glass plate, the film being exposed to light through the back of the
glass, and thus rendered insoluble and tightly cemented to the surface;
this film serving as a basis for the second sensitive coating, that
was afterward impressed by the negative. This double treatment is now
definitely abandoned in most Lichtdruck establishments, and, instead, a
preliminary coating of soluble silicate and albumen dissolved in water
is used.

Herr Loewy's method and formula are as follows: The glass plate is
cleaned, and coated with--

Soluble glass. 3 parts.
White of egg. 7 "
Water. 9 to 10 "

The soluble glass must be free from caustic potash. The mixture, which
must be used fresh, is carefully filtered, and spread evenly over the
previously cleaned glass plate. The superfluous liquid is flowed off,
and the film dried either spontaneously or by slightly warming. The film
is generally dry in a few minutes, when it is rinsed with water, and
again dried; at this stage the plate bears an open, porous film,
slightly opalescent--so slight, however, as only to be observed by an
experienced eye.

_Application of the Sensitive Film_.--We now come to the second stage of
the process, the application of a film of bichromated gelatine to the
plate.

Herr Loewy's formula is as follows: