularye ee ede ee ra eee ee A ; 
| Down dennght—| pine GUAtUSTG Cleiectncscns. acess deacsneueceres 
L Reclaueulacinimired atiendi ttn cs) ee. 6 
All of these are found in Ohio, with several other forms differing 
from these types by small features, but the three kilns in wide use are 
Nos. 1, 4, and 6. 
The first and simplest kiln employed in fire-brick manufacture is the 
rectangular, up-draft kiln without any roof. Its use is still very large . 
and it suffices to burn much of the best brick in the State. It consists 
of four walls of common fire-brick, from 18 to 24 inches thick, lined 
with the best grades, and built on firm stone foundations. ‘The side 
walls are perforated by the openings of the fireplaces from outside, and 
the ends are provided with doors through which the kiln is set 
and drawn. The fireplaces are built either separate or in one con- 
tinuous block. They are small covered chambers, running direct back 
into the kiln; the grates are set in a standing position so that the whole 
aperture can be filled with fire during the culmination of a hard burning. 
The dimensions of this style of kiln vary from 10 to 14 feet wide, 11 to 
12 feet high, 25 to 40 feet long, and from 50,000 to 75,000 bricks capa- 
city. The burning varies with the hardness desired, character of brick 
and fuel, etc., from five to eight days; perhaps six days is the most usual 
time. The brick cool from two to four days, according to the need in 
which they are held. These kilns are used in the whole Sciotoville 
