VOLUME VARIATION OF BOTTLED FOODS. 3 



collected. The lump of glass attached to the punty is rolled into 

 a pear-shaped lump on an iron plate, placed in a mould, and the glass 

 expanded to the limiting mould walls by blowing through the punty. 

 As soon as the mass has been expanded to the limits of the mould, the 

 punty is detached, the mould opened, and the bottle removed. The 

 neck is then reheated and finished and the bottle placed in a cooling 

 chamber, where the temperature is gradually reduced. 



The semiautomatic machine process embodies the first attempts to 

 apply machinery to the blowing of bottles. A stream of glass falling 

 into the mould is cut off by scissors operated by a foot treadle. Since 

 practically all of the glass which falls into the mould is contained in 

 the finished bottle, its weight depends upon the judgment of the 

 operator of the foot treadle. The molten glass is formed roughly 

 in a blank mould by a plunger, and it is then transferred by hand 

 to the blow mould, where it is blown by compressed air to the limits 

 of the walls of the mould. 



The automatic machine process accomplishes all steps of bottle 

 manufacture by machinery. The amount of glass is gauged by 

 filling a hollow mould by suction and striking off the excess glass 

 with a knife. The weight of the glass in the bottle is that measured 

 into the mould. After forming the neck of the bottle in this mould 

 the blow mould is brought into position around the pencil of glass, 

 which is expanded to the mould limits by compressed air. 



In both hand and semiautomatic machine processes the weights 

 of the bottles are controlled by the accuracies of human judgment, 

 in the first case in properly estimating the weight of molten glass 

 on the punty, and in the second case in -properly estimating the 

 amount of glass which drops into the mould. In the automatic 

 machine process the weight of the bottle depends upon the amount 

 of glass measured into the mould by machinery and does not depend 

 upon the accuracy of human judgment. So far as the manufactur- 

 ing affects the weight of the bottles there are only two processes, 

 hand and machine, the semiautomatic machine process falling into 

 the first class. 



In all processes the mould is manufactured according to strict 

 specifications and tests. Its cavity, which controls the exterior di- 

 mensions of the bottle, is accurately machined to previously deter- 

 mined dimensions, and sample bottles are blown for weight and 

 capacity tests before it is installed. With continual use a scum ac- 

 cumulates in the mould, slightly diminishing its interior dimensions. 

 After this scum has been removed a sufficient number of times, the 

 mould's dimensions become appreciably larger, so that a new mould 

 must be substituted for it. Much attention is given to the cleaning 

 of the mould and to the possibility of its replacement by the bottle 



