A New or Improved Method of Coating Copper or Copper Alloys with Patina.
Year: 1897

page_text: Date of Application, 27th Apr., 1897
Complete Specification Left, 7th Jan., 1898-Accepted, 16th Apr., 1898
Date of Application, 27th Apr., 1097
Complete Specification Left, 7th Jan., 1898-Accepted, 16th Apr., 1898
PROVISIONAL SPECIFICATION.
A New or Improved Method of Coating Copper or Copper Alloys with
Patina.
A communication from ABRAHAM LISMANN, of the Firm Gebrueder Lismann, of
Munich, Kingdom of Bavaria, Empire of Germany.
I, ALFRED JULIUS BOULT, of 111, Hatton Garden, in the County of Middlesex,
Chartered Patent Agent, do hereby declare the nature of this invention to be as
follows:-
This invention relates to the artificial formation of patina upon copper or copper
alloys by electrolysis.
This process is intended to replace the slow natural formation of patina, which
takes place by the oxidation of copper, bronze and the like when exposed to air
and by the action of the carbonic acid contained in the atmosphere, and consists
in quickly and securely forming patina upon copper electrolytically.
This process is especially applicable to the following subjects.
1st. Plates. These are placed in baths and form anodes, the cathodes being also
constituted by plates. The anodes and cathodes are placed at a suitable distance
apart. It is advantageous to combine two plates to be covered with patina into one
anode, by placing them back to back. In this way a greater number of sheets may
be placed in one bath and one side always remains metallic. The electrolyte is
continuously renewed by adding fresh and discharging the used liquid.
2ndly for objects of various shapes, such for instance as copper-sheathing for roofs,
ships, figures cast or made by the electrolytic process etc.
These objects are suspended or placed in a metallic vessel of corresponding shape,
forming the cathode and containing the electrolyte, or the object in question is
surrounded with a cathode of sheet-metal, wire-netting etc. at a suitable distance
and the whole is placed in a vessel containing the electrolyte which also here is
gradually renewed by adding fresh and discharging the old.
3rd for bodies which are already in place, such for instance as roofs, sheathing,
cast pieces such as monuments etc., the cathode is placed as near as possible and
the electrolyte is caused to slowly flow between the anode and cathode, or in case
of monuments, for instance, the cathode is placed at a suitable distance, the whole
is surrounded with a water tight fabric and the electrolyte slowly supplied and
constantly renewed.
The electrolyte consists of a liquid containing carbonates or compounds giving
off carbonic acid under the influence of an electric current. Natural mineral
water makes a good electrolyte, but it must be free from, or contain in very small
quantities, such ingredients as would prevent the formation of metal carbonates
under the action of the electric current. Thus, water containing a minute per-
centage of carbonic acid in the form of lime and magnesia and only a very small
quantity of nitric acid and of sulphate of lime, may be used as the electrolyte. If it
is desired to coat a copper or brass-sheet with patina, said sheet is placed as the
anode in the electrolyte and opposite, at a suitable distance is suspended a copper-

