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TECHNOLOGY OF METAL PAINTS
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Glossary of terms
The surface of copper, brass or bronze products can be painted in green paint in various ways.
1) The surface of things with a sponge is smeared first with a strongly diluted solution of nitric acid copper with the addition of a small number of table salt. Then, at what time the thing will dry out, it is exactly the same way lubricated with a solution of 1 part of potassium oxalate also 5 elements of ammonia in 94 parts of weak vinegar. Again allow to dry out and again lubricate the main solution; then, after drying, again with a second solution, etc. alternately until as long as the coloration does not gain sufficient strength. Before lubricating, the sponge soaked in the solution should be squeezed out so that it is wet, but not wet. At the end of the coloring of the surface, things are carefully ground with hard hair brushes, especially in grooves and crevices. After 8-14 days of labor, a brownish-greenish stain is obtained.
2) Things in several receptions are rubbed with a cloth impregnated with unrefined oleic acid (the product obtained in stearin plants). On the surface of things, a dark green layer of oleic acid copper is formed first, which, under the action of oxygen, also transforms the moisture of the atmosphere into a lighter green carbonic copper. The process is significantly accelerated, if oleic acid is sufficiently long to insist on copper chips, but after each lubrication with such acid, after drying the lubricant, lightly (not more than a few drops!) Spray with an aqueous solution of aqueous ammonium carbonate.
Brown mordant for copper, brass and bronze things
For coloring the surface of copper things in a beautiful and strong reddish-brown color, the following composition can serve: 4 parts by weight of acetic copper (yary-copper coals), 4 parts of crocus, and 1 share of horn scraps. Thoroughly crush also mix with so much vinegar to form a gruel. Lubricating the surface of the thing with this composition and letting it dry, the thing is heated until the composition is completely blackened; after that it is washed off also the thing is polished - a beautiful reddish-brown color is obtained. If they want the paint color to be dark chestnut, then add 1 part of copper sulfate (in powder) to the mixture; for a lighter, yellowish (similar to bronze), staining, instead of copper sulfate, is mixed with S-1 borax.
Artistic copper products (figurines, medals, etc.) are best painted with one of the following compositions:
1) 32 elements by weight of acetic copper (yary-copper) in powder, 30 - elements of crushed molasses and 1 part of strong vinegar boil with 20 parts of water. After boiling give. To settle also carefully to drain without sludge a transparent solution in which also to load things for 3 hours.
2) 5 elements of acetic copper (crystalline), 7 elements of ammonia, 3 elements of acetic acid and 85 elements of water. Strongly heated over the fire of charcoal, a copper thing to immerse in the solution. When the thing is painted, remove, rinse, and dry, also rub with a solution consisting of 1 wax element and 4 parts turpentine.
3) 2 elements by weight of ammonia, 1 share of table salt, 1 share of saltpeter,
1 part of strong liquid ammonia boil with 96 parts of strong vinegar and also in a boiling solution to immerse things, keeping them there until they do not dye properly. After taking out, wash first in a hot solution of ammonia in water, but then in boiling water.
If things are inconvenient to immerse in solutions, they can be lubricated with a sponge moistened with these solutions; but you need to lubricate evenly, most importantly, quickly, in another way the staining can be spotty.
Lubricate things can be like a liquid slurry prepared from 2 elements of acetic copper, 2 elements of cinnabar also 5 elements of ammonia with the right number of vinegar. The lubricated things are heated, washed, and dried several times, until the coloration does not take the necessary shade.
For painting in brown paint things from real bronze (ie, a copper alloy with tin) it is better to consume one of the following solutions;
1) 4 elements of ammonia, 1 share of oxalate potassium also 200 elements of vinegar.
Things are lubricated with this compound, allow to dry. This operation is repeated until the things get the desired color. The remaining sharp metal gloss remaining on the items quickly disappears, and they also receive that pleasant soft brownish color, which, under ordinary conditions, is formed on the bronze only after a few years (patina).
2) 1 share of crystalline acetic acid copper, 1 elements of ammonia and 200 water elements. Lubricating the surface of the thing with this compound, dry it over the fire until until the green color begins to disappear. Dilute the given composition with another 340 parts of water and with such a dilute solution, lubricate the thing 10-15 times more, each time drying it over the fire. This diluted composition can be prepared separately: 1 share of acetic copper, 2 elements of ammonia and 600 elements of water. This is even necessary if it is meant to operate consistently over many things. After the first lubrication, the color has an olive green color, but then it gradually more and more also takes a pleasant brown shade that does not disappear even from 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 later they are immersed in this solution until the desired brown color is obtained.
Black mordant for copper
Prepare a saturated solution of copper sulphate and add ammonia to it until as long as the mash does not take a bright, transparent blue color. The workpiece is dropped into this solution for a few minutes, then it is removed and slightly heated up until it turns black.
