AN IMPROVED PROCESS OF PRODUCING DESIGNS UPON GLASS AND OTHER SURFACES
Year: 1880

page_text: A com-
PROVISIONAL SPECIFICATION left by Alexander Melville Clark at the
Office of the Commissioners of Patents on the 29th July 1880.
munication from abroad by Dominique Scotellari, of Paris, France.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of
Middlesex, Patent Agent. "AN IMPROVED PROCESS OF PRODUCING DESIGNS
UPON GLASS AND OTHER SURFACES." [A communication from abroad by Dominique
Scotellari, of Paris, France.]
This Invention relates to a process of producing designs on flint and other glass and
on enamels, porcelains, and the like, with the aid of light, such as for the production
of artistic stained glass, whereby I am enabled to produce on glass, for example,
a partly clear and partly matt design, as in engraving with hydrofluoric acid, but
having much greater delicacy of detail than can be obtained by the latter method,
This improved result is due to the intervention of the action of light, whereby the
nature of a preparation or coating previously applied on the surface to be orna-
mented is modified, this modification of its nature taking place only in certain
parts, and having for effect to modify or retain, as the case may be, the adhesive or
sticky property of this composition or coating.
I first coat the surface to be ornamented with what is called enamel collodion.
For this coating I employ by preference the following composition :-
It must be understood that I do not limit myself to these proportions, which are
subject to variation according to the variable conditions of temperature and other
circumstances.
To the above ingredients I add 18 cubic centimetres (1·098 cubic inches), of a
saturated solution of bichromate of ammonia or potash.
In some cases the dose of bichromate may be increased. As this coating is
This done,
sensitive to light, the operation should be performed in the dark room.
the image is printed on the surface from a positive, either by contact in the printing
After a few minutes
frame, or by projection in an enlarging or reducing camera.
exposure the image is developed in the dark room by the application of enamel or

page_text: glass powder with a badger hair brush until the image appears with the desired
sharpness and intensity; when the development is finished I fix by firing in an
oven at a high temperature.
In the case of large plates, instead of making the powdered vitrifiable colors
adhere by means of a brush, I operate as follows:-The glass plate on which the
image has been produced is made to form one of the sides of a box in which
the enamel powder is placed. All the sides of this box being transparent, the
charging the plate with enamel powder can be easily watched, and when sufficiently
charged the adhesive deposit is allowed to, remain at least 3 days, and is then
immersed for 12 hours in a bath of plain water, which removes the yellowish
coating colored by the bichromate, which would prejudice the firing or would
leave on the plate a greenish yellow tint.
This washing having removed a part of the flux of the enamel, it is replaced (when
the plate is dry) by a solution of borax at 10 per cent., by applying with a badger
hair brush over the whole surface a coat of a solution of 4 parts of spirit of
turpentine and 1 part of fat spirit. In this state the plate is colored by means of
metallic oxides and salts, silicates, and enamels employed in painting on glass,
which are applied by means of spirit on the right side, or preferably with gum on
the back surface of the plate. Water or gum colors are applied to heighten the
effect, and the whole is fixed by firing at a high temperature.