Patination of copper, as well as other methods of its decorative processing(including at home) make it possible to make products made from this metal more attractive and give them a touch of noble antiquity. Items made not only of copper, but also of its alloys such as can be subjected to such treatment.

Patination and oxidation

The surface of many metals (and copper is one of them), when interacting with the surrounding air and various chemicals, begins to become covered with a thin layer of oxides and oxides. This process, which also leads to a change in the color of the metal surface, is called oxidation. For the most part, the process of metal oxidation occurs naturally, but people have learned to cause it artificially, in industrial or home conditions, which is done to give the product an aged look.

Oxidation should not be confused with patination, a process the essence of which is that on the surface of the metal, when interacting with various chemical elements, a thin layer sulfur or chloride compounds. Patination, which, like oxidation, is accompanied by a change, can also be performed artificially using special compounds.

Copper aging occurs naturally over time or immediately when the surface is treated with any preparations.

If under natural conditions the process of oxidation and patination of copper or bronze can take years, then when special solutions are used, patination occurs in a very short period of time. The surface of a product placed in such a solution literally changes its color before our eyes, acquiring a touch of noble antiquity. Using various chemical compositions, you can perform such procedures as blackening of copper, patination of objects made of copper and bronze, and blackening of brass in production and even at home.

Preparation for processing

Having decided to perform patination or oxidation, you should not only carefully study the question of how to age brass, bronze or blacken copper, but also provide the necessary safety measures. Supermajority chemical compositions which are used to carry out such procedures are very toxic and emit fumes that pose a significant danger to human health. Therefore, to store such substances both in industrial and at home conditions, you should use vessels with well-ground stoppers, which will prevent toxic vapors from entering the surrounding air.

The procedure itself, carried out to change the color of the surface of a product under the influence of chemicals on it, should be performed in a special cabinet to which exhaust ventilation is connected. It should be borne in mind that the doors of such a cabinet should be slightly open during the process of oxidation or patination, which will ensure effective extraction of harmful vapors from its interior.

Products made of copper, brass and bronze should be thoroughly cleaned, degreased and washed before patination. warm water. After the patination or oxidation procedure itself, the treated objects are also washed and placed in sawdust to dry. Using sawdust is a more gentle drying method, since performing such a procedure with a fabric material can damage the thin film of the formed patina, which has not yet been fixed with varnish. In addition, using fabric after patination, it is almost impossible to efficiently remove moisture from the recesses on relief surfaces, and sawdust can easily be pulled out.

Changes in color of copper and its alloys from gray to black

Grey, dark gray or black and its alloys make the appearance of the product more attractive and presentable. To obtain these colors, the degree of saturation of which can be adjusted, you need the “liver of sulfur” composition that has been used for decades. It got its name due to the fact that during the cooking process it must sinter, that is, turn into a caked mass.

To make such a composition for patination at home, you must follow these steps:

• one part of powdered sulfur is mixed with two parts of potash;
• the resulting mixture is placed in a tin can, which must then be put on fire;
• After waiting for the powder to melt and begin to sinter, it is necessary to maintain this process for 15 minutes.

During the sintering process of the powder, a blue-green flame may flare up on its surface, which does not need to be knocked down, since it will not deteriorate the quality characteristics of the sulfur liver. After sintering is completed and completely cooled, the resulting mass should be crushed to a powder state. This powder, if placed in glass jar With a tight-fitting lid, it can be stored for a long time.

In order to patina various metal alloys using liver sulfur, several basic methods are used.

Method No. 1

This method involves the use of an aqueous solution of liver sulfur. It can be used to change the color of products made from the following materials:

• copper;
• sterling silver;
• bronze and brass.

Colors that can be used to paint the surfaces of products using this method, also differ:

• copper and silver - purple, blue (very difficult to obtain), gray, brown-gray, black;
• brass and bronze – soft golden.

If you did not know before how to age copper and form a durable patina film on the surface of this metal, distinguished by a rich black color, use this method. To implement it, a copper product is placed in a solution consisting of a liter of water and 1–20 grams of liver sulfur powder.

To color copper light gray, the solution is prepared according to a different recipe: 2-3 grams of sodium chloride and liver sulfur are dissolved in 1 liter of water. A copper product is placed in the resulting solution, the color change of which should be carefully monitored. After the color of the metal acquires the desired tone, the object to be patinated must be washed with water and dried in sawdust.

Method No. 2

To patina copper, you can also use a solution prepared according to the following recipe: ammonia is added to a saturated aqueous solution of copper sulfate and this is done until the liquid becomes transparent and bright blue. The cleaned and degreased product to be processed is placed in such a solution for several minutes, after which it is removed and subjected to slight heating. After such manipulations, the copper should acquire a rich black color.

Method No. 3

To use this method, which also allows you to qualitatively blacken copper even at home, the object being processed must be cleaned with fine sandpaper. Do not touch the cleaned surface with your hands to prevent grease stains from forming on it. After preliminary preparation Before patination, the object is treated with a solution of platinum chloride or completely immersed in it. In such a solution, if it does not cause an acidic reaction, you can add large number hydrochloric acid.

Method No. 4

A durable oxide film, distinguished by a rich black color, can be formed on the surface of a copper product by immersing it in a composition prepared from nitric acid and copper metal. To make the color change of the copper part more intense, this solution can be further heated.

Getting a patina of other colors

To form an oxide film of a different color on copper, you can even use one of the following methods at home.

Red-brown

To obtain a red-brown oxide film, the copper product is placed for several minutes in a composition prepared from one part of copper sulfate, one part of zinc chloride and two parts of water.

Range from light brown to black

To obtain such a patina, a copper object must be placed in a solution consisting of one liter of water and 20 grams of ammonium sulfide. By changing the heating temperature of the processed product before patination, you can adjust the intensity of coloring.

Light brown

To give the surface of a copper product a light brown color, it is necessary to treat it with a mixture of sodium chromium (124 g/liter), nitric (15.5 g/liter) and hydrochloric (4.65 g/liter) acids, 18% ammonium sulfide ( 3–5 g/liter). This solution is applied with a brush and left for four to five hours.

The easiest way to blacken copper is with ammonia vapor (ammonia). A thicker color is obtained if the product (the wire is pre-soaked in a solution of table salt for several hours).

A review of the Internet showed. that this is not the only method. I found the most information on the forum of ship modellers: http://shipmodeling.ru/

There are actually several ways to achieve that gorgeous brown patina on your brass or brass. You can use chemicals or more environmentally friendly methods. Some chemicals may be caustic and should be used with caution. Then, of course, there are the more common chemicals such as Liver Sulfur, Black Max, and antique solutions containing ferrous nitrate. This is an environmentally friendly method of oxidizing copper and silver. The process takes four to six hours.

Using Homemade Ammonia on Copper and Brass

A small, shallow dish on which to place your metal or jewelry. The container or bag should be large enough to hold a small dish plus hard-boiled eggs with room for storage. Two or three hard-boiled eggs. . Place your jewelry or metal pieces on a small dish. The egg should not touch metal or jewelry. You'll be tempted to look, but don't! Using household ammonia vapor to oxidize metal is actually quite simple and is an inexpensive way to oxidize copper and copper.

