IMPROVEMENTS IN COATING METALS, AND MORE ESPECIALLY IRON AND STEEL, WITH COPPER OR NICKEL, AND IN PRODUCING THEREON CERTAIN IRIDESCENT OR COLORED FILMS
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by Farnham Maxwell Lyte at the Office
of the Commissioners of Patents on the 27th August 1878. A communication
from abroad by Frédéric Weil, of Paris, France.
FARNHAM MAXWELL LYTE, of the Scientific Club, Savile Row, in the County of
Middlesex, Esquire. "IMPROVEMENTS IN COATING METALS, AND MORE ESPECIALLY
IRON AND STEEL, WITH COPPER OR NICKEL, AND IN PRODUCING THEREON CERTAIN
IRIDESCENT OR COLORED FILMS." [A communication from abroad by Frédéric
Weil, of Paris, France.]
This Invention of improvements in coating metals, and more especially iron and
steel, with copper or nickel, and in producing thereon certain iridescent or colored
films, relates, first, to improvements on the Invention for which former Letters
Patent were granted to the said Frédéric Weil and myself, dated September 25th,
1873, No. 3136.
It has been found that the best mode of preparing the metallizing bath, and the
best proportions for the ingredients thereof, are as follows:-35 parts of crystallized
sulphate or an equivalent amount of any other salt of copper are precipitated as
hydrated oxide by means of caustic soda or some other suitable alkaline base. This
oxide of copper is to be added to a solution of 150 parts of Rochelle salt, and
dissolved in 1000 parts of water. To this 60 parts of best caustic soda, containing
about 70 per cent. Na O is to be added, when a clear solution of copper will be
formed. Other alkaline tartrates may be substituted for the Rochelle salt above
mentioned, or even tartaric acid may be employed, but in the case of tartaric acid
or acid tartrates a small additional quantity of caustic alkali must be added,
sufficient to saturate the tartaric acid or acid tartarate. Oxide of copper may also
be employed, precipitated by means of a hypochlorite, but in all cases the pro-
portions between the copper and the tartaric acid should be maintained as above,
and it is advantageous not to increase to any notable extent the proportion of the
caustic soda.
Instead of employing the alkaline battery therein described an ordinary battery
may be employed, or better still a magneto-electric machine. The object to be
coppered is to be cleaned with a scratch brush in an alkalino-organic bath, and

page_text: attached to the cathode, and immersed in the coppering bath, and treated with the
usual precautions, when it will become rapidly coated with an adherent film of
metallic copper.
As the bath gradually loses its copper, oxide of copper as above
prepared should be added to maintain it in a condition of activity, but the quantity
of copper introduced should never exceed that above prescribed as compared with
the quantity of tartaric acid the bath may contain. If the quantity of copper
notably exceeds this proportion certain metallic irisations are produced on the surface
of the object. These effects may be employed for ornamental and artistic purposes.
According to the time of the immersion, the strength of the current, and the pro-
portion of copper to the tartaric acid these iridescences may be produced of different
shades and tints, which may be varied or intermingled by shielding certain parts of
the object by an impermeable coating of paraffin or varnish, while the iridescent
effect is being produced on the parts left exposed. All colors from that of brass to
bronze, scarlet, blue, and green may be. thus produced at will.
If it be desired-to deposit nickel the only modification of the above process
requisite is the substitution of precipitated oxide of nickel for the oxide of copper,
produced by precipitation, as above mentioned..
In the above process it will be observed that the introduction of sulphuric acid
into the bath is avoided, at least except in such insignificant quantities as may still
adhere to the precipitated metallic oxides.