Improvements in Looking Glasses and Daylight Reflectors, and in the Method of Manufacturing the same.
Year: 1894

page_text: Date of Application, 21st Mar., 1894
Complete Specification Left, 19th Dec., 1894-Accepted, 21st Mar., 1895
VIDIONAL STE
Improvements in Looking Glasses and Daylight Reflectors, and in
the Method of Manufacturing the same.
A communication to me from ALFRED Rost, of Wiesen, near Halbstadt,
Bohemia, Merchant.
I, EDMUND EDWARDS, of the Firm of Edwards and Co., Patent Agents and
Engineers, of 65 and 66, Chancery Lane, in the County of Middlesex, do hereby
declare the nature of this invention to be as follows:-
This invention relates to an improved method of manufacturing the coating of
looking-glasses by the wet process, from silver and platinum, and also to the
application of the said method for the production of platinum-silver-coated
looking-glasses of every kind and description and for all purposes of use, more
particularly for day-light reflectors, and, finally, to the method of manufacturing
transparent looking-glasses and day-light reflectors by employing either the new
coating of silver and platinum, or the known coating of nitrate of silver.
The looking-glasses having a coating of platinum and silver unite in them all the
advantages of other looking-glasses hitherto known and used; whilst they are
much superior to all other looking-glasses in respect to their extraordinary
resistance against all atmospheric influences, and also against the chemical action
of acids, gases, vapours, and the like; they further have the particular quality
that they can be made with any desired degree of transparency or translucence,
just the same as the known silver looking-glasses.
The transparent looking-glasses with a coating of platinum-silver, or silver,
reflect excellently from one side and act as mirrors, but at the same time they
allow the light to pass. Such looking-glasses, accordingly, may be employed for
admitting light into rooms, into which it is desired that persons outside shall
not be able to see through the glass; or they may be employed where persons upon
one side of the glass wish to look through the same without being observed by
those outside.
In the manufacture of ordinary looking-glasses, flat plates of glass are used, but
for day-light reflectors corrugated plates are preferred. In all cases, where the
looking-glass is made transparent or translucent, the coating of platinum and
silver, or of nitrate of silver, is covered by a fine transparent coating of weather-
proof varnish, and further, if necessary, with a transparent plate of glass, and in
some cases a trellis or wire-work of wide meshes may be employed.
The new method of manufacturing the coating of platinum and silver by the wet
process is as follows:-
A solution is prepared of a compound of nitrate of silver and platinum-salts,
which, through the agency of reducing means, is applied to the glass. To prepare
the compound salt before mentioned, an alloy of platinum and silver is, for a con-
siderable time, boiled in concentrated nitric acid; the platinum which has not
entered into solution by the said boiling process, is separated by filtration, and then
the pure solution is concentrated by evaporation up to the state of crystallization.
From the crystals thus obtained, immediately previous to their application, the
following two solutions are then prepared, viz. :-
1. The proper coating-fluid, made by dissolving 1 part by weight of the crystals
already described in 10 parts by weight of distilled water.

page_text: 2. The neutralizing fluid, being exactly the same as that specified under 1, but
of less quantity.
To
To the solution described above under (1), is added ammonia under constant
agitation; the said addition being finally made by drops, until the sediment, which
had first been formed, has been dissolved again and the fluid becomes clear.
obtain this, ammonia must be added in excess, but this being objectionable in the
following process, sufficient of the neutralizing fluid before described is added,
until the smell of anmenia is no longer perceptible, and the fluid is again muddy.
After this are added to one part by weight of the crystals employed in preparing
the solution before stated under (1), one hundred parts by weight of distilled
water, and filtering is continued until the fluid is obtained completely clear. The
coating fluid is now ready for use, but it cannot be preserved, because, after
keeping it during a period of some extent, it will again become muddy by decom-
position, the platinum being deposited upon the bottom of the vessel in the form of
a lemon-colored powder.
To prepare the reduction-fluid, 0.8 parts by weight of Seiguette-salt are boiled
with 384 parts by weight of distilled water, and to the boiling solution is gradually
added a solution of 1 to 3 parts by weight of nitrate of silver in 8 to 10 parts by
weight of distilled water.