The scale of copper products and the desire to obtain a good and durable effect bring us closer to ship modellers. I chose those recipes that forum participants give as proven in practice and for which, in principle, you can find materials:
1. Buy special compounds for blackening (bluing) metal at a jeweler's store or at a hunter's store. (Not cheap!)
2. Prepare black mordant for copper: Dissolve copper sulfate in warm water. The solution needs to be saturated, i.e. add vitriol until it still dissolves. Add ammonia until the mixture acquires a bright transparent blue color. The product to be treated must be immersed in the solution for several minutes, removed and heated until the part turns black.
3. Spread with sulfur ointment and put in a warm place (on the radiator) for several hours. However, they say that the coating is not very stable.
4. Prepare a simplified version of the liver sulfur solution, in which potash is replaced with soda ash. Here's more of the process: " A ceramic bowl with a handle, like a pot. Dissolve two tablespoons in 150 ml of distilled water soda ash(bought at a household chemicals store in a package similar to washing powder) brought it to a boil and began to add colloidal sulfur (bought at a flower fertilizer store), also two or three spoons. The yellow solution began to darken and after 7-8 minutes it turned brown. Either I didn’t calculate the grams in the spoon, or the water boiled away, but the required liquid in my opinion turned out to be not enough and I added more water by eye and boiled it some more. The final liquid turned out to be slightly yellowish-greenish in color. There is a thick layer of yellowish sediment at the bottom. Carefully drained the resulting liquid.
My guns are made of lead covered with copper. Store-bought products did not provide a lasting coating, and this cloudy liquid gave my copper products a radical black color within 1 minute. The coloring is stable, unlike my store-bought ready-made reagents, and uniform. Can be polished with a brush, but becomes dark dark gray and begins to shine."
5. And finally, one more recipe (although there is only a link on the forum, no one has used it): Dissolve 4 g of caustic soda (caustic soda) and 4 g of milk sugar in 100 g of water, boil for 15 minutes, then, with constant stirring, add 4 g of a saturated solution of copper sulfate in small doses. Well-cleaned copper products are immersed in the hot mixture. Depending on the duration of action they will acquire different colors- from golden, green to complete black.
Milk sugar is a baby food product. Here is a link to the manufacturer (distributors include addresses of stores in Russia). http://oltri.ru/page102.html
6. And this is just a recipe from the Internet: Very durable blackening copper products obtained by immersing them in a saturated solution of copper metal in nitric acid and then heating them slightly.

All you need is a clean whipped cream bath, a lid, and a piece of wire or fishing line to suspend your piece and clear out the ammonia. It's a little smelly, but if you're quick, the smell shouldn't be a problem. Under no circumstances should metal or finished jewelry come into physical contact with the ammonia liquid; it is the vapors that will produce this patina. First, clean your piece of brass or copper with alcohol or acetone to remove any oils or dirt so that the patina is uniform throughout the piece.

Do not touch the surface you want to patina. Pour about one inch of ammonia into a pint or quart glass jar. You can use wire or fishing line to hang metal or jewelry just below the mouth of the jar. The piece should not come into contact with liquid ammonia. Screw the lid on and wait a couple of hours. You can check this piece to see what color you want to stop.

05.09.2009

Oxidation and patination of copper, brass and bronze.

Some chemical reactions lead to the formation of oxides and oxides, i.e., oxygen compounds, on the surface of metals. This process is called oxidation.

Often chemical elements, interacting with a metal or alloy, contribute to the appearance of sulfur or chloride compounds. The process of forming such compounds is called patination.

If you dip a metal product into the prepared solution, it literally changes color before your eyes. A sparkling metal product takes on the appearance of an antique product in a few seconds.

Most chemical compounds that are used for patination and oxidation of metals are toxic and dangerous to humans. Therefore, they need to be stored in vessels with ground-in stoppers, and all work involving the release of toxic and flammable vapors and gases should be carried out in a fume hood. The cabinet doors should be slightly open.

Before changing the color of the metal, it is necessary to carry out some preparatory operations. The item is cleaned and degreased, washed well and dried in sawdust. Metal art products and coins should never be wiped with a towel. A towel wipes off fragile patina films that are not secured with varnish; moisture remains in the deep reliefs; the fabric gets caught on high protrusions and can bend them. Sawdust quickly and evenly draws water away from the metal surface.

Patina from gray to black

Preparation of sulfur liver:
To prepare sulfur liver, you need to mix one part of powdered sulfur with two parts of potash in a tin can and put on fire. After a few minutes, the powder will melt, darken and begin to sinter, gradually acquiring a dark brown color. (By the way, the sintering of the patination mass gave the name “liver” in the old days - from the words “oven”, “sinter”.)
During sintering, sulfur vapor may ignite with a weak blue-green flame. Do not knock down the flame - it will not deteriorate the quality of the sulfur liver. After about 15 minutes, stop sintering. For long-term storage, crush the sulfur liver into powder and place it in a glass jar with a tight lid.

Method No. 1
Applies to:
Copper, sterling silver, and bronze or brass (light shade). Does not work on nickel silver.
Colors:
On copper and silver there is a range of shades from purple/blue (difficult to obtain) to brown-gray, gray, black. On brass and bronze - only soft golden.

A durable and beautiful patina forms on the surface of copper treated in an aqueous solution of liver sulfur.

When making a solution in 1 liter of water, add 10-20 g of liver sulfur powder. The patina obtained on metal with a solution of sulfur liver is durable and beautiful, deep black in color. But such intense coloring is not always necessary. Sometimes, to give an antique look to a copper product, it is enough to apply a light gray patina. Pour 2-3 g of table salt and 2-3 g of sulfur liver into a liter of water. Dip a copper plate into the solution. After the required gray color appears, rinse the plate with clean water and dry.

Method No. 2
To blacken a copper item, prepare a saturated solution of copper sulfate, add ammonia to it until the mixture takes on a bright transparent blue color. The copper item being processed is dipped into this solution for a few minutes, then removed and slightly heated until it turns black.

Method No. 3
A copper item to be blackened is first cleaned with a fine sandpaper, after which they try not to touch its cleaned surface with their fingers. She then either plunges into liquid solution platinum chloride, or moistened with it using a brush. This solution, if it does not have an acidic reaction, is slightly acidified with hydrochloric acid.

Method No. 4
A very durable blackening of copper products is obtained by immersing them in a saturated solution of copper metal in nitric acid and then heating it slightly.

Patina red-brown

An aqueous solution of zinc chloride and copper sulfate colors copper red-brown. Mix one part copper sulfate with one part zinc chloride and dilute in two parts water. A few minutes are enough for the copper to acquire a red-brown color. After washing and drying, wipe the metal surface with oil.

Patina from light brown to black

Blackening of the metal is observed when copper is patinated with ammonium sulfide.
20 g of ammonium sulfide is diluted in a liter of water. The product is dipped into the resulting solution or poured on top and wiped with a brush. The work is carried out in a fume hood. Sulfur ions present in an aqueous solution of ammonium sulfide interact with copper ions. Black copper sulfide is formed.
The intensity of the patina on the metal can be of different shades, from light brown to black. The color is adjusted by changing the heating temperature of the plate before patination.

