680 GEOLOGY OF OHIO. 
making about a ton to an ordinary press. To fill a press requires 
about 45 minutes. The clay upon coming from the press is in a soft 
and plastic state, and is kept in a tight room or under blankets till used. 
The ware is burned in “saggers,” or small clay receptacles, which are 
conveniently shaped to hold the ware, and thus protect it from the 
direct action of the fire; these saggers are in use in all potteries except 
those making stone-ware. They are made of the native clays for yellow- 
ware, but for white-ware they use a clay imported from New Jersey. 
The qualifications of a clay to make good saggers, are plasticity and 
refractoriness and an absence of a tendency to crack. If all of these, 
its success is assured; that is the reason why Ohio clays are not 
wholly used, because our Coal Measure clays, when plastic, are impure 
as a rule, and hard clays, though refractory, are not plastic. The saggers 
made from Ohio clays are in constant use at the yellow-ware works, 
however, and answer all purposes well. The old saggers, ground up 
fine, serve as non-shrinking material, and just as little green clay is used 
each time as will make the bond thorough and complete. The average 
life of a sagger is about 15 burnings. The stock of saggers necessary 
~ to be kept on hand is quite large, and it keeps several men busy in 
most works preparing them. ‘The ware is put into them, but is sup- 
ported on little triangular pins stuck in the side of the saggers so that 
it touches nothing but the knife edges it rests on. The manufacture of 
these pins and other devices of the same kind affords business to two 
firms in East Liverpool. The sagger is piled full of ware, all arranged 
so that the pieces do not touch the wall cr each other; the top of the 
sagger is then luted with soft clay, and each successive sagger forms the 
roof of the one below, the clay making an air-tight joint. The kiln 
cha.zber is piled full of saggers, and luted shut, and the fire set. This 
is started slowly and raised steadily for 48 hours and cooled as long. 
When opened the saggers are removed, unpacked, and set aside to be 
inspected before they are used again. ‘The clay itself, the qualities it 
needs to be valuable, have been noticed already. The excellent clay, used 
at Liverpool, shows on analysis : 
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