If it is desired to obtain opaque platinum-silver looking glasses of particular
beauty and whiteness, beside the coating-fluid proper, an additional fluid is
prepared, which is obtained by boiling 1-8 gr. of Seignette-salt in 990 ccm. of
water; to the boiling mass is added a solution of 1 gr. of nitrate of silver in 8 ccm.
of water.
Another modification in manufacturing opaque looking glasses consists in
diluting the coating-fluid above described under (1), with 200 parts by weight
of water with 1 part by weight of the crystals employed in preparing the
solution (1).
The particular reduction-fluid before described is not absolutely essential in
the process of the present invention; as other reducing agents which are generally
known, may be employed alone or in combination with each other, the preference
of one or the other of such reducing agents will depend upon the particular
object to be obtained, viz. the greater or less quantity of platinum desired t
be deposited and, consequently, the desired degree of opacity or transparency
to be produced, and further upon the desired shade of color of the looking-
glass, and of the extent of time within which the operation is desired to be
completed.
The operation of forming the coating or deposition on the glass plate is effected
as follows:
A mixture is prepared of equal volumes of the coating fluid and the
reducing-fluid above described, or 3 volumes of the coating fluid may be mixed
with one volume of the reducing-fluid and 2 volumes of the additional fluid before
described the mixture being prepared by stirring or shaking the fluids in a common
vessel; the said mixture is then poured upon the glass plate, which has been
previously carefully cleaned and arranged in horizontal position; or the glass
plate may be submerged in the mixture, as usual in the manufacture of looking-
glasses. The operation of coating the glass should be carried on at a temperature
of at least 25° Centigrade, and the fluids employed should be kept at least at the
same temperature.
In coating the opaque looking-glasses ordinarily in use, attention has to be paid
to obtaining the layer of platinum and silver, or of nitrate of silver, of great
density, and for this purpose the operation of pouring the coating-fluid on the glass
plate has to be repeated once or several times. But in the manufacture of trans-
parent looking-glasses, the formation of the metallic deposit on the contrary, must
be interrupted at the proper time by drawing off the coating fluid or by removing
the glass plate from the bath, after which the said plate is carefully cleaned by
rinsing it with distilled water.
At first, before practice has determined the exact time during which the

page_text: operation of forming the transparent coating must be carried on, an approximate
scale for observing the degree of translucence may be obtained by spreading a sheet
of white paper below the glass plate.
It is essential that the coating, whether of silver or of platinum and silver,
should be distributed as uniformly as possible, as clear as possible, and not of too
dark color, but nevertheless of sufficient density to constitute a fine and good
looking-glass, which allows the light to penetrate and through which one may look
from behind the glass.
As soon as the fresh coating on the glass plate has been rinsed with distilled
water, the glass is put upright for drying, and, when completely dry, the coated
side is covered with a fine colorless varnish which may be poured over the surface
or applied by dipping the glass plate into a bath of such varnish.
When the said
coating of varnish is completely dry, a transparent glass plate of corresponding
thickness is laid over it and the whole then put into a frame; it is preferable to
cement the mirror in its frame in order to prevent dust from entering between the
two plates.
The transparent looking-glasses and daylight reflectors of this kind may be
applied everywhere in the place of other looking-glasses and daylight reflectors,
and where it is desired that the light should penetrate the glass, or where the
person behind the glass desires to look through it, without being seen from without.
The application accordingly is particularly useful for the windows of shops, stores,
warehouses and the like, or to fill the back of casings in shops and the like, also for
panels and panes of doors in private or ante-rooms, bath-rooms and any other
places, into which it is desired that daylight should enter, whilst persons outside
are not able to look in, or where persons within desire to look out through the
glass, without being seen from the outside.
Dated this 20th day of March 1894.
EDWARDS & Co.,
65 and 66, Chancery Lane, London, Agents for the Applicant.
Improvements in Looking Glasses and Daylight Renectors, anu
the Method of Manufacturing the same.
A communication to me from ALFRED ROST, of Wiesen, near Halbstadt,
Bohemia, Merchant.
In
1, EDMUND EDWARDS, of the Firm of Edwards and Co., Patent Agents and
Engineers, of 65 and 66, Chancery Lane, in the County of Middlesex, 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, that is to say:―
This invention relates to an improved method of manufacturing the coating of
looking glasses by the wet process, from silver and platinum, and also to the
application of the said method for the production of platinum silver-coated looking
glasses of every kind and description and for all purposes of use, more particularly
for daylight reflectors, and, finally, to the method of manufacturing transparent
looking glasses and daylight reflectors by employing either the new coating of
silver and platinum, or the known coating of nitrate of silver.