Patina light brown

Gram per liter:
sodium dichromate - 124
nitric acid (density 1.40 gcm3) - 15.5
hydrochloric acid (1.192) - 4.65
Ammonium sulfide 18% solution - 3-5
Apply with a brush immediately after preparation, rinse off after 4-5 hours and repeat after drying 2 times, polish with a dry cloth.

Dark brown to warm black patina

Gram per liter:
ammonium persulfate - 9.35
caustic soda - 50.0
for 5-25 minutes in a bath with a solution heated to 90 -95 degrees. rinse, dry, repeat 2-3 times

Olive to brown patina

Gram per liter:
Berthollet salt - 50*70
copper nitrate - 40*50
Ammonium chloride - 80*100
for 10-15 minutes in a bath with a heated solution to 60-70 degrees.
the resulting films have mechanical strength and corrosion resistance

Patina brown-black

Gram per liter:
Ammonium molybdate - 10
ammonia 25% aqueous solution - 7
the solution should be heated to 60 - 70 degrees

Golden patina

Using more traditional chemicals - safety first!

The ammonia smell on your piece should dissipate quickly, but if you want, you can leave the piece for a while before very carefully buffing any high spots for contrast. Of course, you can use the tried and tested, eco-friendly method of adding a patina to your metal using chemicals such as Liver Sulfur, Black Max and Antique Patina. Some chemicals can be caustic and must be handled with care, both during the patination process and when removing the chemicals afterwards.

Gram per liter:
copper sulfide - 0.6
caustic soda - 180
milk sugar - 180

a solution of alkali and lactose is prepared separately and only then poured together, boiled for 15 minutes and copper sulfide added.
place the product in a heated to 90 gr. solution for 15 minutes.

Patina golden brown with crimson tarnish and moderate shine

Remove your work surface and fold the paper because accidents happen. There is always a cup or bowl with clean water at the ready, as well as a bowl with a small amount of baking soda. Paper towels, old T-shirts, or clean rags are ready for spills and will dry your pieces after you rinse off the chemical you're using. Use safety glasses. Yes, no one likes to wear them, but are you willing to compromise your vision for an accidental splash? Have plenty of water. Make sure you have a well-ventilated area to work in. . Keep these things on hand when you are "patinaing" the metal.

After cleaning copper coins, you can create an artificial patina on them by placing 50 g of copper sulfate and 5 g of potassium permanganate per 1 liter of water in a solution, heating it to a temperature of 70-80C and holding it there until the desired color is obtained.

Green patina

The surface of copper, brass or bronze products can be painted green in various ways.

These are sponge pads that contain permanently attached micro-abrasives. They are used to highlight highlighted areas of your patinated figures.

• Cotton swabs, cotton balls or cotton swabs.
• Brass brush.
• Stainless steel brush.
• You can find them at any grocery store.
• This is my favorite liver shape because it is so versatile.

Are you looking for a way to add a little more dimension to your handmade jewelry? Eat more options decoration finishes than just matte, shiny or matte.

Method No. 1
Using a sponge, the surface of things is first lubricated with a highly diluted solution of copper nitrate with the addition of a small amount of table salt. Then, when the item dries, it is lubricated in exactly the same way with a solution of 1 part potassium oxalate and 5 parts ammonia in 94 parts weak vinegar. Let it dry again and again lubricate with the first solution; then, after drying, again with a second solution, etc. alternately until the coloring acquires the proper strength.
Before lubricating, the sponge soaked in the solution should be squeezed out firmly so that it is damp, but not wet. After painting the surface, rub the items thoroughly with hard hair brushes, especially in the recesses and crevices. After 8-14 days of work, a brownish-greenish color is obtained.

Beyond the world of simple silver and gold lies an incredible landscape of color, ready for you to experiment with: patina! Let's take a closer look at how copper patinas. First of all, you want to cook your pieces so they are free of dirt and oil for best results. This means no fingerprints, no oil. If you have access to a brine pan, now is the time to the right time for use it. If you're not worried, take Britt tape and gently scratch the surface.

Note that this will give your piece more of a satin finish, but make sure the patina has plenty of room to cling. Once it's clean, handle around the edges so you don't transfer any oils onto it. If you've ever done any studio work with copper, you may have noticed that when you heat it up, your metal will begin to change. When copper is heated, some really beautiful colors can be extracted from the metal. reds, purples and blues are all common.

Method No. 2
Things are rubbed in several stages with cloth soaked in crude oleic acid (a product obtained in stearin factories). On the surface of things, a dark green layer of copper oleic acid is first formed, which, under the influence of oxygen and air moisture, gradually turns into lighter green copper carbonate.
The process is significantly accelerated if oleic acid is first infused on copper shavings for quite a long time, and after each lubrication with such acid, after the lubricant has dried, the items are lightly sprayed (no more than a few drops!) with an aqueous solution of ammonium carbonate.

The key is to try to stop before you go too far. Try not to be too attached to a certain color until you get it because it can be frustrating sometimes. Pull the torch out slowly and you won't get huge color hits. bright until it started to cool. The best thing to do here is to experiment and see what you like and what you can stick with. When you find that a sealant is recommended.

Acrylic transparent coatings, beeswax or renaissance wax can help protect your surface and color. The ingredients for this patina are easy to find in your kitchen cabinets. Vinegar and salt, about 3 tablespoons each. Stir until the salt dissolves in the vinegar.

