232 GEOLOGY OF OHIO 



outside portion. Strange things are often found imbedded in the bottom 

 of old glass pots; bolts, nails, lumps of metallic lead, and all kinds of 

 iron objects, added with the charge through carelessness or spite. 



These old shells come from pots previously made and numbered 

 and of whose number a record is kept, and can be thiis identified as to 

 composition and graded accordingly so that no uncertainty of composi- 

 tion is encountered by their use. 



The charge when mixed is ground in a dry pan, and tempered in a 

 pug mill, by repeated passages through, When tempered, the clay is 

 piled in large masses and compacted by hammering till solid, and 

 blanketed to undergo a process of sweating or steeping. 



By common opinion among glass pot men, this steeping is a very 

 important part of the work. It is hard to see from a theoretical stand- 

 point where the value of this process comes in. The only reason that 

 can be suggested, is that the grinding of the clays, especially hard clays, 

 exposes more surfaces to the action of the water than would be exposed 

 by a natural process of cleavage by weather and that a long process of 

 soaking may induce a softening of its nature not otherwise attainable. 

 It is claimed that the quality developed by long standing is toughness; 

 that clay newly mixed is short grained, while old clay is cohesive, like 

 rubber. 



Whatever may be the truth of this claim, the universal practice is 

 to allow as long a period to elapse as possible between the mixing of the 

 clay and the using of it. In some cases as long a period as two years is 

 allowed to pass before the clay is used. 



The various parts of the glass pot are constructed of different mix- 

 tures of clay. The top of the pot has only to stand the heat and bear 

 up its own weight. The bottom has to stand the weight and the scorify- 

 ing action of the glass. The sides have the severest work of all, having 

 to maintain the weight of the roof and the inside pressure of the molten 

 charge. The usual point of failure is eighteen to twenty four inches 

 above the bottom of the pot. 



The actual process of manufacture is one of slow building. A pot 

 is built up in sections of a few inches ever}- day. Each days work is 

 welded onto the last, and the new work is kept from becoming too dry 

 by wet cloths. Thus the process continues until completion, which 

 occupies from one month to six weeks. A pot maker will have twenty 

 or thirty pots in treatment at once, in various stages of progression. 

 As fast as one crop comes off, a new one is blocked out. The drying it 

 most carefully managed in perfectly tight rooms; no heat is used except 

 to prevent freezing and no draughts of air, above all things. A month 

 or six weeks of air drying is allowed, followed by a few days of heating 

 in a hot room, preliminar}'- to shipment. 



The pots are never burned, except in the place where they are to do 

 their work. They are put in position and heated very gradual!}' up to 



