IMPROVEMENTS IN COATING GLASS WITH SILVER FOR LOOKING GLASSES AND OTHER USES
Year: 1843

page_text: TOMAS
TO ALL TO WHOM HESE PRESENTS SHALL COME, 1,
DRAYTON, of Brighton, in the County of Sussex, Gentleman, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Letters Patent under the Great Seal of Great Britain, bearing date at West-
minster, the Twenty-fifth day of November, in the seventh year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Thomas Drayton, Her especial licence, full power, sole privilege and authority,
that I, the said Thomas Drayton, my exors, admors, and assigns, or such others
as I, the said Thomas Drayton, my exors, admors, or assigns, should at any
time agree with, and no others, from time to time and at all times during the
term of years therein expressed, should and lawfully might make, use, exercise,
and vend, within England, Wales, and the Town of Berwick-upon-Tweed, my
Invention of "IMPROVEMENTS IN COATING GLASS WITH SILVER FOR LOOKING GLASSES
AND OTHER USES;" in which said Letters Patent is contained a proviso that
I, the said Thomas Drayton, shall cause a particular description of the nature
of my said Invention, and in what manner the same is to be performed, to
he inrolled in Her said Majesty's High Court of Chancery within six calendar
months next and immediately after the date of the said in part recited Letters
Patent, as in and by the same, reference being thereunto had, will more fully
and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Thomas Drayton, do hereby declare that the nature of my said Invention, and

page_text: the manner in which the same is to be performed, are fully described and
ascertained in and by the following statement thereof (that is to say):-
The Invention consists in causing silver to be deposited on to glass from a
solution of silver, by deoxidizing the oxide of silver in solution in such a manner
that the precipitate of silver will adhere to the glass without any previous
coating of the glass with metallic or other substances. And in order that the
Invention may be fully understood and readily carried into effect, I will pro-
ceed to describe the means pursued by me. I would first remark that the
Invention is applicable in the manufacture of looking glass and in other cases
where it is desired to have glass coated with silver. It is well known that in
silvering glass in the making of looking glasses, as at present practised by the
use of quicksilver, the process is very unhealthy; and it is an important feature
in this Invention that this injurious and unhealthy process is dispensed with,
and the glass is coated with silver deposited from a solution of silver, giving a
more beneficial result and a very beautiful effect. My process is as follows:-
I take at the rate of one ounce of coarsely pulverized nitrate of silver,-that
which I generally employ is the lunar caustic of commerce, and mix it with
half an ounce of spirits of hartshorn; to these I add two ounces of water, and
let the mixture stand twenty-four hours; then filter the same (preserving the
deposit on the filter, which is silver). I then add to the filtered liquor three
ounces by measure of spirit. I prefer spirits of wine at about sixty degrees
above proof, or naptha. I then add from twenty to thirty drops of oil of cassia.
The mixture after having remained for five or six hours is ready for use, and I
have found it desirable not to keep it more than twenty-four hours after the oil
of cassia has been added thereto; but the mixture, before the addition of the
oil of cassia, appears to improve by keeping. When the proper time has
elapsed after the addition of the oil of cassia, the mixture is to be applied in
the following manner :-The glass intended to be silvered having been placed
in a horizontal position, I form a projecting fence at all sides with putty or
other suitable material, so that the liquid can cover to the depth of from one
eighth to a quarter of an inch the whole surface of the glass which is to be
silvered. The surface of the glass should be clean and polished before pouring
on the liquor above described; and when the liquor has been run on to the
surface of the glass, a few drops, say from six to twelve, of a mixture con-
sisting of one part by measure of oil of cloves to three parts of spirits of wine,
are to be dropped at different places into the liquor on the glass, such six to
twelve drops of diluted oil of cloves being the proper quantity for the quantity
of liquor above mentioned, or the oil of cloves may be mixed with the liquor
just before bringing the same in contact with the glass to be silvered. It

page_text: should be stated that the more oil of cloves used the more quickly does the
deposit of silver take place; but I prefer that the process of precipitation or
deposition should take about two hours. This, a workman after a little
practice, will readily adjust. And it is important to call attention to the
circumstance, that the articles employed as commercially manufactured fre-
quently differ in strength and purity, the quantities requisite for carrying on
the process most favourably will consequently vary; but a careful workman,
aided by the observations herein made, will, after a little practice, quickly be able
to judge of the qualities of the different materials, and by testing his mixtures
thereof on portions of glass he will be enabled to see when the best result from
given materials has been obtained. As also different samples of the oil of
cassia purchased at different times differ very much in quality, I have found
that it is desirable to test each quantity purchased by ascertaining whether it
will mix with a solution of silver in hartshorn, water, and spirit, as above
described; and if I find that it mixes readily, then I know it will be proper
for the purpose; but if I find that it becomes flakey, I allow it to stand after
mixing, and afterwards filter the mixture. I would state, that although I have
spoken of applying the liquor to the glass when in a horizontal position, it may
be applied when the glass is in other positions, provided the liquor be kept in
contact with the surface of the glass. I have found that if the glass to be
coated be placed in an inclined or even in a vertical position, and the surface
covered over, leaving a narrow space for the liquor between the surface of the
glass and the cover, the cover fitting close, then by simply using spirit without
water in the mixture the object will be accomplished; and it is advantageous to
use a close cover of wood were convenient, in order to prevent the loss of
spirits of wine by evaporation. I have found that the use of a small quantity
of the oil of thyme or of carraways varies the color of the silver, and will be
useful in some cases for that purpose. The liquor, having been used, is poured
off, and allowed to stand for some time, say three or four days, in a close vessel,
as it still contains silver, and may again be used by filtering it, and adding fresh
ingredients, according to the quantities of the materials used up. As far as my
experience goes, I have found that about eighteen grains of nitrate of silver
are used for each square foot of glass. The quantity of spirit used varies some-
what, as its evaporation depends upon temperature and the duration of the
process. A very little practice will enable the workman to judge of the
quantities consumed. As soon as the silver on the glass is perfectly dry, I
varnish the back of the silver, and I prefer for such purpose bees' wax and
tallow, in about equal quantities melted together.
Having thus described the nature of the Invention, and the means pursued

page_text: by me in performing the same, I further say, that I do not confine myself to
the precise details herein described, provided the peculiar character of the
Invention be retained, whereby silver is deposited on to glass from a solution
of that metal by deoxidation, in such manner as to cause the silver to adhere
to glass without any previous coating of the latter.
In witness whereof, I, the said Thomas Drayton, have hereunto set my
hand and seal, this Twenty-fourth day of May, in the year of our Lord
One thousand eight hundred and forty-four.