In my previous post #378, where liver sulfur is used for patination/oxidation, there is one point: despite the fact that copper darkens quickly and intensely during processing, there is a suspicion (my knowledge of chemistry is not deep enough to make a 100% judgment) that the composition of the dark coating is only partly contains copper oxide (and does it contain it at all?!), and perhaps most of the component belongs to CuS, because the reagent contains sulfur. I don’t presume to judge on this matter and would be glad to hear the opinion of an experienced chemist (awww). Accordingly, the selectivity of this coating created by the sulfur liver is questionable and awaits its inquisitive researcher. By the way, it’s easy to make sulfur liver at home: sulfur and ordinary baking soda are sintered over low heat, there’s a ton of information about this on the internet, searchers will find it.
And for all those who are suffering and have patiently read this topic up to this point, I want to share (however, apparently there are almost no fans of this issue left) the latest personal discoveries that make obtaining an oxide film on copper very simple and safe, as well as a way to quickly, easily and safely completely remove this film, returning the copper to its original pinkish tint.
1) similar to the industrial method of blackening copper with caustic soda NaOH+NaClO2 with all the risks of working with this caustic compound, and even heated (powerful evaporation is guaranteed), it was decided to try ordinary baking soda and nothing more!.. And lo and behold - everything worked out! What is the essence of the idea: in industry it is profitable to use NaOH, as a widespread, very active and inexpensive reagent, but the use of an alkali such as baking soda will cost many times more and such nonsense can only come to the mind of a household maniac-innovator; NaOH also allows the process to be carried out sufficiently quickly, 15-30 minutes, and in industry time is money. That is why no references to blackening copper with baking soda were found on the Internet (how many of these enthusiasts want to blacken copper at home using improvised methods to obtain selective oxides! Oh madmen!) But! At home, splurging on baking soda is more convenient and safer.
And the next one important point: unlike caustic soda, the process in soda proceeds very slowly (another reason why this topic is unknown - you put copper in soda and almost nothing happens, even after a couple of hours, it seems that it does not work) but is this a problem? Personally, I was in no hurry! In general, 2 teaspoons of soda per about 100g of water gives a saturated solution, into which we place the copper item and leave... After a day we arrive and see a noticeable darkening to a brown-brown hue (as expected), and after the second day the copper item becomes almost black with a slight purple tint! I didn’t keep it for the third day; the photo shows exactly 2 days of exposure. Everything is as it should be! And let someone say that this is not an oxide! Apart from alkali (as well as with caustic soda), nothing was used; the color sequence of darkening completely repeats the description of oxidation using an industrial method: pure copper - brown tint - brown - black - black with violet. In addition to simplicity, accessibility and safety, this household method of oxidizing copper with baking soda has a very interesting and important advantage over the industrial method of blackening with caustic soda: the formation of an oxide film in a soda solution is very slow, which means it is very easy to obtain the desired color intensity and uniformity of film application! Overexpose or overheat/underheat the solution, do not maintain the proportions as in industry - you have to be a complete idiot, the shade scale is plus or minus 1-2 hours of exposure. It is enough to stir the solution (mix, shake) 3-4 times a day to achieve a uniform color of the entire surface. I ended up with a very beautiful piece, uniformly painted black with a purple tint.
2) the discovery of N2 is even worse (of course for smart people this is not a discovery, but nothing like this was found on the internet) and was done “at random” or “what if”, in general, to destroy the film on copper turning it into pure pink copper even faster and easier, using the same baking soda ( teaspoon) + table salt (teaspoon), approximately 100g of water: place copper in this mixture, stir and after a few seconds the copper is as good as new!
I am posting a photo of a copper tube oxidized for 2 days in a saturated soda solution and a washed tube in a soda + salt mixture.
If these ideas help someone make an effective solar collector not much inferior to industrial analogues, save a lot of money and halve the bills to Gazprom for heating or heating, which means I didn’t run in vain on this branch..
I hope these questions are still of interest to someone else.

In my previous post #378, where liver sulfur is used for patination/oxidation, there is one point: despite the fact that copper darkens quickly and intensely during processing, there is a suspicion (my knowledge of chemistry is not deep enough to make a 100% judgment) that the composition of the dark coating is only partly contains copper oxide (and does it contain it at all?!), and perhaps most of the component belongs to CuS, because the reagent contains sulfur. I don’t presume to judge on this matter and would be glad to hear the opinion of an experienced chemist (awww). Accordingly, the selectivity of this coating created by the sulfur liver is questionable and awaits its inquisitive researcher. By the way, it’s easy to make sulfur liver at home: sulfur and ordinary baking soda are sintered over low heat, there’s a ton of information about this on the internet, searchers will find it.
And for all those who are suffering and have patiently read this topic up to this point, I want to share (however, apparently there are almost no fans of this issue left) the latest personal discoveries that make obtaining an oxide film on copper very simple and safe, as well as a way to quickly, easily and safely completely remove this film, returning the copper to its original pinkish tint.
1) similar to the industrial method of blackening copper with caustic soda NaOH+NaClO2 with all the risks of working with this caustic compound, and even heated (powerful evaporation is guaranteed), it was decided to try ordinary baking soda and nothing more!.. And lo and behold - everything worked out! What is the essence of the idea: in industry it is profitable to use NaOH, as a widespread, very active and inexpensive reagent, but the use of an alkali such as baking soda will cost many times more and such nonsense can only come to the mind of a household maniac-innovator; NaOH also allows the process to be carried out sufficiently quickly, 15-30 minutes, and in industry time is money. That is why no references to blackening copper with baking soda were found on the Internet (how many of these enthusiasts want to blacken copper at home using improvised methods to obtain selective oxides! Oh madmen!) But! At home, splurging on baking soda is more convenient and safer.
And the next important point: unlike caustic soda, the process in soda proceeds very slowly (another reason why this topic is unknown - you put copper in soda and almost nothing happens, even after a couple of hours, it seems that it doesn’t work) but is this a problem? ? Personally, I was in no hurry! In general, 2 teaspoons of soda per about 100g of water gives a saturated solution, into which we place the copper item and leave... After a day we arrive and see a noticeable darkening to a brown-brown hue (as expected), and after the second day the copper item becomes almost black with a slight purple tint! I didn’t keep it for the third day; the photo shows exactly 2 days of exposure. Everything is as it should be! And let someone say that this is not an oxide! Apart from alkali (as well as with caustic soda), nothing was used; the color sequence of darkening completely repeats the description of oxidation using an industrial method: pure copper - brown tint - brown - black - black with violet. In addition to simplicity, accessibility and safety, this household method of oxidizing copper with baking soda has a very interesting and important advantage over the industrial method of blackening with caustic soda: the formation of an oxide film in a soda solution is very slow, which means it is very easy to obtain the desired color intensity and uniformity of film application! Overexpose or overheat/underheat the solution, do not maintain the proportions as in industry - you have to be a complete idiot, the shade scale is plus or minus 1-2 hours of exposure. It is enough to stir the solution (mix, shake) 3-4 times a day to achieve a uniform color of the entire surface. I ended up with a very beautiful piece, uniformly painted black with a purple tint.
2) the discovery of N2 is even worse (of course, for smart people this is not a discovery, but nothing like this was found on the Internet) and was done “at random” or “what if”, in general, destroying the film on copper turning it into pure pink copper even faster and easier, using the same baking soda (teaspoon) + table salt (teaspoon), about 100g of water: place copper in this mixture, stir and after a few seconds the copper is as good as new!
I am posting a photo of a copper tube oxidized for 2 days in a saturated soda solution and a washed tube in a soda + salt mixture.
If these ideas help someone make an efficient solar collector that is not much inferior to industrial analogues, save a lot of money and halve Gazprom’s heating bills, then I haven’t spent time on this thread in vain..
I hope these questions are still of interest to someone else.

Ready minted the composition can be left natural metallic color the original plaque, but you can also “age” it, darken it, subject it to chemical treatment, followed by grinding, polishing, and, if necessary, varnishing it.

Some chemical reactions lead to the formation of metal oxides and oxides, i.e., oxygen compounds, on the surface of the plaque. This process is called BY OXIDATION.

Methods of decorative finishing of metals and alloys

Let us now turn directly to recipes and methods for decorative surface finishing of the most common and easily accessible metals and alloys.

PATINATION and OXIDATION of copper

To change the color of a reddish metal, they most often use PATINATED liver sulfur and ammonium sulphide or BY OXIDATION nitric acid.

PATINATION sulfur liver

The composition of sulfur liver includes potash and sulfur. Sulfur is flammable and therefore requires careful handling. Its vapors with air form explosive mixtures. Sulfur should be stored in a dry place, isolated from oxidizing agents (sulfuric acid, potassium permanganate, berthollet salt). Doses of potash and sulfur may vary. Most often, 1 part sulfur is mixed with 2 parts potash. Sprinkled together, both powdered substances are thoroughly mixed, placed in a metal vessel with a handle and set to heat. It is recommended to stir the contents of the vessel. Fusion of the reagents occurs within 15-25 minutes. The reaction produces a dark mass of liver sulfur. High temperatures cause sulfur to smolder with a blue-green fire. This shouldn't be a cause for concern since patination the properties of sulfur liver will be preserved. The finished hot mass is poured with water, in which the resulting melt dissolves. The water takes on an intense black color.

