A New or Improved Method of Applying to Metallic Mirrors, Images, Signs, and the like, which Ordinarily remain Invisible, but become Visible by Reflected Luminous Rays.
Year: 1889

page_text: COMPLETE SPECIFICATION.
A New or Improved Method of Applying to Metallic Mirrors,
Images, Signs, and the like, which Ordinarily remain Invisible,
but become Visible by Reflected Luminous Rays.
We, PHILIPP ROSENTHAL, Merchant, and CARL WEGENER, Engineer, of Moscow,
Russia, do hereby declare the nature of this invention and in what manner the same
is to be performed to be particularly described and ascertained in and by the following
statement:
Our invention relates to a new or improved method of applying images, signs, and
the like, to metallic mirrors in such a way that in the ordinary use of the mirror these
images, signs and the like, are invisible and do not prejudicially influence its good
quality, but when the mirror is exposed to the light, and luminous rays are reflected
from it onto a surface or an object, those images, signs, and the like become visible on
the said surface or object.
The improved metallic mirror has therefore the double purpose:-
1. To serve as an ordinary mirror.
2. To be capable of forming at any time by means of reflected luminous rays an
image which is ordinarily invisible.
Mirrors according to this invention are manufactured in the following manner :-
Any suitable kind of metal may be used as for instance iron, or steel and may be
wrought to any desired plane or curved form. The surface of the mirror is then
hardened and polished. To the polished surface of the mirror is then applied an
embossed or sunk image, whereupon the surface of the mirror is polished again to
such a degree, that in looking in the mirror the image will no longer be visible and
the effect of the ordinary reflection will not be prejudicially influenced.
By the alteration of the structure of the metal caused by the application of the
image, sign or the like, and the subsequent polishing, the image becomes invisible
and re-appears when it is exposed to the light and reflected onto another surface.
The images, signs or the like may be produced on the polished metallic mirror by
etching, engraving, pressing or by any other suitable operation, for the execution of
which, use may be made of a sand blast, a graver, a stamp, or of any other suitable
means. By grinding and subsequent polishing or by any other operation usually
employed for polishing metallic objects, the image is made invisible to such a degree
that it will not prejudicially influence the mirror and will be formed on another
surface than that of the mirror only when the luminous rays are reflected by the
mirror onto the said surface.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
The hereinbefore described method of applying to a metallic mirror, images, signs
or the like, which do not prejudicially influence the mirror but which are rendered
visible by reflecting luminous rays onto another surface than that of the mirror, the
said method comprising the application of the images, signs, or the like to the
polished plane or curved surface of a metallic mirror by etching, engraving, pressing
or other suitable operation and the rendering of the images or the like invisible
to direct inspection by means of a second polishing which may be effected by grinding
and burnishing the surface of the mirror, substantially as set forth.
Datad this 9th day of Inly 1800