The looking-glasses having a coating of platinum and silver unite in them all the
advantages of other looking-glasses hitherto known and used; whilst they are
much superior to all other looking-glasses in respect to their extraordinary
resistance against all atmospheric influences, and also against the chemical action

page_text: of acids gases, vapours, and the like; they further have the particular quality
that they can be made with auy desired degree of transparency or translucence,
just the same as the well-known silver looking glasses.
The transparent looking-glasses with a coating of platinum-silver, or silver,
reflect excellently from one side and act as mirrors but at the same time they
allow the light to pass. Such looking-glasses, accordingly, may be employed for
admitting light into rooms, into which it is desired that persons outside shall not
be able to see through the glass; or they may be employed where persons upon
one side of the glass wish to look through the same without being observed by
those outside.
In the manufacture of ordinary looking-glasses, flat plates of glass are used, but
for daylight reflectors corrugated plates are preferred. In all cases, where the
looking-glass is made transparent or translucent, the coating of platinum and
silver, or of nitrate of silver, is covered by a fine transparent coating of weather-
proof varnish, and further, if necessary, with a transparent plate of glass, and in
some cases a trellis or wire-work of wide meshes may be employed.
The new method of manufacturing the coating of platinum and silver by the wet
process is as follows:-
A solution is prepared of a compound of nitrate of silver and platinum-salts,
which, through the agency of reducing means, is applied to the glass. To prepare
the compound salt belore mentioned, an alloy of platinum and silver is, for a con-
siderable time, boiled in concentrated nitric acid; the platinum which has not
entered into solution by the said boiling process, is separated by filtration, and then
the pure solution is concentrated by evaporation up to the state of crystallization.
From the crystals thus obtained, immediately previous to their application, the two
following solutions are then prepared riz.:-
1. The proper coating fluid, made by dissolving 1 part by weight of the
crystals already described in 10 parts by weight of distilled water.
2. The neutralizing fluid, being exactly the same as that specified under (1),
but of less quantity.
To the solution described above under (1), is added ammonia water under
constant agitation; the said addition being finally made by drops, until the
sediment, which had first been formed, has been dissolved again and the fluid
becomes clear. To obtain this, ammonia must be added in excess, but this being
bjectionable in the following process, sufficient of the neutralizing fluid before
described is added, until the smell of ammonia is no longer perceptible, and the
fluid is again muddy. After this are added to one part by weight of the crystals
employed in preparing the solution before stated under (1), one hundred parts by
weight of distilled water, and filtering is continued until the fluil is obtained
completely clear. The coating fluid is now ready for use, but it cannot be
preserved, bernuse, after keeping it during period of some extent, it will again
come muddy by decomposition, the platinum being deposited upon the bottom of
the vessel in the form of a lemon coloured powder.
1
To prepare the reducing fluid, 0-8 parts by weight of Seignette salt are boiled
with 384 parts by weight of distilled water, and to the boiling solution is gradually
added a solution of one to three parts by weight of nitrate of silver in 8 to 10 parts
by weight of distilled water.
If it is desired to obtain opaque platinum-silver looking-glasses of particular
beauty and whiteness, beside the coating-fluid proper, an additional fluid is
prepared which is obtained by boiling 1-8 gr. of Seignette salt in 990 ccm. of
water; to the boiling mass is added a solution of 1 gr. of nitrate of silver in
8 ecin, of water.
Another modification in manufacturing opaque looking-glasses consists in
diluting the coating fluid above described under (1), with 200 parts by weight
of water with one part by weight of the crystals employed in preparing the
solution (1).
The particular reduction fluid before described is not absolutely essential in the

page_text: process of the present invention; as other reducing agents which are generally
known, may be employed alone or in combination with each other, the preference
of one or the other of such reducing agents will depend upon the particular object
to be obtained, ei. the greater or less quantity of platinum desired to be
deposited and, consequently, the desired degree of opicity or transparency to be
produced, and further upon the desired shade of colour of the looking-glass, and
the extent of time within which the operation is desired to be completed.
