The coating of the glass takes place immediately afterward in a dark
room; the coated sheets are then subjected to a heat of 50 deg. or 60 deg. C.
(120 deg. to 140 deg. Fahr.) in a small hot chamber, where they are laid one
after the other on a wire grating situated 35 centimeters above the
bottom. Care should be taken not to introduce the glass under treatment
into the hot chamber before the required degree of heat has been
obtained. A few seconds are sufficient to dry each sheet, and the wire
grating should be large enough to allow of the dried glass being laid in
rows, on one side where the heat is less intense. For the reproduction
of the pictures or images a photographic copying frame of the size of
the original is used. A stained glass window being for greater security
generally divided into different panels, the size of one panel is seldom
more than one square meter. If the picture to be reproduced should be
larger in size than any available copying frame, the prepared glass
sheets are laid between two large sheets of plate-glass, and part after
part is proceeded with, by sliding the original between the two sheets.
A photographic copying frame, however, is always preferable, as it
presses the glass sheets better against the original. The original
drawing is laid fiat on the glass of the frame. The lines where the lead
is to connect the respective sheets of glass are marked on the drawing
with blue or red pencil. The prepared sheets of glass are then placed
one after the other on the original in their respective places, so that
the coated side comes in contact with the original. The frame is then
closed. It should be borne in mind that the latter operations must be
performed in the dark room. The closed frame is now exposed to light. If
the operations are performed outdoors, the frame is laid flat, so that
the light falls directly on it; if indoors, the frame is placed inclined
behind a window, so that it may receive the light in front. The time
necessary for exposing the frame depends upon the light and the
temperature; for instance, if the weather is fine and cloudless and the