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 
