IMPROVEMENTS IN COATING, COVERING, OR PLATING CERTAIN METALS
Year: 1840

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, we, GEORGE
RICHARDS ELKINGTON and HENRY ELKINGTON, of Birmingham, in the County of
Warwick, Gentlemen, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Twenty-fifth day of March, in the third year of Her reign,
did, for Herself, Her beirs and successors, give and grant unto us, the said
George Richards Elkington and Henry Elkington, Her especial licence, full
power, sole privilege and authority, that we, the said George Richards
Elkington and Henry Elkington, our exors, adññors, and assigns, or such
others as we, the said George Richards Elkington and Henry Elkington,
our 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, our Invention
of "IMPROVEMENTS IN COATING, COVERING, OR PLATING CERTAIN METALS;" in
which said Letters Patent is contained a proviso that we, the said George
Richards Elkington and Henry Elkington, or one of us, shall cause a
particular description of the nature of our said Invention, and in what
manner the same is to be performed, to be inrolled in Her said Majesty's

page_text: 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, we, the said
George Richards Elkington and Henry Elkington, do hereby declare that
the nature of our 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:-
Our Invention consists of four parts, and has reference to several distinct
operations, processes, or methods, videlicit :-
First, to a method of covering, coating, or plating copper and brass with
silver, by first applying a coating of silver to the surface of the metal to be
plated, and afterwards fusing the same thereon, so as to cause the silver
to unite and alloy with the surface of the coated metal, in the manner hereafter
described.
Secondly, to a method or methods of coating, covering, or plating certain
metals with silver by the use of a solution of silver, and further by the use of
a solution of silver in connection with the application of a galvanic current, as
also herein-after described.
Thirdly, to a method or methods of coating, covering, or plating certain
metals with gold by the use of a certain solution of gold, and further by the
use of a solution of gold in connection with the application of a galvanic
current, as also herein-after described.
Fourthly, to a method of preparing irou so as to render it better fitted for
receiving a coating of copper or other metals.
The first branch of our Invention, videlicit, the method of coating metal
with silver by fusing the coating surface, is thus performed:-The metals to be
plated being first rendered perfectly clean (in the usual manner) are then
to be silvered. This may be done by any of the known modes of silvering in
use for this purpose. But the method which we prefer and adopt is either
that pointed out and described in the Specification of a Patent granted to
Henry Elkington, on the fourth day of December, One thousand eight hundred
and thirty-seven, or that herein-after pointed out in this our Specification as
the process of coating with silver without the use of the galvanic battery.
Upon the surface thus silvered we apply a hot solution of nitrate of silver
more or less concentrated according to the thickness of the coating of silver
required, which we perform by immersing the metal to be coated in the
solution. When this has been effected we submit the metal to a temperature
sufficient to expel all the acid, and leave a merely metallic coating of silver.

page_text: This takes place when the metal is brought to a state a little below red heat,
and may be ascertained by observing when the surface of the metal assumes a
whitish appearance. The article is then ready for the process of fusion, which
we perform in the manner following:-Take a sufficient quantity of calcined
borax and put it into a suitable vessel. The vessel which we use for this
purpose is of cast iron made after the shape of a glass maker's pot and heated
by a surrounding flue. In this vessel the borax is to be fused, the
temperature being raised until the borax becomes quite fluid and of sufficient
heat to melt silver, which may be ascertained by immersing therein a piece
of metal coated with silver. The time required to effect perfect fusion of the
silver will depend partly on the temperature of the molten borax and partly on
the nature of the work to be done; if the articles are of thin wrought metal
fusion will take place in from a few seconds to a minute. Care must,
however, be taken where the heat is sufficient for that purpose, that the
copper be not in part melted, as will sometimes happen if the article be
suffered to remain too long in the flux. On the other hand, if the articles are
massive, as some heavy cast goods, the time necessary to effect perfect fusion
of the silver will be comparatively long, and in these cases care must be taken
that every part of the surface is fused, attention being directed in particular
to the thicker or more solid parts of the article, which, of course, will be
longer in arriving at the necessary degree of heat, and will therefore be the
last to fuse. This the workman will readily ascertain by lifting the work
from time to time out of the borax, for if the silver be fused the borax will
run off from the metal, and the surface will assume the lustre of melted
silver, whereas if it be not perfectly fused the borax will adhere. In
practice we have found it, convenient, when the article to be coated is
large, to attach it to an iron rod or strong wire, so as to enable the
workman to move the article readily during the process of fusion, and this
has the further advantage of causing the silver to flow more equably over the
whole surface; but if the articles are small it will be found convenient to put
a number of them together into a shallow basket made of strong iron wire or
of perforated sheet iron, or, which is still better, of platinum. This may
be lifted into or out of the borax by means of a handle or rod attached, and
when the work is perfectly fused it may be lifted out therefrom with a pair of
light tongs or the like. When the fusion of the silver surface of the article is
complete, we cool it either by immersion in cold water or gradually by
exposure to the air, preferring, however, the former, and afterwards boil it in
dilute sulphuric acid (composed of one part acid to twelve parts of water) until
the adhering borax is all dissolved. This method of plating is of advantage