Pre-treated copper products are dipped into a hot aqueous solution of liver sulfur. If the leaf is large and does not fit into the vessel, it is watered on top with a solution or lubricated with a soft brush.

Copper turns black very quickly. From the interaction of sulfur ions with metal, copper sulfide is formed. This salt is black in color and insoluble in water and dilute acids.

The reaction is faster and PATINATION It will be of better quality if the plate is preheated. In this case, you should not use an open fire, but an electric stove. Then the plate is washed in warm running water and the convex areas are lightly wiped with pumice powder. The color is black in recesses, greyish on inclined surfaces, and shiny red copper on protrusions. An antique imitation is created.

An aqueous solution of liver sulfur can also affect items made of silver or galvanically plated with silver. They are also covered with a black coating.

If PATINATED If the product is not embossed, but a product with a pattern made of hot enamel, it is not recommended to cover the entire surface with a solution of sulfur liver, as clouding of the enamel gloss may occur. In this case, the product is, as it were, painted with a brush in those places that you want patina.

It is recommended to use liver sulfur solution within 24 hours. Sulfur liver can be prepared for future use and consumed in small doses. The melt of sulfur and potash is poured onto a non-flammable surface, cooled, and then broken into pieces and stored in a vessel with a ground stopper. Prepare a liver solution at the rate of 5-20 g of powder per liter of water.

PATINATION ammonium sulphide

Blackening of the metal is observed when patination of copper ammonium sulphide. 20 g of ammonium sulfide is diluted in a liter of water. The product is dipped into the resulting solution or poured on top and wiped with a brush. The work is carried out in a fume hood. Sulfur ions present in an aqueous solution of ammonium sulfide interact with copper ions. Black copper sulfide is formed.

Intensity patination Plaque on metal can be of different shades, from light brown to black. Adjust the color by changing the heating temperature of the plate before patination. If you need to clean the product from the natural color of the metal, do this: dip it in a mixture of nitric and sulfuric (10-15%) acids. Sulfuric acid is added to nitric acid to increase the concentration, since it has the property of attracting moisture. When concentrated sulfuric and nitric acids are mixed, a reaction occurs that releases a large amount of heat, and thick-walled vessels may burst. Therefore, you need to use only thin-walled chemical containers. A copper plate immersed in a mixture of acids instantly disappears. patination film and the black color disappears.

The following precautions should be observed when working with concentrated acids:

• pour them through a funnel under the draft;
• When diluting concentrated acids, pour the acid in portions into water and mix lightly.

Nitric and sulfuric acids are particularly dangerous substances. They cause severe burns. It is recommended to store acids in glass containers away from flammable materials.

You need to work with them only under supervision. If safety regulations are followed, working with chemicals does not pose a threat. All cases of injury are usually associated with violation of the rules.

If drops of concentrated acid do get on exposed areas of the body, you need to quickly wash the burned area with plenty of water (put it under the tap), and then wipe it with a 3% solution of soda or a 5% solution of sodium bicarbonate or baking soda.

OXIDATION OF COPPER nitric acid

This method is simple and reliable, but requires caution, since the work is carried out with concentrated acid. Using a piece of cotton wool tied to a wooden stick or clamped with tweezers, a layer of concentrated nitric acid is applied to the surface and the plate is heated. As the temperature rises, the color of the surface changes from greenish-blue to black. The metal relief is covered with a uniform blackness. The cooled product is washed under the tap, and then the convex elements of the composition are highlighted for greater expressiveness. To do this, a piece of felt or thick wool is moistened in gasoline, rubbed with GOI paste and rubbed with pressure several times. front side metal product. Then wipe dry with cloth. It should be remembered that copper salts are poisonous even if the dust is inhaled. Therefore, after work, you need to wash your hands thoroughly.

PATINATION and OXIDATION of brass

Brass has a range of shades obtained by chemical treatment, very large: yellow, orange, red, blue, purple, blue, black. Moreover, a variety of colors can be achieved on the surface of one plaque.

Along with intense, bright, chromatic colors, brass can be patina in achromatic, light or dark gray and black tones.

PATINATION using sodium trisulfate and nitric acid

0.5 liters of hot water is poured into an enamel, plastic or nylon bowl and 20-30 g of sodium trisulfate, better known as hyposulfite (fixer for photographic film), is poured into it.

If you add a little (about two thimbles) of some acid, such as nitric acid, to this solution, the smell of sulfur dioxide appears and after a while the clear liquid becomes cloudy yellow with a slight green tint from the released sulfur. Validity period patination the solution is very small, only 15 minutes. Brass is dipped into the solution and the surface is observed to darken. A plate preheated in a stream of hot water and dipped into the solution quickly darkens, acquiring grayish-blue or brownish-violet shades, replacing one another.

Patinated The plate is removed with tweezers or hands wearing rubber gloves, and, after washing in hot water, the entire metal plane is wiped with a brush and sand, as if applying a chemical primer to the background. The plate is then dipped back into the solution to obtain the final color. Changes in the color of the plate are observed by slightly tilting the vessel so that metal can be seen from time to time from the opaque solution.

When the desired color is achieved, the product is removed, washed in hot water and, taking pumice powder on wet fingers, very carefully (the film is very fragile) wipe the convex places, exposing clean metal. Pumice easily removes patina from a wet plate. Wash off the pumice powder with water.

After drying in sawdust, the product seems to be dusted with a cloudy coating. To return coinage metallic luster, it is wiped with sewing oil or coated with colorless varnish. The product can be considered finished.

PATINATION a mixture of solutions of sodium trisulfate and lead acetate or lead nitrate

This way patination allows you to get all the rainbow shades on the surface of a brass product: yellow, orange, crimson, purple, blue.

PATINATION goes as follows. 130-150 g of sodium trisulfite are dissolved in one liter of hot water. In another vessel, 35-40 g of lead acetate or lead nitrate are dissolved in the same amount of water. Both solutions are poured into one container. The solution is heated to 80-90 o and a bleached, etched in nitric acid and well washed brass plate is lowered into it. On the surface of the metal, shades quickly change: yellow turns into orange, which, in turn, gives way to red-crimson, then purple. Then the plate gradually turns blue, twitches with a grayish coating, turns black, and the reaction stops. All of the colors listed appear continuously. The lifetime of each of them is short. Therefore, as soon as the desired color appears on the plate, it should be immediately removed, washed and dried.

If the product is removed from the solution, rinsed, and then dipped in some area again into the solution, then removed again, rinsed and dipped in again patination mixture, you will get interesting rainbow colors with relatively sharp transition lines. If the product is removed from the solution gradually, the colors will gently transition into each other. You need to know these methods in order to achieve the intended effect.

