IMPROVEMENTS IN COATING OR COVERING METALS WITH OTHER METALS
Year: 1842

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
HENRY FOX TALBOT, of Lacock Abbey, in the County of Wilts, Esquire, 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 sixth year of Her reign, did,
for Herself, Her heirs and successors, give and grant unto me, the said
William Henry Fox Talbot, Her especial licence, full power, sole privilege
and authority, that I, the said William Henry Fox Talbot, my exors, admors,
and assigns, or such others as I, the said William Henry Fox Talbot, my
exors, adiñors, or assigns, should at any time agree with, and no others,
from time to time and at all times thereafter 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 OR COVERING METALS WITH OTHER METALS;" in which
said Letters Patent is contained a proviso, that I, the said William Henry
Fox Talbot, shall cause a particular description of the nature of my said
Invention, and in what manner the same is to be performed, to be 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
onnear

page_text: NOW KNOW YE, that in compliance with the said proviso, I, the said
William Henry Fox Talbot, do hereby declare that the nature of my said
Invention, and 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 first part of my Invention is a method of preparing the surface of
metallic articles intended to be gilt. This method consists in first covering the
surface of such articles with a thin coating of silver; this is conveniently done
by dipping them into a weak solution of silver in hyposulphite of soda; but
any other of the known methods of silvering may be adopted instead. The
silver coating should be very thin and hardly visible. Even a thinner coating
than this is often found to improve the subsequent gilding.
The second part of my Invention is another method of preparing the surface
of metallic artieles intended to be either gilt or silvered. This method consists
in attaching the article, being first well cleaned, to one of the poles or
electrodes of a voltaic battery, and then plunging both the poles into a vessel
containing a mixture of water with any convenient acid or salt. But it must
be understood that this vessel does not contain either gold or silver, or any
other metal in solution. The battery must be so arranged that decomposi-
tion of the water in the vessel may ensue, and that the article operated on may
give off hydrogen gas during some time. It is then to be quickly detached
from the battery and immediately thrown into another vessel containing a
proper solution of gold or silver, whereby it soon receives a coating of one of
those metals. It is then taken out and washed in a third vessel, containing
pure water.
The same series of operations is then repeated, videlicet, causing
the surface of the metal to give off hydrogen, dipping it quickly into another
vessel containing a solution of gold or silver, and into a third vessel containing
water, whereby the thickness of the coating first obtained is encreased. The
process is then to be repeated as before, and so on, until a sufficient coating
has been obtained.
Note. If the article were attached to the contrary pole of the battery, its
surface might be thereby cleaned, supposing it were tarnished and required
it. But this is very different from my Invention above described, and forms
no part of it.
With respect to this part of my Invention, I claim the preparing the surface
of articles intended to be gilt or silvered, by causing them to give off hydrogen,
being connected with the poles of a voltaic battery as aforesaid.
The third part of my Invention is a method of gilding metallic articles, by
dipping them into a mixed solution containing gold, and one of the baser

page_text: metals. I take the common solution of chloride of gold, or any other con-
venient solution of gold, and mix it with a solution of nitrate of lead, or with a
solution of bydriodate of zinc, or other solution containing one of the baser
metals (such of them as would precipitate, the gold being of course excluded).
I then dip the articles into this mixed solution until they are sufficiently gilt.
I prefer to use the hydriodate of zinc, and I think the best way is to form two
mixtures of different proportions, the first containing very little of the gold, the
second a much larger proportion. The articlo is first to be dipped in the first
or weaker mixture, which serves to prepare its surface for receiving a thicker
coating from the second or stronger mixture. With respect to this part of my
Invention, I claim the employing a mixed solution of gold and one of the baser
metals (with the exception of mercury) for the purpose of gilding metallic
article3.
The fourth part of my Invention consists in using a solution of chloride of
gold, mixed with a solution of boracic acid, for the purpose of gilding articles
of brass or other metal. I find that the addition of this acid produces a more
pleasing color than is produced by the use of the chloride alone. This acid
may also be added to other solutions of the metal instead of using the chloride.
The fifth part of my Invention is as follows:-When metallic articles are
dipped into a solution of gold, which is not altogether suitable to the purpose
of gilding, they often acquire a dark tint, which is not pleasing. In order to
remove this, I dip such articles into a very weak solution of the nitrate of
mercury in water, which soon causes the surface to brighten and acquire more
lustro. The articles may then be again dipped into a solution of gold, and
then again into the weak solution of mercury, and so on; any excess of
mercury may be afterwards removed by an acid, assisted by voltaic action, the
article being properly placed in the circuit of a battery. With respect to
this part of my Invention, I claim the using a solution containing mercury,
for the purpose of improving the appearance or brightening the surface of
articles which have been gilt imperfectly, or of too dark a color, and the
removing the excess of mercury from gilt articles by voltaic action.
The sixth part of my Invention is as follows:-When metallic articles are
dipped into a solution of silver they only receive a coating of limited thickness,
the effect ceasing after a time, and no more silver being deposited, in con-
sequence of the metal on the surface of the article having become similar to that
in the solution. But if made again dissimilar, the effect is, to a certain extent
removed. In order to create such dissimilarity, the article may be dipped into a
different solution of silver, or into a solution of some other metal, only a very
slight coating of which is required, and is most conveniently obtained by the aid

page_text: of a voltaic battery. The article is then replaced in the first solution of silver,
and these dippings are then to be repeated alternately. The like method of
alternate dipping may also be applied to the solutions of gold. The methods of
coating metals, described in the present Specification, are more especially
applicable to the coating of brass, copper, silver, German silver, iron, and steel.
In witness whereof, I, the said William Henry Fox Talbot, have here-
unto set my hand and seal, this Ninth day of May, in the year of our
Lord One thousand eight hundred and forty-three.