page_text: where hardness is required, as the process of fusion alloys the silver with the
surface of the copper, and renders it extremely hard. For a finish to improve
the whiteness of the silver surface, the article may be annealed and boiled in
dilute sulphuric acid or muriatic acid, as practised by silversmiths; but we
prefer to apply a slight coating of pure silver by means of a galvanic current,
as herein-after described in this our Specification. Of the metals to be thus
coated we have found copper and its alloys with zinc, such as are known
in commerce by the terms of gilding metal and good brass, to succeed best.
We claim therefore, in respect of this part of our Specification, the method
of coating copper and its alloys with silver, by the process of fusing silver upon
the surface of the coated metal in the manner above described, whereby the
coating of silver is alloyed or united with the surface of the coated metal.
The second branch of our Invention, which consists in the coating, covering,
or plating of certain metals with silver by the use of a solution of silver simply,
and also by the use of a solution of silver in connection with the application of
a galvanic current, we perform as follows:-First, we dissolve oxide of silver
in a solution of prussiate of potash (cyanide of potassium) in the following
proportion or thereabouts, that is to say, to three pounds of prussiate of potash
dissolved in two gallons of water, we add five ounces of silver in the state of
oxide, and agitate or boil the same until dissolved. The prussiate of soda may
be substituted for the prussiate of potash, but the latter is more convenient.
The solution thus prepared is then ready for use. The articles to be coated
being first rendered perfectly free from scale orgrease, (which we effect by the
usual process of cleaning metals,) are then immersed in the solution. If only
a slight covering of silver be required, as in ordinary silvering, we prefer to
use the solution boiling, and such coating is usually obtained in from a few
seconds to a minute. For this degree of coating the application of the
galvanic battery is not required. But, secondly, if a thicker coating of silver
be desired, as in plated wares, we prefer to use the same solution cold,
and obtain a thicker deposit of silver by the application of a galvanic current.
The methods of producing and applying galvanic currents are various. The
most simple with which we are acquainted is contact with a bar of metallic
zinc or other electro-positive metal. A membranous or porous diaphragm
may also be used, in such a manner that the solution of silver shall occupy one
side, and a dissimilar fluid the other; but we have found that the most
efficient and convenient for the purpose above mentioned are some forms
of those used for philosophical purposes, and known by the names of constant
or sustaining batteries. That which we prefer, aud most frequently employ,
consists of two concentric cylinders closed at the bottom, the outer one of

