Chemistry in the Industries 297
made with acrylate resin, bulges under impact and thus
absorbs the kinetic energy of the blow. To develop bird-proof
windshields for airplanes, Westinghouse shoots previously
electrocuted poultry from a 20-foot air gun at a pane of
glass. One type of panel developed has tempered glass on
the outside, an air space, then two panes of glass holding a
half-inch filling of plastic. These panels protect from a 300-
mile-per-hour poultry bullet.
One of the first industries in America was the manufacture
of glass. In 1608, Captain John Smith established a glass fac-
tory at Jamestown, Virginia. During the following three
centuries the glass industry was essentially a rule-of-thumb
process. Today the glass industry has emerged from the ages
of closely-guarded secret formulae and empirical processes, to
a full use of the tools of modern science. The outstanding
advantages of glass are its inertness, durability, transparency,
and cleanliness. The Corning Glass Works has developed a
glass with high heat resistance coupled with high chemical
stability. This “Pyrex” glass has the lowest coefficient of
expansion of any commercial glass, which makes it un-
equalled in its ability to withstand sudden temperature
changes.
The first glass-lined steel tanks were manufactured solely
for the bulk storage of malt beverages. Their advantages
gradually led to their adoption by other industries, par-
ticularly chemical and food. The linings are of complex boro-
silicates which are fused to the steel at temperatures averag-
ing about 18000 Fahrenheit. It is the glass-lined tank car
and truck tank which has made the hauling of bulk milk
practical. The thermal expansion of these enamels can be
conveniently controlled by adjusting the sodium oxide and
the boric acid contents, the former raising the expansion and
the latter lowering it.