A PROCESS FOR PRODUCING A PATINA, AND AN ARRANGEMENT FOR CARRYING OUT THE PROCESS

Abstract: A process for producing a patina on an object (7) which has a surface coating of copper material. It is possible to obtain the desired degree of patina without the presence of dangerous chemicals. The objects (7) is pre-treated with steam (5) in a chamber (1) containing water (14). After this, the object (7) is exposed to gas (4), preferably from an oil burner (19) until a homogeneous coating of copper oxide (CuO) has formed on the object (7), after which the object (7) is again treated with steam (5) so that a film of liquid is formed on the object (7) which is then dried, whereby monovalent copper oxide (Cu2O) is converted into divalent copper oxide. The invention also relates to an arrangement for carrying out the said process.

Description: A Process for Producing -a Patina, and an Arrangement for carrying out the Process The present invention relates to a process for pro¬ ducing a patina on an object which has a surface coating of copper material. Jntil now it has been impossible to produce artifi- cially the natural patina on an object with a surface coating of copper material, such as copper plate for ex¬ ample, which has been exposed to atmospheric air. Sub¬ stitutes for this patina have always been effected with chemicals of various kinds, and few if any of these "patinas" have been resistant, so that it is always nec¬ essary to protect them with lacquer, etc. The problem has also been to produce a real patina which is more uni¬ form than naturally developed patina, and to produce a patina within a limited period of time. ϊk e natural patina on copper plate consists of two different oxides: On the outside there is a brown to brownish-black di¬ valent copper oxide ( CuO ) which is completely resistant to both relatively weak alkalies and also to acids, and which has a matt surface. Inside this oxide layer there is a thinner layer of monovalent copper oxide (CU2O) which is disposed directly on the metal surface. This oxide is yellow to yellowish-red in colour, and is not resistant to relatively weak acids and alkalies. The main object of the present invention is there¬ fore primarily to provide a process of the kind described above which solves the above-mentioned problems and 1. endows the patina with the same resistance as that of a naturally developed patina, 2. provides a more uniform coating of patina than occurs with natural patina, and 3. produces the patina in a very limited period of time. The said object is achieved with a process accord¬ ing to the present invention which is essentially charac¬ terised in that the object is pre-t eated with steam in a chamber containing water, the object is then exposed to gas, preferably from an oil burner, until a homogene¬ ous coating of copper oxide (CuO) has formed on the ob¬ ject, after which the object is again treated with steam so that a film of liquid is formed on the object which is then dried, whereby onovalent copper oxide (C 2 ϋ) is converted to divalent copper oxide. A further object of the present invention is to pro¬ vide an arrangement which is suitable for carrying out the said process. This further object is achieved with an arrangement according to the present invention which is essentially characterised in that a chamber has a container intended for water, preferably at the bottom of the chamber, and that a ventilation aperture and a heat supply duct equip¬ ped with a filter and leading from an oil burner com uni- cate with the said chamber. The invention is described below by way of a pre¬ ferred embodiment example, with reference to the accom¬ panying drawing on which a chamber which is suitable for use when carrying out the patina-producing process accord- ing to the invention is shown schematically in cross- section. The present process for producing a patina is ex¬ pediently carried out in a chamber 1 shown on the drav/ing and comprising connections 2 and 3 for the supply of gas - and Steam 5 respectively, and a ventilation aperture 6 for evacuating the gas and/or the steam mixture contained in the chamber. Before it is treated in the chamber 1 the relevant object 7 . which has. a surface coating of copper material such as copper plate, for example, which can be used as external cladding on external doors, for example, must OMPI be e allurgically cleaned in order to obtain a perfect result. For this purpose, blasting can be carried out to accomplish the said surface cleaning of the object 7» A further requirement is that the object should be positioned substantially horizontally during its treatment in the chamber 1. A holder S enabling the said require¬ ment to be fulfilled and which can easily transport a plurality of objects 7 into or out of the chamber 1 may be of the kind shown on the drawing, for example. The objects 7 a-r- releasably connected via their respective terminal edges 7 and 73 to spacer devices 9 » preferably in the form of strips, by means of co-acting connecting devices 10, so that they can be mounted on supports 11 on the holder 8, which can be moved on wheels 12. A container 13 which is open at the top and is inten¬ ded for water .1-4- is located in the bottom part of the cham¬ ber for cooling the chamber 1 and the objects 7 contained therein. After the holder 8 with the objects 7 mounted on it has been put in the chamber and the latter has been sealed, steam 5, preferably low-pressure steam, is supplied, for example from a low-pressure steam boiler 15, via a steam supply device 16 through the opening 3 into the inner space 17 in the chamber for a period of three minutes, for ex- ample, to produce condensation on the object 7- The said pre-treat ent of the objects 7 by the supply of steam is expediently controlled by means of a magnetic valve con¬ trol arrangement 18. After this, an oil burner unit 19 equipped with a fil- ter and which is installed normally and is designe'd to be fired with what is known as Grade I domestic oil, is started up. The sulphur-containing gas 4- (SO ). which may also be supplied from any other suitable gas source, is conducted from the burner 19 to the chamber 1 via the pipeline 16A and is introduced via the aperture 2 into the inner space 17 in the chamber. A suirable period for the said gas - H- - treatment of the object 7 in e chamber 1 is approxi¬ mately 1.5 hours, allowing a homogeneous coating of cop¬ per oxide (GuO) to form on the object 7 over its surfaces 70, 7D. Sulphur dioxide (SO- dissolved in the water 1 and forming sulphurous acid (H SO-) with the water is there¬ after evaporated away entirely ventilating the space 17 in the chamber 1, for example by actuating an air- evacuating fan 20 adjoining the aperture 6. After this, a new film of water is deposited on the object 7 by introducing water vapour 5 into the chamber 1 for the length of time necessary to achieve the desired colour and coating thickness on the object 7 . expediently approximately 1 - 4- hours, and preferably 2 - 3 hours. In the next stage the water is evaporated away, by ventilation for example. Monovalent copper oxide (Cu_o) is converted by the above process to divalent copper oxide on the object 7. The object 7 which has thereby obtained the desired degree of patina can thereafter stand up to normal treat ¬ ment, but it cannot be treated again in the above-mentioned way, and for this reason it is important that the process should be carried out with the correct periods of time for the desired degree of patina to be obtained. The invention is not limited to the embodiment ex¬ ample described above, but may be modified within the framework of the following Patent Claims without exceed¬ ing the concept of the invention.