page_text: which is of glazed and the inner one of unglazed and porous earthenware.
The space between them forms a cell, into which is poured a solution of
chloride of sodium or other exciting fluid; into this a cylinder of zinc is
immersed, with a wire of copper soldered to it and made to bend over and dip
into the inner vessel wherein is contained the solution of silver. The articles
to be coated, where they have not already received a first coat of silver, must
be carefully cleaned; they are then to be placed in the solution of-silver
attached to and kept in contact with the wire, and the current being thus
established the deposition takes place. The thickness of the coating of silver
obtained will depend upon the length of time the metal to be coated is
allowed to remain in the solution and in contact with the wire of the battery,
or, where the articles are more than one, with some one which is in immediate
contact with the wire, so as to keep up the galvanic communication. It will
also vary with the force of the galvanic current, or the force being given with
the quantity of work acted upon, and the proportion of silver contained in
the solution. The articles during this process generally assume a crystalline
appearance, something like that of matted silver, which crystallization
increases with the thickness of the silver deposited. If, therefore, we desire
to have a bright surface, the articles are afterwards scratched or brushed
with wire brushes, in the manner well understood; and if a fine, dead, or
matted surface be required, the same may afterwards be obtained by annealing
and boiling in dilute sulphuric or muriatic acid in the mode well understood.
We have found it desirable to add from time to time a fresh supply of oxide
of silver as the solution becomes exhausted by use. And note, that when
used in connection with the galvanic battery, instead of oxide of silver, the
chloride, cyanide, or other insoluble salts of silver (insoluble, that is, in water)
may be employed. We have also sometimes employed a solution of iodide of
silver in hydriodate of potash or soda, and occasionally the nitrate, oxide, or
chloride of silver dissolved in pure ammonia; but these we have not found so
convenient in practice as the solution of silver in prussiate of potash or soda.
And note, further, that other solutions of silver besides those above par-
ticularized may be employed, such as generally the ammoniacal solutions
of silver,or the solutions of chloride of silver in the muriates of potash or soda
But we have found these combinations difficult in practice, aud less successful,
in their results, and do not recommend them. Moreover, when the galvanic
current is to be applied, a similar result may be obtained as follows:-Let the
article or articles to be operated upon receive a first coating of silver,either by
the method above described or any other of the known processes; and
instead of the solution of silver in the prussiate of potash or other salts, as

page_text: above described, take any simple solution of silver in an acid, so as to constitute
what is ordinarily termed a neutral salt; immerse the article or articles in this
solution, applying the galvanic current in the manner above described, and the
deposit and coating will be effected as before, though not, as far as we have
observed, so perfectly.
The above process applies more particularly to the coating of copper and its
alloys, as brass and German silver; iron may also be coated by the same
method after having first gone through the process of cleansing herein-after
described. When so prepared it may be at once operated on with a solution of
silver and a galvanic current, or may be first coated with copper, and the
copper surface be then covered with silver by the means above described.
Zinc and tin may also be silvered by the above processes, and the same
method is applicable to silver and gold and their alloys. What therefore we
claim in respect of this branch of our Invention is, the method of coating the
metals above mentioned with silver, first, by the use of an oxide of silver
dissolved in prussiate of potash or soda or other analagous salt, or in pure
ammonia; secondly, by the use of a solution of silver in a prussiate of potash
or other analagous salt, or in pure aminonia, in connection with the application
of a galvanic current; and, thirdly, by the use of a solution of silver in an
acid, so as to constitute a neutral salt in connection with the like application
of a galvanic current, the article to be operated upon having in this case
previously received a thin coating of silver, preferring for such first coating
the solution of cyanide of silver.
The third branch of our Invention, which consists as has been said in
coating, covering, or plating certain metals with gold by the use of a solution
of gold simply,and also by the use of a solution of gold in connection with the
application of a galvanic current, we perform as follows:-We take oxide of
gold prepared by any of the known methods, or metallic gold in fine division,
and dissolve the same in a solution of prussiate of potash or soda; to about
two ounces of gold converted into oxide we add two pounds of prussiate of
potash dissolved in one gallon of water, and boil the same for half an hour;
the solution is then ready for use. The articles to be gilt or coated being first
cleaned, are to be immersed in the boiling solution of gold, and where aslight
coating only is required the gilding is usually effected in from a few seconds
to one minute; but if we desire to produce a thick coating of gold we prefer to
use the solution in a cold state, being previously prepared by boiling, and
obtain a further deposit, so as to thicken the coating of gold by means of a
galvanic current applied as described in the former part of this our Specifi
cation with reference to the coating metals with silver. We prefer to keep

