AN IMPROVED WRITING SLATE AND METHOD OF MANUFACTURING THE SAME
Year: 1884

page_text: 13
I, ALEXANDER MELVILLE CLARK, of the firm of A. M. and Wm. Clark, of 53,
Chancery Lane, in the County of Middlesex, Fellow of the Institute of Patent
Agents, do hereby declare the nature of the said Invention for AN IMPROVED
WRITING SLATE AND METHOD OF MANUFACTURING THE SAME a communication
to me from abroad by Philipp Wenzel, of Mainz in the Empire of Germany,
through his Agents, Wirth and Company, of Frankfort-on-the-Main, to be as
follows:-
Modern oculists and other authorities have recognized the necessity of white
School slates, which permit of writing upon them in black lines, for children's use,
White school slates have consequently already been made of porcelain and other
materials which however on the one hand are breakable and on the other hand
are too expensive to admit of their general introduction.
This invention consists in a white writing "slate" which is neither breakable
nor expensive, which can be written on with black lead pencil and which can be
readily cleaned off with a sponge. The process of manufacture of the “slate” is
as follows:-
A piece of sheet iron cut to the required size of the "slate" is uniformly coated
on both sides with pulverized white enamel, in the form of paste. As soon as the
coating is dry, the "slate" is subjected to a red heat in a muffle whereby the
enamel is melted and caused to adhere firmly to the metallic foundation.
Tho "slate" thus enamelled is, however, as smooth as glass and consequently
does not admit of being marked on by lead pencil. In order to roughen the
surface or give it a "tooth" which will enable it to receive the lead pencil the
slate" is immersed several times in a dilute solution of bydrofluoric acid whereby
a uniform and delicate matt surface is imparted which is admirably adapted for
writing upon with lead pencil, and which may be easily cleaned off again with a
moist sponge. If it be desired to rule indelible lines it is only necessary to draw
a sharp iron point lightly across the slate whereby grey lines are produced which
cannot be effaced by rubbing or washing.

page_text: VAD
"
1, ALEXANDER MELVILLE CLARK, of the firm of A. M. and Wm. Clark, of 53,
Chancery Lane, in the County of Middlesex, Fellow of the Institute of Patent
Agents, do hereby declare the nature of the said Invention for "AN IMPROVED
WRITING SLATE AND METHOD OF MANUFACTURING THE SAME (a communication
to me from abroad by Philipp Wenzel, of Mainz, in the Empire of Germany
through his Agents, Wirth and Company of Frankfort on the Main) and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
Modern oculists and other authorities have recognized the necessity of white
School alates, which permit of writing upon them in black lines, for children's use.
White school slates have consequently already been made of porcelain and other
materials which however on the one hand are breakable and on the other hand are
too expensive to admit of their general introduction.
This Invention consists in a white writing "slate" which is neither breakable nor
expensive, which can be written on with black lead pencil and which can be
readily cleaned off with a sponge. The process of manufacture of the "slate " is as
follows
A piece of sheet iron cut to the required size of the "slate" is uniformly coated
on both sides with pulverized white enamel, in the form of paste. As soon as the
coating is dry, the "slate" is subjected to a red heat in a muffle whereby the
enamel is melted and caused to adhere firmly to the metallic foundation.
The "slate "thus enamelled is, however, as smooth as glass and consequently
does not admit of being marked on by lead pencil. In order to roughen the surface
or give it a "tooth" which will enable it to receive the lead pencil, the "slate" is
immersed several times in a dilute solution of hydrofluoric acid whereby a uniform
and delicate matt surface is imparted which is admirably adapted for writing upon
with lead pencil, and which may be casily cleaned off again with a moist sponge.
If it be desired to rule indelible lines it is only necessary to draw a sharp iron point
lightly across the slate whereby grey lines are produced which cannot be effaced
by rubbing or washing.
Having now particularly described and ascertained the nature of the said
Invention and in what manner the same is to be performed, I declare that what
I claim is
"
The manufacture of a white unbreakable writing slate by conting a sheet iron
plate with enamel and roughening or imparting a "tooth to the latter by means
of repeated immersions in dilute hydrofluoric acid as specified.
Dth IL
1005