There is another means. The copper thing, which is subject to blackening, is first cleaned with a thin emery paper, after which, until it is cleaned, try not to touch your fingers. Then it is either immersed in a liquid solution of chloride platinum, or it is wetted by it with the help of a brush. This solution, if it does not have any acid reaction, is slightly acidified with hydrochloric acid.
Very strong blackening of copper products is obtained if they are immersed in a saturated solution of metallic copper in nitric acid and then slightly heated.
A mordant for simulating patina on copper and bronze products
That beautiful malachite or bluish-green coloration that ancient bronze ware possesses has occurred under the influence of a very long exposure to them or the humid atmosphere or wet soil in which they were. A chemical study has shown that the reason for this patina (Patina antica) is the education on the surface of copper or bronze of a more or less thick layer of carbonic copper, i.e. the same salt of copper, of which malachite is composed. A real patina is identical with malachite in any way not only in composition, but also in appearance.
To artificially obtain a green coloration, very similar to a real patina, it is necessary, if possible, to imitate the process by which the natural formation of patina is also effected, malachite, i.e. put things in conditions that cause a slow gradual education on their surface of carbonic copper.
For this, things are transferred to a place with a uniform, moderately warm atmosphere, rich in moisture, also with carbon dioxide; leave them here more or less long time, lubricating their surface no less than a couple or three times daily with a 1-2% solution of acetic acid in water (or vinegar diluted 4-5 parts of water).
If there are no such ready-made premises at hand, then they arrange special chambers of the appropriate size also with tightly closing doors. For the unchanged formation of carbon dioxide on the floor of such a chamber, put one vessel with crushed limestone or chalk, but above, above this vessel, another smaller vessel is strengthened, from which hydrochloric acid drips continuously or evenly into limestone or limestone. Wetting with a diluted solution of acetic acid (see above) of small things is done by immersing them in a solution, but large ones - by pouring them from above in the form of a shallow shower or spraying them with a spray gun. Soak in this way should not be less than a couple of times a day. When the green coating on the surface of the thing becomes already noticeable, the acetic acid solution for wetting can be diluted more with water or even replaced with water.
To form the proper patina layer, it is necessary to continue the described finish from 2 to 6 weeks. The more bronze is richer with copper than the acid solution for wetting, the higher the temperature of the chamber, the sooner the process takes place. But the patina is more natural if its formation is slow.
Before the beginning of the operation with things, the slightest traces of fat (from fingers, for example) must be removed, for which small things are washed with a strong liquor, and try, if possible, no longer to touch them with hands.
Green mordant for zinc things
50 parts sodium sulfate (hyposulfite) dissolve in 500 parts of boiling water, add 25 elements of sulfuric acid, filter (to separate the settled sulfur) and immerse in the solution zinc things that are very quickly covered with a light green bloom. If you own things in the solution for a longer time, then the light green color turns into dark green. But it is best for this kind of painting to cover zinc things in advance with copper and then to treat them as if with copper ones.
Brown mordant for zinc things
Brown staining of zinc is achieved by repeated lubrication with 4 parts of acetic copper (yary-copper coals) in 11 parts of vinegar. If zinc products are first coated with a solution consisting of 1 part of copper, 1 element of ferrous sulfate in 20 parts of water, but then dried with a solution of 4 elements of acetic acid copper in 11 parts of vinegar, and after the operation is polished with crocus, the surface of things takes a very beautiful dark -Bronze color.
Lubricating the zinc materials several times with a weak aqueous solution of chloride or cuprous copper and then heating them also by wiping them with a brush, they get a darker coloration the harder the solution is used, and the more times the lubrication is repeated. After repeated renewal of lubrication, the brown color turns into approximately black.
If you add as much ammonia to a solution of cupric chloride as it is necessary for the sludge formed first to dissolve again, then after repeated lubrication with such a solution, the objects are painted copper-red. Adding to this solution a little vinegar, give the color a yellow-brown tinge.
Very beautiful brown coloring alienates a solution of 15 elements of chrome alum and 15 parts of sodium hypochlorite (hyposulfite) in 500 parts of boiling water, 25 elements of sulfuric acid are added to the solution after cooling. Then it is filtered and heated to a boil, but then immersed in it things and keep them in it, stirring until they do not take the desired shade.
Fine zinc things can be painted in a brown-bronze paint by immersing them in a thin solution of copper sulfate, acidified with vinegar. After dipping, the objects are dried in the atmosphere and the immersion is repeated (drying each time) until the coloration does not give the desired shade. The weaker the copper solution, the more often it is necessary to repeat the immersion, the more beautiful the coloration is also the more beautiful.