page_text: sheet forming the cathode, and a current of suitable strength is caused to pass
through the apparatus. Then a decomposition of the carbonate of lime and
magnesia and of the water takes place. The oxygen liberated at the anode oxidises
the copper and the carbonic acid which also goes to the anode acts on the metal,
so that gradually a green coating is produced on the surface of the anode. The
electrolyte is constantly renewed during the process by adding fresh and discharging
the old. It rests with the operator to make the coating dark or light, by oxidising
the copper to a greater or lesser extent, as the coating is the darker, the longer
it has been oxidised at the beginning of the process. The object may be covered at
first with a coating of oxide only, and afterwards this oxide may be exposed to the
action of carbonic acid. This oxide can be produced either electrolytically or by
exposure to air or other chemical oxidising substances.
Dated this 27th day of April 1897.
BOULT & WADE,
Agents for the Applicant.
A New or Improved Method of Coating Copper or Copper Alloys with
Patina.
A communication from ABRAHAM LISMANN, of the Firm Gebruder Lismann, of
Munich, Kingdom of Bavaria, Empire of Germany.
I, ALFRED JULIUS BOULT, of 111, Hatton Garden, in the County of Middlesex,
Chartered Patent Agent, do hereby declare the nature of this invention, and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement:-
This invention relates to the artificial formation of patina upon copper or copper
alloys by electrolysis.
This process is intended to replace the slow natural formation of patina, which
takes place by the oxidation of copper, bronze and the like when exposed to air
and by the action of the carbonic acid contained in the atmosphere, and consists
in quickly and securely forming patina upon copper or the like electrolytically.
This process is especially applicable to the following articles, for example:-
1st. Plates. These are placed in electrolytic baths and form anodes, the cathodes
being also constituted by plates. The anodes and cathodes are placed at a suitable
distance apart. It is advantageous to combine two plates to be covered with patina
into one anode, by placing them back to back. In this way a greater number
of sheets may be placed in one bath and one side always remains metallic or clean.
The electrolyte which may be either warm or cold is continuously renewed by
adding fresh and discharging the used liquid.
2nd. For objects of various shapes, such for instance, as copper sheathing for
ships or roofs, figures cast stamped or made by the electrolytic process, or cartridge
cases and the like. In the latter cases the coating of patina serves to protect the
metal from the corrosive action of the gases produced by the explosion. Such
objects as these are suspended or placed in a metallic vessel of corresponding shape,
forming the cathode and containing the electrolyte, or the object in question is
surrounded with a cathode of sheet-metal, wire-netting etc. at a suitable distance
and the whole is placed in a vessel containing the electrolyte which also here is
gradually renewed by adding fresh and discharging the old.
3rd, for bodies which are already in place, such for instance as roofs, sheathing,
cast pieces such as monuments etc., the cathode is placed as near as possible and
the electrolyte is caused to slowly flow between the anode and cathode. In the

page_text: case of monuments, for instance, the cathode may take the form of a mould roughly
corresponding to the shape of the monument, but somewhat larger. This is placed
around the monument and the whole surrounded by a water tight casing or fabric
which is filled with the electrolyte. Preferably the electrolyte is allowed to run
slowly out of the casing and is constantly renewed.
The electrolyte consists of a liquid containing carbonates or compounds giving off
carbonic acid under the influence of an electric current. Natural mineral water
makes a good electrolyte, but it must be free from, or contain only in very small
quantities, such ingredients as would tend to prevent the sufficient formation of
metal carbonates under the action of the electric current. Thus, water containing
a minute percentage of carbonic acid in the form of lime and magnesia and only a
very small quantity of nitric acid and of sulphate of lime, may be used as the
electrolyte. If it is desired to coat a copper or brass sheet with patina, said sheet
is placed as the anode in the electrolyte, and opposite, at a suitable distance is
suspended a copper-sheet forming the cathode, and a current of suitable strength is
caused to pass through the apparatus. Satisfactory results have been obtained by
using a current density of about 01 amperes per one square foot of anode surface.
A decomposition of the carbonate of lime and magnesia and of the water then takes
place. The oxygen liberated at the anode oxidises the copper and the carbonic
acid (carbon dioxide) which also goes to the anode acts on the metal, so that
gradually a green coating is produced on the surface of the anode. The electrolyte
is constantly renewed during the process by adding fresh liquid and discharging the
old. It rests with the operator to make the coating dark or light by oxidising the
copper to a greater or lesser extent, as the coating is the darker the longer it has
been oxidised at the beginning of the process. The object may be covered at first
with a coating of oxide only and afterwards this oxide may be exposed to the action
of carbonic acid. This oxide can be produced either electrolytically or by exposure
to air or other chemical oxidising substances.
Having now particularly described and ascertained the nature of the said inven-
tion, as communicated to me by my foreign correspondent, and in what manner
the same is to be performed, I declare that what I claim is;-
1. The artificial formation of patina upon objects of copper, or alloys thereof
by the action of oxygen and carbon dioxide.
2. The artificial formation of patina upon objects of copper, or alloys thereof by
the action of oxygen and carbon dioxide produced electrolytically.
3. The artificial formation of patina upon objects of copper, or alloys thereof by
the action of oxygen and carbon dioxide produced electrolytically from natural
mineral water.
Dated this 7th day of January 1898.