Claims: P a n C l a i m 1. A process for producing a patina on an object (7) which has a surface coating of copper material, characterised in that the object (7) is pre-treated with steam (5) in a chamber (1) containing water (14-), he object (7) is then exposed to gas (4-), preferably from an oil burner (19)• > until a homogeneous coating of copper oxide (CuO) has formed on the object (7), after which the object (7) is again treated with steam (5) so that a film of liquid is formed on the object (7) whic is then dried, whereby monovalent copper oxide (Cu 2 0) is converted to di¬ valent copper oxide. 2. A process according to Patent Claim 1, character¬ ised in that sulphur dioxide (SOp) which has dissolved in the water during the gas treatment and has formed sulphur- ous acid (ϊ^SO- z ) is evaporated away entirely, for example by ventilation (6, 20). 3. A process according to either of the above Patent Claims, characterised in that, after the object (7) has been treated with the gas it is supplied with water vapour (5) for the period of time necessary to achieve the desired colour and coating thickness on the copper material coating the objects, for example, between 1 and 3 hours. 4-. A process according to any of the " preceding Patent Claims, characterised in that the drying is accomplished by ventilation (6, 20). 5. A process according to any of the preceding Patent Claims, characterised in that the object (7) is positioned substantially horizontally in the chamber (1), and that the object (7) is subjected to blasting or some other suitable treatment so that it is metallurgically cleaned before it is steam-treated. C. A process according to any of the preceding Patent Claims, characterised in that the said pre-treatment with steam (5) is carried out with low-pressure steam for an ., appropriate time, for example three minutes. 7- -A. process according to any of the preceding Patent Claims, characterised in that the object (7) is mounted via its respective ends (7A, 73) on spacer devices (9) o means of which, the object (7) is held spaced apart from a surrounding object during treatment in the cha - ber (1). .8. An arrangement for carrying out the process accord¬ ing to any of the preceding Patent Claims, to produce a patina on an object (7) which has a surface coating of copper material, characterised in that a chamber (1) has a container (13) intended for water (14-), preferably at the bottom of the chamber, and that a ventilation aper¬ ture (6) and a heat supply duct (2) equipped with a fil¬ ter and leading from an oil burner, and a steam supply opeiύng (3) espectively communicate with the said chamber (1). 9- An arrangement according to Patent Claim 8, characterised in that spacer devices (9) ? which are pre¬ ferably in the form of strips, can co-act with devices (10) which can be releasably connected to the terminal edges (7A, 73) of the object.

Inventors: BENGTSSON FRED BERNHARD, BENGTSSON, FRED, BERNHARD
Applicants: THERMACORE AB, AB THERMACORE
Application year: 1984
Main classification: C23C8
IPC codes: C23C8