Change in color of brass under the influence of antimony chloride

Not everyone likes bright colors on metal, and they are not always appropriate. Sometimes the metal just needs to be blackened. For this master coinage Antimony chloride is used quite widely. It is applied with a brush to the finished plate and rubbed with a brush or stiff brush.

It must be kept in mind that the more solvent there is coinage, the blacker the patina will be (from combustion products ingrained into the metal). If you need to get a slightly darkened relief, coinage wipe evenly with a bristle brush dipped in solvent. To get a completely black coating, the embossing is not wiped, but moistened generously with a solvent. At the same time, excess solvent is removed from the protruding parts of the relief with a dry cloth. Only in deep places are shallow puddles left. Coinage in this case, place it horizontally (so as not to drain the solvent) and burn it for 4-5 minutes with a blowtorch. The flame must be constantly moved across the entire plane, since aluminum is destroyed by strong heating.

When coinage cools down, highlight the bulging areas. They are wiped with a cloth moistened with sewing or other powder mixed with fine abrasive powder. Instead of abrasive powder, you can use abrasive dust that accumulates in the trough under the sanding wheel. After that coinage you need to thoroughly wipe with a dry cloth, removing traces of powder. In appearance and durability, patina does not differ from chemical patina. This method is much safer, since craftsmen do not have to handle concentrated acids.

As for the chemical method of blackening aluminum, there are still no stable, generally accepted recipes. PATINATION And OXIDATION. The simplest and most reliable is tinting according to a recipe developed by the department staff artistic metal processing Moscow Higher Art and Industrial School (formerly Stroganov School).

In one liter of concentrated hydrochloric acid, with constant stirring, dilute 200 g of copper acid bath electrolyte. In this solution patinated aluminum. When immersed in solution aluminum embossing the liquid becomes very hot, seethes, boils. Hydrogen bubbles are released. Coinage quickly becomes covered with a thick black-velvet coating. During operation, the solution weakens. It needs to be updated periodically. Blackening occurs quickly, violently, actively, in a matter of seconds. Remove the product, rinse well in a warm, running water, wipe with a wet foam sponge with quartz sand or pumice powder, removing excess niello from protruding reliefs. The raised areas become a dense gray, and the low areas darken to a matte black depth. Coinage becomes like antique blackened silver.

In order to reveal the noble, black-gray surface of the oxidized relief, the edges are sanded clean and polished. The sparkle of the polished end and the matte surface create an expressive effect. The product, dried and rubbed with machine oil, can be considered finished.

PATINATE And OXIDATE not only is it possible embossed reliefs. These processes are similarly used in a wide variety of applications. artistic metal processing for decorative design of products.

Scunc 10-02-2015 14:14

Health and success to all!
Please share your experience of who inked the copper, I used the search, but I want to ask who personally did it.
Is it possible to obtain a stable (cannot be washed by hands) black color and with what?
Preferably from available materials...

Max_CM 10-02-2015 14:19

You can erase everything.

take the copper in your hands, run hot water from the tap, and rub the copper with ointment under the stream.

sansem80 10-02-2015 14:22

quote: Originally posted by Max_CM:
... from the tap, hot water, and rub the copper with ointment under the stream.

Oh, how. Otherwise, I applied this ointment to dry and cold copper, but nothing really inked.
Doesn't the ointment wash off under running water? What should I rub it with? A rag?

vladimir c 10-02-2015 14:30

I tried simply rubbing it with my finger on cold finely dispersed sulfur (sold in gardening stores) - it turned black.

Vitaly B 10-02-2015 14:36

quote: Originally posted by Max_CM:

At the nearest pharmacy sulfur ointment 3kop price.

I did it differently, I spread a layer and put it on the hot body of a table lamp, or I blow it with hot air with a hairdryer and everything turns black, not bad, in 3-5 minutes, although I did it on silver, copper should darken faster. Afterwards, wash everything with acetone or soap...
------------
Best regards, Vitaly.
www.vitaliknife.ru

Scunc 10-02-2015 14:37

Here I use sulfur ointment and ink, it turns black well, but the ink is easily erased completely, I wonder about the jet, what does it do?

Max_CM 10-02-2015 14:44

It just heats it up, it’s more convenient for me, just with my fingers, Vitaly puts it on the lamp, it doesn’t matter how the main thing is to heat it up.

Visiter 10-02-2015 14:45

Sodium thiosulfate (10 ml ampoules from the pharmacy, inexpensive) + any acid (I made it with acetic acid). Pour thiosulfate, add acids until the color of milk and the smell of hydrogen sulfide are obtained, lower the copper (bronze, brass, etc.). Color depending on exposure, quite quickly.
They gave me good advice on sulfur ointment; I applied it cold, but it didn’t help.

niks78 10-02-2015 15:07

When I stained the oak tree in ammonia and put the copper tire on it, it turned black with a blue tint. I haven't tested the durability

vityuxa 10-02-2015 15:43

Nestor74 10-02-2015 15:53

quote: http://www.medwed-hunt.ru/Good...atalogBegin - here there is an excellent blackening agent.

Really
Look for BrassBlack in gun stores - I haven't seen anything better yet. The effect is immediate. Blackens copper, brass, bronze, silver. What other sulfur ointment? We must keep up with the times. All my works are patinated with this liquid.

Trident8 10-02-2015 16:00

Sulfur liver: mix sulfur (taken from a veterinary pharmacy) with soda 1:1, stir until brown, dilute slightly with water - and go, cheap and cheerful.

niks78 10-02-2015 16:39

and when I stained the oak with ammonia, I laid the copper busbar down and it turned black

Androniy 10-02-2015 16:53

I wanted to darken the copper coin only slightly, but the slightest application of sulfur ointment immediately resulted in a dark brown coating. I found a solution - add a little sulfur ointment to a large amount of Vaseline. Then I applied it to the fabric and rubbed it vigorously. The result was a light brown patina.

Max_CM 10-02-2015 17:03

quote: Originally posted by vityuxa:
1470.0 rub. for 90 ml. Six, or even seven funfairs of vodka! Question about durability, is it worth it? how about erasability?, from time immemorial it was inked with sulfur liver, (since the 16th century) since it has come down to the present day, the bicycle was not invented. I tried it. But you definitely need to take Potash (POTASSIUM carbonate), specifically, with baking soda (SODIUM carbonate) the effect is not the same, it is less stable, and the coating is time-to-time. That’s not bad; coat the cleaned, fat-free part with a brush with nitric acid, the amber is not comme il faut, but not really, in the common fund at the station it’s worse. And immediately heat it up, you can get a very diverse color, but it takes some skill. With both acid and sulfur liver, the coating can only be erased with fine sandpaper or sanding paste. I will sign every word, since I myself was bothered by this ink idea.

www.chip-dip.ru sera fic knows it, I’ve been to all the pharmacies, it turns out it’s only available where the medicines themselves are prepared in production facilities,
I begged for a teaspoon, ran home and quickly cooked!
I came across a stainless steel ladle and the blackening still remains on it! It stinks! I thought the neighbors would call the Ministry of Emergency Situations right now!
The ink is great, I don’t remember the stability on copper, but it washes off easily from silver, and unfortunately, this brew is not stored, it decomposes, you have to brew it again every time. In!

hunter1957 10-02-2015 18:51

quote: Yeah! about two or three years ago I got confused with sulfur liver, potash at www.chip-dip.ru sulfur fic knows it, I went to all the pharmacies, it turns out it’s only available where the medicines themselves are prepared in production facilities, I begged for a teaspoon, ran home and quickly cooked! It's a stainless steel ladle and the blackening still remains on it! It stinks! I thought the neighbors would call the Ministry of Emergency Situations right now! The ink is great, I don’t remember the stability on copper, but it wears off easily on silver, and unfortunately, this brew is not stored, it decomposes, you have to brew it again every time. In!

