Up: Glassmaking
Flat Glass: 31 of 66
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removed and dipped for a few seconds in a hot bath of
diluted hydrochloric acid. This dipping process arrests
any further action of the alkali that is used in the
original glass batch and prevents the glass fading through
the action of the elements.
A little reflection upon the physical
characteristics of the split cylinder in passing from its
cylindrical form to the flat sheet is interesting. It can
readily be seen that in the flattening process previously
described, the attempt is made to force the inside
circumference to equal that of the outside. This is
manifestly impossible since the glass cylinder is heated
only to the bending point.
The result of this fact alone is
that this ironing out or flattening process cannot produce
an absolutely flat sheet of glass and the finished sheet
will have an appearance similar to hammered brass or else
it will be full of long, irregular waves. Both conditions
produce unpleasant effects of distortion
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