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METAL COLOR TECHNOLOGY

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Green stain for copper, brass and bronze items

Paint the surface of copper, brass or bronze products in green paint in various ways.

1) The surface of things with a sponge is lubricated first with a strongly diluted solution of copper nitrate with the addition of a small amount of table salt. Then, at what time the item dries out, it is lubricated in exactly the same way with a solution of 1 part potassium oxalate as well as 5 elements of sal ammoniac in 94 parts of weak vinegar. Allow to dry again and again smeared with the main solution; then, after drying, again with a second solution, etc. alternately up until the coloring does not acquire proper strength. Before lubricating the sponge soaked in the solution, it should be squeezed out so that it is moist but not wet. At the end of the painting surface things carefully rubbed with stiff hair brushes, especially in the grooves and crevices. After 8-14 days of labor, brownish-green staining is obtained.

2) Things in several receptions are rubbed with cloth, impregnated with crude oleic acid (product obtained in stearic plants). At first, a dark green layer of copper oleic acid is formed on the surface of things, which, under the influence of oxygen and atmospheric moisture, gradually turns into lighter green carbonate copper. The process is significantly accelerated if oleic acid is sufficiently long enough to insist on copper chips, but after each lubrication with such acid, after the lubricant has dried, things are sprayed slightly (not more than a few drops!) With an aqueous solution of ammonium carbonate.


Brown stain for copper, brass and bronze items

For coloring the surface of copper things in a beautiful and durable reddish-brown color, the following composition can serve: 4 parts by weight of copper acetate (barb), 4 parts of crocus and 1 share of horn trims. Thoroughly crush and mix with such amount of vinegar to form gruel. After smearing the surface of the thing with this composition, it is also allowed to dry out, the thing is heated until the composition turns black; after that, it is also washed off with a polished item - a beautiful reddish-brown color is obtained. If they want the dye to be dark chestnut, then 1 fraction of copper sulfate (in powder) is added to the mixture; for a lighter, yellowish (similar to bronze) staining instead of copper sulfate, Ѕ - 1 fraction of borax is mixed in.

Artistic copper products (statuettes, medals and the like) are best painted with one of the following compositions:

1) 32 elements by weight of copper acetate (barb) in powder, 30 ѕ elements of crushed sal ammoniac and 1 part of strong vinegar to boil with 20 parts of water. After boiling give. stand also carefully drain the clear solution without settling, in which also immerse things for 3 hours.

2) 5 elements of acetic acid copper (crystalline), 7 elements of ammonia, 3 elements of acetic acid and 85 elements of water. A copper thing strongly heated over a charcoal fire should be immersed in a solution. When the thing is painted, remove, wash, dry, and rub with a solution consisting of 1 elements of wax and 4 parts of turpentine.

3) 2 elements by weight of ammonia, 1 share of salt, 1 share of saltpeter,

Boil 1 part of strong ammonia with 96 parts of strong vinegar and immerse things in boiling solution, keeping them there until they are painted properly. After removing, rinse first in a hot solution of ammonia in water, but then in boiling water.

If things are inconvenient to dip into solutions, then they can be greased with a sponge moistened with these solutions; but it is necessary to lubricate evenly, most importantly, quickly, otherwise staining may turn out to be spotty.

It is possible to lubricate things with a liquid gruel made from 2 elements of copper acetate, 2 elements of cinnabar and 5 elements of ammonia with the required number of vinegar. Lubricated things are heated, washed and dried several times, until the coloring does not take the desired shade.

For dyeing in brown paint things from real bronze (i.e., from an alloy of copper and tin) it is better to consume one of the following solutions;

1) 4 elements of ammonia, 1 share of potassium oxalate is also 200 elements of vinegar.

Things smeared with this composition, allow to dry. This operation is repeated until things get the desired color. The rather sharp metallic luster that remains after this quickly disappears, and they also get that pleasant soft brownish color, which under ordinary conditions forms on bronze only after several years (patina).

2) 1 share of crystalline copper acetate, 1 elements of ammonia and 200 elements of water. After smearing the surface of a thing with this composition, it is dried over the fire until the green color disappears. Dilute the above composition with another 340 parts of water and with this diluted solution they smear the thing another 10-15 times, each time drying it over the fire. This diluted composition can be prepared separately: 1 share of copper acetate, 2 elements of salting iron and 600 elements of water. It is even necessary, if you mean to consistently operate on many things. After the first lubrication, the color has an olive-green color, but then it gradually more and more also takes on a pleasant brown shade, which does not disappear even from the very strong heating of things.

Copper, brass and bronze things can also be painted in a very beautiful brown color with a solution of bismuth in strong nitric acid: things after immersing them in this solution are held over the fire until the desired brown color is obtained.


