US2587216A - Process for coating especially metallic articles with an ancient green patina - Google Patents

Description

Patented Feb. 26, 1952 OFFICE PROCESS FOR COATING ESPECIALLY METALLIC ARTICLES WITH AN AN- CIENT GREEN PATINA Mario Quadrio, Como, Italy No Drawing. Application May 19, 1950, Serial No. 163,091. In Italy May 27, 1949 6 Claims. (Cl. 1486.24)

It is an object of the present invention to provide a process whereby it is possible to coat various articles, especially those made of a metallic alloy such as bronze and/or brass, with a malachite green or ancient green patina, which makes them aesthetically and artistically worthy andsought for, avoiding at the same time the inconveniences of the oxidation that would otherwise spoil the external aspect thereof.

The process consists in subjecting the piece to be treated to a first dipping in a solution of potassium sulfide, and then to a second bath in sulfuric acid, whereupon the same is allowed to dry and finally dipped in a third bath of sal-ammoniac, followed by a drying period in the ai and by a repeated dabbing and moistening by means of a flock of cotton or a cloth pad drenched with salammoniac, every moistening being followed by successive drying periods in the air until there are formed at the surface of the article, on the superficial ancient green patina, stains of a malachite green, whereupon the superficial patina thus obtained is fixed with an alcoholic solution of shellac, applied by means of a flock of cotton and, after a drying period finally protected by a film of transparent nitro-cellulose.

Example To coat with a malachite green ancient patina a vase or amphora made of a bronze or brass alloy, the object is taken and dipped in the first bath formed by: 40 grs. of dry potassium sulfide dissolved in 10 liters of water, and kept there for approximately 1 minute. The object removed from this first bath is dipped, while still wet, and maintained for approximately 5 minutes, in a second bath made of: 500 grs. of sulfuric acid at 66 B. diluted in liters of Water.

The piece is then taken out of this second bath and allowed to dry in the air, with or without the aid of dry air drafts to reduce the drying time, whereupon the dry piece is clipped, and maintained for approximately 5 minutes, in a third bath formed by: 1500 grs. of sal-ammoniac dissolved in liters of water.

' Then the object is taken out and is allowed to dry in the air, or in dry air, and when it is perfectly dry it is moistened by means of a flock of cotton or a pad dipped in the solution of the third oath, that is in the sal-ammoniac solution.

This process of moist dabbing and successive drying must be repeated for instance three times,

until on the surface having already acquired an ancient green background there are formed malachite green stains. The green patina thus 9btained must now be fixed by means of a solution of 200 grs. of shellac in 2 liters of 96% alcohol, with the addition of 5 grs. of a malachite green aniline color, if desired. This solution must be applied always by means of a flock of cotton or a cloth pad, or a similar applicator. When the surface is perfectly dry, the same is finally coated with a film of transparent nitrocellulose varnish, preferably applied by means of a spray-gun.

- It should be noted that the successive application of the sal-ammoniac solution, must be made as it has been described above, by means of a fiock of cotton or cloth pad pressed on the surface, place by place, in order to obtain the desired aesthetic aspect, that could not be obtained otherwise, for instance by means of a brush. A

brush application in fact would bring about some strip efiects that would completely spoil the aspect of ancient patina on the object. What has been called dabbing or moistening consists in a wetting operation of the surface applied in an almost perpendicular direction thereto, and not parallel to the same.

The final application of the superficial protective film of nitrocellulose may instead be quickly obtained by means of a spray-gun or also in any desired manner.

The proportions of the ingredients given in the example are not limiting but only indicative, to enable the expert to realize the invention; but it is evident that they may undergo variations within reasonable limits, and it is also possible to add, other inert substances in respect of the reactions forming the object of the invention, without therefore departing from the field of the present invention.

The coatings obtained have a really pleasing aspect and simulate really outstanding and unexpected characteristics of antiquity and valuableness, though being obtained by a quick and simple process.

W hat I claim is:

1. A process for forming an ancient green patina on objects of bronze and bras comprising subjecting the object to be treated to a first dip ping in a solution of potassium sulfide, then to a second bath of sulfuric acid, drying the object and dipping it in a third bath of sal-ammoniac, again drying the object in the air, and then subjecting the object to a repeated moistening on its surface by dabbing it with an applicator wetted in the solution of sal-ammoniac, applied by operating perpendicularly to the surface, following each dabbing regularly with a drying period in the air, until on the surface there are formed,

over the ancient green back-ground, stains of a malachite green shade, then fixing th patina thus obtained with a solution of shellac in alcohol, applied with an applicator, completely drying the surface, and finally, applying a protective film of transparent nitrocellulose.

2. A process according to claim 1 in which the potassium sulfide solution, forming the first bath, is made of approximately four parts by weight of dry potassium sulfide dissolved in 1000 parts of water, and in which the length of time of the dipping in said solution is approximately 1 minute.

3. A process according to claim 1 in which the sulfuric acid bath is prepared approximately with 5 parts by Weight of 66 B. sulfuric acid diluted in 100 parts of water, and the length of time of the dipping in the acid bath is approximately five time that of dipping in the first bath.

4. A process according to claim 1 in which the composition of the third bath of sal-ammoniac is formed by 1.5 parts by weight of solid ammonium chloride dissolved in 20 parts of water, and the length of the time of dipping in the third bath is equal to that in the second bath.

5. A process according to claim 1 in which the liquids for fixing the patina, after the successive moistening and dabbing operations have been performed, are formed of two parts by weight of shellac dissolved in 20 parts by weight of 96% alcohol.

6. A process according 'to claim 1 in which the liquids for fixing the patina, after the successive moistening and dabbing operations have been performed, are formed of two parts by weight of shellac dissolved in 20 parts by weight of 96% alcohol, with a malachite green aniline color.

MARIO QUADRIO.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Freeman Mar. 13, 1934 OTHER REFERENCES Number

Claims (1)

1. A PROCESS FOR FORMING AN ANCIENT GREEN PATINA ON OBJECT OF BRONZE AND BRASS COMPRISING SUBJECTING THE OBJECT TO BE TREATED TO A FIRST DIPPING IN A SOLUTION OF POTASSIUM SULFIDE, THEN TO A SECOND BATH OF SULFURIC ACID, DRYING THE OBJECT AND DIPPING IT IN A THIRD BATH OF SAL-AMMONIAC, AGAIN DRYING THE OBJECT IN THE AIR, AND THEN SUBJECTING THE OBJECT TO A REPEATED MOISTENING ON ITS SURFACE BY DABBING IT WITH AN APPLICATOR WETTED IN THE SOLUTION OF SAL-AMMONIAC, APPLIED BY OPERATING PERPENDICULARLY TO THE SURFACE, FOLLOWING EACH DABBING REGULARLY WITH A DRYING PERIOD IN THE AIR, UNTIL ON THE SURFACE THERE ARE FORMED, OVER THE ANCIENT GREEN BACK-GROUND, STAINS OF A MALACHITE GREEN SHADE, THEN FIXING THE PATINA THUS OBTAINED WITH A SOLUTION OF SHELLAC IN ALCOHOL, APPLIED WITH AN APPLICATOR, COMPLETELY DRYING THE SURFACE, AND FINALLY, APPLYING A PROTECTIVE FILM OF TRANSPARENT NITROCELLULOSE.