In Ruskhime it will be cheaper to take chemistry.......

Scunc 10-02-2015 20:45

Is this liver stored for future use?

vityuxa 10-02-2015 21:29

quote: You have to cook it again every time. In!

The solution sits in the refrigerator for a month, the secret is simple, just right up to the neck, just try with a “slide” so that it pours out from under the cork when twisting, it works fine, although when it’s cold it’s slower. The boiled powder will lie as long as you like, without moisture, I also put small bags of silica gel for medicine in my vitamin bottle. And there are also some nuances: first melt the sulfur and pour it out, well, it stinks, of course, the main thing is that it doesn’t dry out, it’s not scary, but it stinks more, and only then slowly sprinkle in the potash and stir. I made 1 sulfur 1.5 potash. A good correct powder only came out after 4 times, then the sulfur did not dissolve, then it was kind of shitty, in lumps. Well, fuck it, you have to do it and that’s it! You can’t stop it...

i_vb 10-02-2015 22:16

I don’t make knives en masse, but I do a lot, with copper elements even less often. I use the aforementioned BrassBlack. The same applies to cupronickel. A bottle costs 700 rubles, not 1600, at least in Moscow. I don’t know how long it will last, but 3 years, about 20 different parts - a third of the bottle. This cannot be removed with a sheath or hands, but with a zero - it’s easy, however, like the vaunted liver.
PySy: If there is a cat in the house, throw a bolster made of copper or brass into his toilet for a day, I guarantee old bronze. Moreover, even with a zero you won’t be able to pull it off right away. But - a little divorced. Verified.

vityuxa 10-02-2015 23:00

Here's from the chemists: they are certainly impartial. http://chem21.info/info/18373/ Products made of copper and its alloys can be painted in colors from gray-black to black-brown by oxidation in solutions of ammonium sulfide or sulfur liver. The so-called liver of sulfur is a mixture of various potassium polysulfides with potassium thiosulfate. Sulfur liver is obtained by fusing sulfur with potash for 15-20 minutes. Various recommendations suggest fusing 1 part (wt.) of sulfur with 1-2 parts (wt.) of potash (potassium carbonate K2CO3). Sulfur is melted in a porcelain cup, then dry potash is gradually added to the melt with constant stirring. When air enters, interaction occurs between the components of the melt and a brown viscous mass is formed  

quote: Works on almost all "tsvetnina" tested

I wasn't too lazy to count. I treated 100 knives with this liquid, I didn’t use half of them (!!!) 100
How else can you be convinced?

vityuxa 11-02-2015 13:25

quote:

No San, I’m not greedy, I’m ideologically fucked up, and I don’t believe in anything until I figure it out myself, or I don’t do it, but I’ll keep doing it until I succeed... And my sons will buy vodka if they do, no problem .

Scunc 11-02-2015 17:06

BrasBlack is interesting, I just stopped at first by the price and availability, then I looked... sulfur is in bags at work, thiosulfate is sold in the pharmacy, i.e. In any case, some hemorrhage. You can't just buy it in a store(
But I have identified three main options for myself, so I will move in this direction, whichever is the first available will be where I will start)
And thanks for the advice! I needed personal opinions.

L.E. 11-02-2015 18:04

quote: Originally posted by i_vb:

The bottle costs 700 rubles

GM63 11-02-2015 19:50

Vityukha is clear, it’s more important for him to buy vodka, he’s cringing))

How else can you be convinced?

Alexander.

Scunc 11-02-2015 21:17

Sodium thiosulfate is a prescription drug(

Scunc 11-02-2015 21:24

quote: Originally posted by GM63:

Alexander.
I didn't even understand. On the contrary, I say that I am against this collective farm with sulfur acids and the stench in the kitchen.
But just to buy a special liquid “Noirit” in Nozhinsk for 400 rubles per 100 ml. and use it, because it blackens and ages almost any metal color, and brass-copper generally looks black.
True, when ordering, you need to remind them to check the packaging. Last time I ordered, half of it leaked out.
Somehow you misunderstood me apparently

i_vb 12-02-2015 12:24

quote: Please tell me where you got it in Moscow?

I wrote that I took it a long time ago - two years ago. 560 rub.
Last time I saw it in a hunting store on Kalanchevka for 750 rubles. before the New Year.
If I don't forget, I'll come and have a look.
And so - in hunting stores. The idea with the cat was ignored in vain - it works for free!

GM63 12-02-2015 01:00

quote: Originally posted by Scunc:

I'm looking for now (BIRCHWOOD CASEY 15225 BB2 Brass Black Metal Touch-Up) that's what it's called correctly.

What to look for here...
Any gun shop has it.

RashchektaI 12-02-2015 08:31

quote: Originally posted by Nestor74:

I still don't understand about BrasBlack. Religion doesn't allow it? Where else with goodness?
There is no need to add any stink or acid.... I unscrewed the cap, dipped the brush, anointed it, twisted it... No dancing with a tambourine...
Vityukha is clear, it’s more important for him to buy vodka, he’s cringing))
I wasn't too lazy to count. I treated 100 knives with this liquid, I didn’t use half of them [b](!!!) 100

At least that's enough for that much longer.
How else can you be convinced?

About thiosulfate. It works in hot water with the addition of hydrochloric acid. It is needed as a catalyst. It will not work with acetic acid. I already checked)))
The product must be immersed in hot solution for a few minutes. Those. This option is not convenient for us. You can’t put a ready-made knife there, but you can blacken the part separately, but then during installation you’ll tear it off, scratch it...

If you just smear it with a thiosulfate solution, it won’t turn black at all. barely... it's not work. Just frustration.

What an apologist you are for Brasblek. When you need to make a hundred knives and the cost of one costs 30 rubles, then it’s easier to buy, but when you make one knife a year with copper, it’s doubtful. As for the acid, I didn’t try it well, but it works great with vinegar essence. BUT nitrogen or sulfuric acid is preferable.

111StS111 12-02-2015 10:04

Blackening agent for bluing Raven3. Blackens steel, cupronickel, copper, bronze, brass. I haven't tried stainless steel. Doesn't take silver. The coating is quite durable.
Costs 200 rubles.

The surface of an aluminum object is first polished with the finest emery powder.

Then grease with olive oil, and heat with frequent lubrication with this oil, over an alcohol lamp until the olive oil turns black.

After this, the heating is stopped and after the object has cooled, wipe off the oil with a rag.

Black mordant for iron and steel:

Burnishing of iron and steel, which has as its goal, on the one hand, to give the surfaces of these metals a beautiful appearance, and on the other, to protect them from rust, consists in the fact that metal surfaces, thoroughly polished and cleaned of grease and dirt, are rubbed with various mixtures of appropriately selected substances and are then exposed to high temperature.

