IMPROVEMENTS IN AND RELATING TO POSTAGE, REVENUE, AND OTHER STAMPS
Year: 1877

page_text: PROVISIONAL SPECIFICATION left by William Robert Lake at the Office
of the Commissioners of Patents on the 1st October 1877. A communication
from abroad by James Sangster, George H. Dunbar, and Robert Dunbar, all of
Buffalo, New York, United States of America.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. "IMPROVEMENTS IN AND RELATING TO POSTAGE,
REVENUE, AND OTHER STAMPS." [A communication from abroad by James Sangster,
George H. Dunbar, and Robert Dunbar, all of Buffalo, New York, United States
of America.]
The object of this Invention is to produce upon portions of a stamp design a
chemical change in the oily or other material which holds the particles of the
coloring matter of the ink together, so that when an attempt is made to wash or
otherwise erase the cancelling ink from the stamp for fraudulent re-use, the parts
so changed will wash out and expose the attempt by destroying the appearance of
the stamp.
The said Invention comprises a postage or other stamp, having lines, dots, or
characters, ruled or otherwise, placed upon its surface, composed of a material that
unites with and changes the oily, fatty, or resinous matter in the ink, thereby
forming a soapy compound, or otherwise rendering it soluble in water or other
liquids in such lines or dots without seriously injuring the appearance of the coloring
matter therein. The soluble lines are put on after the stamp is printed.
There are many of the alkalies that may be used for this purpose, but in practice
I find that caustic soda is very advantageous. It ceases to be caustic in a short
time after being put on, as it rapidly absorbs carbonic acid from the air and becomes
carbonate of soda, after which it remains without change, and does not readily
absorb water or become wet from the atmosphere like caustic potash, or its
equivalent. The caustic soda may be used in combination with many of the
alkalies in such proportions that the compound will be strong enough for the pur-
pose.
In some instances I use a solution of caustic soda and borax, also caustic potash,
carbonate of ammonia, cyanide of potassium, and other alkaline solutions, but a
solution of caustic soda and water having a specific gravity of 1.356, or there-

page_text: abouts, answers a good purpose, though it may be further diluted with water and
work well, according to the coarseness or fineness of the lines, very fine lines
requiring a stronger solution than coarse lines.
The depth at which the solution penetrates the ink or paper may also be regu-
lated by the width of the lines, as coarse lines hold a greater quantity of the
solution, and will penetrate deeper into the ink and paper than fine lines, which do
not hold so much.
The stamp may be ruled or otherwise impressed with the solution on either side,
but the lines or clots should be coarse enough to hold sufficient material to pass
through the paper so as to reach and act upon the material in the ink as herein-
before mentioned. When such lines are placed on the face of the stamp it is not
necessary that the solution should pass through the paper, but only far enough to
act on the ink, consequently they may be made finer or sufficiently narrow to pro-
duce the desired effect.
The said Invention also comprises a process of preparing the surface of postage
or other stamps for the reception of the desired design, and which consists in
covering all, or a portion of the surface, with a uniform coating, or with ruled or
printed lines or dots, in au ink composed essentially of dextrine, or gelatine, sesqui-
chloride of iron, tartaric acid, and water, in about the proportions stated, or other
equivalent compound, which is insoluble in water after it becomes dry while kept
in the dark, so that the paper may be damped and the desired design printed
thereon with ordinary printing ink without disturbing the previously printed
surface lines or dots, which are afterwards. made soluble in water either by
exposure to the action of light or immersion in a bath of tartaric acid or its
equivalent.