Black stain for copper

Prepare a saturated solution of copper sulphate and add ammonia, until the mixture takes on a bright transparent blue color. The item to be processed is lowered into this solution for a few minutes, then removed and also slightly heated up until it turns black.

There is another means. The copper thing to be blackened is first cleaned with a fine emery paper, after which, up to its cleaned surface, they try not to touch them with their fingers. Then it is either immersed in a liquid solution of platinum chloride, or moistened with it with the aid of a brush. This solution, if it does not own the acid reaction, is slightly acidified with hydrochloric acid.

Very strong blackening of copper products is obtained if you immerse them in a saturated solution of metallic copper in nitric acid and then slightly heat it.


Mordant to imitate patina on copper and bronze products

That beautiful malachite or bluish-green coloration, which is possessed by ancient bronze products, happened under the action of a very long exposure to them or a humid atmosphere or the moist soil in which they were located. Chemical research has shown that the reason for this patina (Patina antica) consists in bringing up a more or less thick layer of copper carbonate on the surface of copper or bronze, i.e. the same copper salt that malachite is made of. This patina is identical with malachite, not only in composition as well as in appearance, but also in the beginning.

In order to artificially obtain a green color very similar to a real patina, it is necessary, if possible, to imitate the process by which the natural formation of a patina is also performed on malachite, i.e. to put things in conditions that cause slow and gradual upbringing of carbon dioxide on their surface.

To do this, things are transferred to a place with a uniform, moderately warm atmosphere, rich in moisture, and carbon dioxide; they leave them here for a longer or shorter time, lubricating their surface with at least a couple or three times daily with a 1-2% solution of acetic acid in water (or vinegar diluted with 4-5 parts of water).

If there are no similar ready-made rooms at hand, then they arrange special chambers of corresponding size with tightly locked doors. For the continued formation of carbon dioxide, one vessel with crushed limestone or chalk is placed on the floor of this chamber, but above this vessel, another smaller vessel is strengthened, from which hydrochloric acid is continuously and uniformly dripping onto chalk or limestone. Wetting diluted solution of acetic acid (see above) small items made by immersing them in the solution, but large - by watering them from above in the form of a minute rainfall or spraying them with a spray bottle. Soak in this way should not less than a couple of times a day. When a green coating on the surface of a thing becomes noticeable, it is possible to dissolve more acetic acid for wetting with water or even replace it with water.

In order to form a proper patina layer, it is necessary to continue the described finish from 2 up to 6 weeks. The more bronze is richer in copper, the more acidic the wetting solution is, the higher the chamber temperature, the faster the process takes place. But the patina is more natural if its formation is slow.

Before starting the operation, the slightest traces of fat (from the fingers, for example) should be removed from things, for which small things are washed with strong lye also try, if possible, to no longer touch them with your hands.


Green mordant for zinc items

Dissolve 50 parts of sodium sulphate (hyposulphite) in 500 parts of boiling water, add 25 elements of sulfuric acid, filter (to separate the precipitated sulfur) and immerse in solution zinc things that are very quickly covered with a light green patina. If you own things in a solution for a longer time, then the light green color turns into dark green. But the best thing for this kind of paint is to pre-coat zinc with copper beforehand and then deal with them as if with copper.


Brown stain for zinc items

Brown zinc is achieved by repeated lubrication with 4 parts of copper acetate (boiling point arthritis) in 11 parts of vinegar. If zinc products are first smeared with a solution consisting of 1 part of copper and 1 elements of ferrous sulfate in 20 parts of water, but then after drying with a solution of 4 elements of copper acetate in 11 parts of vinegar and polished with a crocus after the operation, the surface of things takes a very beautiful dark - bronze color.

After smearing the zinc items several times with a weak aqueous solution of copper chloride or copper dichloride and then heating them also with a brush, the darker the staining becomes, the stronger the solution was used, the more the lubrication was repeated more times. After repeated renewal of the lubricant, the brown color changes to approximately black.

If you add as much ammonium chloride to the copper chloride solution, as needed, so that the sludge that forms first will be dissolved again, then things will turn a reddish color from re-lubrication with such a solution. By adding a little vinegar to this solution, they give a yellow-brown tint to the color.

A very beautiful brown color alienates a solution of 15 elements of chromic alum, also 15 parts of sodium sulfate (hyposulfite) in 500 parts of boiling water, while cooling 25 elements of sulfuric acid are mixed into the solution. Then it is filtered and heated to a boil, but then things are immersed in it and kept in it, stirring it until they take on the desired shade.

Small zinc items can be painted in brown-bronze paint by immersing them in a weak solution of copper sulfate, acidified with vinegar. After immersion, things are dried on the atmosphere and the immersion is repeated (drying each time) until the coloring does not give the desired shade. The weaker the copper solution, the more often the immersion is repeated, and the more beautiful the stronger color.