Here are some practical and fast-acting bluing compounds;

1. 1 part silver nitrate (lapis), 500 parts water;
2. 1 part antimony chloride, 1 part olive oil;
3. 2 parts antimony chloride, 2 parts ferric chloride (crystalline), 1 part ink-nut acid;
4. 54 parts copper sulfate, 3 parts iron filings, 14 parts nitric acid, 26 parts alcohol, 200 parts water.

Black mordant for copper:

Prepare a saturated solution of copper sulfate and add ammonia to it until the mixture takes on a bright transparent blue color. The item being treated is dipped into this solution for a few minutes, then removed and slightly heated until it turns black.

Another method is to clean the copper item to be blackened first with fine sandpaper, after which try not to touch its cleaned surface with your hands.

It is then either immersed in a liquid solution of platinum chloride or moistened with it using a brush. This solution, if it does not have an acidic reaction, is slightly oxidized with hydrochloric acid.

A very durable blackening of copper products is obtained by immersing them in a saturated solution of copper metal in nitric acid and then heating it slightly.

Black mordant for bronze:

Typically, both pure black and gray coloring is obtained by the formation of copper oxide or copper sulfide on the surface of the item. But both of these stains can also be achieved by deposition on the surface of the item of sulfur compounds of other metals - lead, bismuth, mercury and others. Will the coloring be completely black or light black, i.e. gray, depends both on the composition causing the coloring and on the time of action of the latter.

To form black copper oxide on the surface of things, the heated item is immersed for a few seconds in a solution of copper in excess of nitric acid, and then held over a charcoal fire until its surface begins to turn black.

To obtain a uniform and sufficiently thick black color, the operation is repeated several times, otherwise the color will not be completely black, but grayish. After dyeing is completed, wipe the item with a cloth soaked in oil. This is how optical instruments usually become blackened.

For brass and bronze, you can use the following solution: 2 parts arsenic (not arsenous) acid, 4 parts hydrochloric acid, 1 part sulfuric acid and 80 parts water. Arsenic acid can be replaced with antimony oil (antimony trichloride). The item is immersed in a solution heated to 50 degrees Celsius, and during immersion, it is touched with a zinc stick.

Dissolve 45 g of lead sugar (lead acetate) in 3/4 liter of water, and 150 g of sodium sulfate (hyposulfite) in 1/2 liter of water. Mix both solutions and heat to 85-93 degrees. The surface of an item immersed in the solution is very quickly covered with a layer of lead sulphide. The color of this layer changes as it thickens and eventually becomes a very beautiful metallic gray.

Black mordant for silver:

Blackening is a widespread and almost the only practical method of coloring the surface of silver or silver-plated things, and not the entire surface of the thing is painted black, but only some of its parts in the form of various figures, patterns, etc. This kind of decoration of silver objects with niello has been known for a very long time.

The blackening process involves the formation or deposition of silver sulfide on the surface of a silver item. In a makeshift way blackening is done chemically; The in-depth patterns engraved on the surface of the item are filled with a fusible compound that includes silver sulfide, then the item is exposed to high temperatures sufficient to fuse the compound with the silver.

In short, the surface of the item is partially covered with “black enamel”, the composition of which is different.

Here is one of the good recipes for such black enamel: 38 parts of silver, 72 parts of copper, 50 parts of lead, 384 parts of sulfur and 36 parts of borax are melted in a crucible, and the metals included in the composition are converted into sulfurous ones. After cooling, the alloy is crushed into a fine powder and carefully sifted.

When used, the engraved areas are sprinkled with enamel powder and the item is kept on fire until the melted enamel fills the indentations again.

After cooling, the excess enamel is washed off, the item is sanded and polished. Sometimes silver or silver-plated things (vases, figures) are blackened with graphite. To do this, they are lubricated with a paste-like mixture of 6 parts of powdered graphite and powdered bloodstone with turpentine (bloodstone or crocus is native iron oxide).

When the lubricant has dried, the item is wiped with a soft brush and suede, then its convex places, to give them greater shine, are rubbed with a cloth moistened with alcohol or vodka.

Such blackening is purely mechanical and is determined by the same conditions that, over time, produce contamination of any metal surface; adhesion of dust particles to surface irregularities and roughness.

Consequently, the less smooth the surface, the more successfully blackening it by this mechanical method is achieved. This blackening is not as durable as chemical blackening.

Read also:

Let me make a reservation right away that I am not a chemist, and all my knowledge is only what I have left over from school. Therefore, the recipe was not fully followed and some deviations were made.

Bluish-black color.

Treatment lasts 25-30 minutes. at a temperature of 15-30°C.

Preparation of copper carbonate.

IN in this case When recipes mention copper carbonate, they are actually talking about basic copper carbonate. To obtain it, you can use copper sulfate, acetate or nitrate. A solution of potassium or sodium carbonate (potash, soda) is added to an aqueous solution of one of these salts. The green-blue precipitate that falls consists of basic copper carbonate of variable composition, nCuCO 3 x mCu(OH) 2, where n and m can vary within some limits, which for us, in this case, is not very important. The precipitate is filtered off, washed with water and can be used.

The process itself.

To blacken brass using this method you will need:

• copper sulfate;
• baking soda;
• ammonia;
• two glass jars, preferably the same volume;
• filter paper or something similar;
• stirring stick.

The vitriol was purchased at the nearest hardware store in the department that sells all sorts of pesticides to combat garden pests.
Soda - in the nearest grocery store, where there is simply plenty of it.
Ammonia - at the nearest pharmacy. But only 10%. As they explained to me, 25% is not for sale due to its danger.

	First we prepare copper carbonate. For this we need copper sulfate and ordinary soda.
	Dissolve the vitriol in warm water. The solution needs to be saturated, i.e. add vitriol until it still dissolves. The solution must be made so that it occupies only half the container.
	Then slowly, a little at a time, add soda to the saturated vitriol. It is precisely because the solution begins to bubble like soda that I recommend making vitriol in only half the container.
	Stir. Over time, the seething subsides. I poured baking soda until the bubbling stopped. After a while, you will see that you have obtained a finely dispersed suspension of a pleasant turquoise color. On the surface you can see that the fry are still seething there.
	Now the resulting suspension must be filtered. There was nothing worthwhile at hand except napkins. The recipe says to dry it. But I didn't do this.
	Now we need a 25% ammonia solution. As I already wrote, only 10% is available in the pharmacy. This is what we will use.
	Little by little add turquoise porridge to ammonia. The solution turns blue.
	We also need a saturated solution. Therefore, we add, without sparing, copper carbonate. You will end up with a blue-black liquid. This is what we need.

The solution is ready, all you have to do is put it in there necessary details. Blackening time, according to the recipe, is 25-30 minutes.

If the part is kept in the solution, copper carbonate will settle on it in the form of turquoise crystals, which, in principle, can then be easily scraped off with a fingernail without damaging the blackening;

If you have difficulty removing blue sediment from a part, I recommend simply heating it in the flame of a candle or lighter. The sediment will immediately fall off on its own.