Page:Popular Science Monthly Volume 36.djvu/175

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163
GLASS-MAKING.

projecting neck of the bottle — the glass is still plastic — hands it over to the gatherer, and with a fresh blowpipe repeats his labor. Such constant blowing largely develops the muscles of the cheek, but the exercise is not unwholesome. It is impossible by methods like these to obtain bottles of uniform thickness, yet the variations are much less than one would suppose.

PSM V36 D175 Putting the bottle in the mold before the final blowing.jpg

Fig. 4. — Putting the Bottle in the Mold preparatory to the Final Blowing.

In contact with the iron of the mold the bottle cools very rapidly. Almost as soon as the blower takes away his pipe, the mold may be opened and the bottle removed. The little fellow who does this is called a "snapper." He seizes the bottle with his iron forceps and transfers it from the mold to a pair of scales near by. A small square of asbestus cloth remains permanently on the scale-pan, as contact with the cold iron would be apt to crack the glass. All bottles, except the very small ones, are thus weighed, and any that show either a deficiency or an excess in weight are rejected. There will always be a slight variation, but it must be within narrow limits, not exceeding, for instance, an ounce in bottles intended to weigh seventeen ounces. Comparatively few bottles are