page_text: the solution as nearly saturated with gold as possible, and for this purpose we
keep a portion of oxide of gold or of metallic gold in the solution undissolved.
In place of the solution of gold before mentioned, we sometimes employ a
solution of the protoxide of gold or purple of Cassius in the muriates of
potash and soda, or other soluble muriates, but not with so good results as
the solution of gold in prussiate of potash or soda herein-before mentioned,
and generally we find that those salts which combine with gold in a low state
of oxidation, and form compound salts having double bases, and which for the
most part are found in that class known by chemists as "haloid salts, as also
those which are capable of dissolving gold in the metallic state, as the
prussiate of potash, are applicable, though with different degrees of excellence
in the result, for the purposes of this branch of our Invention; and we prefer
to employ the solution of oxide of gold in the prussiate of potash as being the
most convenient in practice, the most economical, and producing the best
result. As in the process of silvering so in that of gilding, when the metal
has received a previous thin coating of gold, a simple salt of gold in dilute
solution and in connection with the galvanic current will produce the effect,
though not, so far as we have observed, so well, or perfectly. The metals to
which this branch of our Invention applies are the same as those before enu-
merated as capable of being silvered.
We claim, therefore, in respect of this branch of our Invention, the method
of coating, covering, or plating the metals above mentioned with gold by the
use, first, of an oxide of gold or metallic gold in fine division dissolved in
prussiate of potash or any soluble prussiate, and also by the use of oxide
of gold dissolved in any other analagous salt; and, secondly, by combining the
action of a galvanic current with the use of a solution of gold, as above
described, giving the preference to a solution ofgold in the prussiate of potash,
as above particularly described. And further, with reference to the two last-
mentioned branches of our Invention, we claim the application of a galvanic
current in connection with solutions of gold or silver, as above described, for
the purpose of coating, covering, or plating metals with gold or silver, whether
the articles to be so coated consist wholly of metal, or the metal form merely a
coating or surface to some other substance of which the article generally is
composed.
The fourth branch of our Invention relates to the preparationofiron. In order
efficiently to coat iron with copper and other metals, we have found it necessary
to prepare or cleanse the surface by a process, the effect of which is to make
and keep the iron in an electro-negative state during the period of the action
of the cleaning acid upon it, and the process which we employ for that purpose

page_text: is the following:-We take dilute acid, by preference the sulphuric acid, com-
posed of one part of acid and sixteen parts of water. The iron articles to be
cleaned are immersed into this solution, being previously brought into con-
nection with a wire, to which a piece of zinc is soldered. In from five to
fifteen minutes, more or less, the black scale of oxide will be found to be
loosened and detached from the iron, leaving the surface bright and metallic.
Instead of the wire, a vessel may be used, into which the iron and diluted acid
may be put, with a slip of sheet zinc bending over and dipping into the solu-
tion, and for practical purposes we prefer a wire basket or vessel of brass; but
as the object is to render the iron electro-negative with respect to the zinc, a
wire or vessel of any metal not actively attached by the acid may be used.
When the iron articles are thus prepared, we remove them direct into another
brass vessel containing sulphate of copper in solution, and having that salt in
excess, and also a small proportion of the dilute acid above described. We take
to one pound of sulphate of copper, three pounds of water, and two ounces of
the dilute acid, and we find it necessary occasionally to add further portions of
the acid while the solution is in use. We keep the articles a few seconds in
this vessel, stirring or moving them, and taking care that some part com-
municates with the vessel. By these means they will be found in a few seconds
to be firmly coated with a thin film of copper, and in a proper state to be
placed in contact with a galvanic current, so as to obtain a further deposition
of copper as may be required, which latter process we perform by means of a
galvanic arrangement, like that described in this our Specification for coating
metals with silver. And we would remark that iron so cleansed may be
coated with other metals by galvanic currents, or the iron so cleansed may be
coated by other known means.
We do not claim in respect of this branch of our Invention the use of the
galvanic current for the purpose of depositing copper on surfaces of iron
generally, such process being known; but what we do claim is, an improved
method of coating iron with other metals by the employment of the above
described mode of cleaning the iron as a preparatory process for such coating
In witness whereof, I, the said George Richards Elkington, for myself
and the Henry Elkington, have hereunto set my hand and seal
this Twenty-fifth day of September, in the year of our Lord One
thousand eight hundred and forty.
GEORGE RICHARDS (L.s.) ELKINGTON.

page_text: AND BE IT REMEMBERED, that on the Twenty-fifth day of September,
in the year of our Lord 1840, the aforesaid George Richards Elkington
came before our said Lady the Queen in Her Chancery, and acknowledged
the Specification aforesaid, and all and everything therein contained and
specified, in form above written. And also the Specification aforesaid was
stamped according to the tenor of the Statute made for that purpose.
Inrolled the Twenty-fifth day of September, in the year of our Lord