ELECTRO-GLAZING LUXFER PRISMS.
Electro-glazing is a process by which
small pieces of glass, such as prism lenses, may be united together
to form a broad thin plate. These plates, composed of Luxfer Prisms,
when used in windows, must be strong enough to resist high wind
pressures. The old cathedral glass, composed, as it is, of small
pieces leaded together, or united by zinc or other such framing, is
found to be very weak. Such windows have to be supported by rods
and bars, and even then windows are constantly giving away under
the pressures of high winds. It is found by actual test that pieces
of glass thus electro-glazed together and without supporting bars
constitute a plate capable of resisting a higher wind pressure than
a plate of the same size composed of a solid mass of such glass.
These prism plates must also, if used for
window lights, be wind and water tight. Electro-glazing accomplishes
this result, for the deposited metal becomes so intimately connected
with the edges of the prism lenses that the copper and glass become,
as it were, welded together, neither wind nor water being able to
penetrate between the frame and the prism lens. This is found by
actual experience to be true under all conditions of the widest
variation in temperatures, from the extreme heat of summer to the
extreme cold of winter. This is not true of other methods by means
of which such prism lenses might be united. Thus it happens that
where such prism lenses are glazed by means of lead, zinc, brass
or other such frames, the varying contraction and expansion of the
prism lenses and the frame result necessarily in loosening the
cement. No cement work can possibly be permanently effective, and
the same cause which renders the cement necessary makes it perishable.
A thin frame, with a limited amount of cement, may hold the prism
lenses in position for a short time, or until the contractor can
deliver his job and get his money, but it is certain soon to
disintegrate and the lenses to loosen. All these difficulties are
obviated by the use of electro-glazing.
In the use of prisms it is desirable to get
the greatest possible prism area, because the opaque portions of
the frame or the plane surface of glass about the prism surface
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