The operation of forming the coating or deposition on the glass plate is effected
as follows: A mixture is prepared of equal volumes of the coating fluid and the
reducing fluid above describe 1, or three volumes of the coating fluid may be mixed
with one volume of the reducing-Huid, and two volumes of the additional fluid
before described, the mixture being prepared by stirring or shaking the fluids in a
common vessel; the said mixture is then poured upon the glass plate, which has
been previously carefully cleaned and arranged in horizontal position; or the glass
plate may be submerged in the mixture, as usual in the manufacture of looking-
glasses. The operation of coating the glass should be carried on at a temperature
of at least 25° Centigrade, and the fluids employed should be kept at least at the
same temperature.
For the manufacture of transparent looking-glasses and daylight reflectors with
a coating of nitrate of silver, the well-known fluids serving for the making of
common silver looking-glasses are used.
That is to say, first, about 10 grammes of crystallized nitrate of silver are
dissolved in 50 cubic centimetres of distilled water; then pure liquid ammonia is
gradually added until it becomes clear. To this solution is added distilled water,
until the solution becomes slightly turbid.
The solution is filled up with distilled water to 1 litre; and is allowed to rest
until it has become quite clear.
Second; reducing fluid.
20 grammes Seiguette" salt (tartrate of kalium-natrium) and 20 grammes of
white candy-sugar are dissolved in 200 cubic centimetres of distilled water; to this
solution is added a solution of 4 grammes of nitrate of silver in 20 cubic centi-
metres of distilled water; then the whole is well shaken and heated up to ebullition,
in which state the fluid remains for half an hour; the solution is then taken from
the fire and at once mixed with so much cold water that 1 litre of fluid is formed.
After the shaking, filtering takes place.
For coating the glass, a volume of the first solution of silver is mixed with an
equal volume of the second, or reducing fluid, and the mixture as quickly as
possible poured upon the glass plates upon the coating tables.
In coating the opaque looking-glasses ordinarily in use, attention should be paid
to obtaining the layer of platinum and silver, or of nitrate of silver, of great
density, and for this purpose the operation of pouring the coating-fluid on the
glass plate has to be repeated once or several times. But in the manufacture of
transparent looking-glasses, the formation of the metallic deposit, on the contrary,
must be interrupted at the proper time by drawing off the coating fluid or by
removing the glass plate from the bath, after which the said plate is carefully
cleaned by rinsing it with distilled water.
At first, before practice has determined the exact time during which the
operation of forming the transparent coating must be carried on, an approximate
scale for observing the degree of translucence may be obtained by spreading a
sheet of white paper below the glass plate.
It is essential that the coating, whether of silver or of platinum and silver,
should be distributed as uniformly as possible, as clear as possible, and not of too
dark colour, but nevertheless of sufficient density to constitute a fine and good
looking-glass, which allows the light to penetrate and through which one may look
from behind the glass.
As soon as the fresh coating on the glass plate has been rinsed with distilled
water, the glass is put upright for drying, and when completely dry, the coated

page_text: side is covered with a fine colourless varnish which may be poured over the
When
surface or applied by dipping the glass plate into a bath of such varnish.
the said coating of varnish is completely dry, a transparent glass plate of corre-
sponding thickness is laid over it and the whole then put in a frame. It is
preferable to cement the mirror in the frame, in order to prevent dust from entering
between the two plates.
The transparent looking glasses and daylight reflectors of this kind may be
applied everywhere in the place of other looking-glasses and daylight reflectors,
and where it is desired that the light should penetrate the glass, or where the
person behind the glass desires to look through it, without being seen from without.
The application, accordingly, is particularly useful for the windows of shops,
stores, warehouses and the like, or to fill the back of casings in shops and the like,
also for panels and panes of doors in private or ante-rooms, bath-rooms and any
other places, into which it is desired that daylight should enter, whilst persons
outside are not able to look in, or where persons within desire to look out through
the glass, without being seen from the outside.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. The improved method of manufacturing the coating, containing platinum and
silver, for looking-glasses, from a compound of platinum and oitrate of silver by
the aid of reducing means; as also the application of such coating for manu-
facturing looking-glasses of every kind, and also transparent mirrors and daylight
reflectors substantially as described.
2. The method of manufacturing transparent looking-glasses and daylight
reflectors by a coating of nitrate of silver, substantially as described.
Dated this 18th day of December 1894.
EDWARDS & Co.,
65 and 66, Chancery Lane, London, Agents for the Applicant.