How to Blue Metal Knife Using House Chemicals

Burnishing or oxidation is a method of surface coating (finishing) of metal products in blue, black, blue-black or tint colors by exposure to them chemically and thermally.

It is used for the purpose of corrosion protection of metal products, and also gives the surface an attractive tint. There are many ways to surface tint metals. The main one is the creation of an oxide film.

The most common are chemical (alkaline and acid) and thermal effects on the surface. As a result of this treatment, the chemical composition and structure of the surface layer changes. Outwardly, this is manifested by the formation of a film in the form of metal oxide.

You can independently perform coverage using simpler technologies.

Common household methods of protecting and decorating metal surfaces include:

boiling parts in special chemical compositions that you can prepare yourself;
oil coating followed by heat treatment;
applying to the surface of the finished product with a brush.

Carrying out work during chemical burnishing is associated with chemical etching and cleaning operations, as well as with mechanical grinding and surface wiping.

In order to apply burnishing at home using chemicals, you need to create certain conditions:

provide the working room with ventilation or exhaust;
prepare a container of neutral material that is not destroyed by the action of chemicals. A vessel made of heat-resistant glass, earthenware or porcelain is best suited. If long boiling of the solution is required, then a stainless steel container can be used;
the container must have a sufficient volume so that the part is completely covered with the composition;
stock up on protective equipment: gloves, face shield or goggles, aprons.

Features of chemical burnishing and recipes for some compounds

Before performing work, the surface of the metal product is subjected to treatment: removal of the old oxide layer by sanding and degreasing with a solvent.

Persistent burnished coating is mainly formed in a boiling solution throughout the entire staining cycle. To obtain a strong film, the process should last from 30 minutes to one and a half hours, therefore, the boiling solution is periodically added to ensure complete coverage of the part.

After the end of the process, the part is thoroughly washed with detergents, and then lubricated with oil.

For homework, they mainly use the alkaline oxidation method. Consider some options for the chemical oxidation of metals in an alkaline environment.

Method number 1:

Water is poured into a container (porcelain) of an appropriate size and sodium nitrate (sodium nitrate) and caustic soda (sodium hydroxide) are dissolved in it in a ratio of: 100 ml of 30 g of sodium and 100 g of soda.
The mixture is heated to 140-160 ° C, and the workpiece that is placed there for at least 30 minutes is placed in it.

With the right process, you get a deep black finish, sometimes with a bluish tint.

Method number 2:

A bluish tint of the film can be obtained using a boiling saturated alkaline solution in which a high concentration of potassium or sodium hydroxide is dissolved. At least 700 grams of a chemical is dissolved in 1 liter of water.

These recipes are given as an example. There are many other chemical compounds using nitrites and nitrates.

Oxidation in an acidic environment is carried out at lower temperatures. For example, when using an acid solution consisting of:

calcium nitrate - 30 hours,
phosphoric acid - 1 h,
manganese dioxide - 1 h.

Oxidation is carried out, keeping the workpiece in solution for at least 30-45 minutes at 100 ° C.

Metal Burning Products

Simple coating methods that you can use at home include surface coating technology for oil, nitrate, and Clover.

These burnishing agents are available to use and allow you to carry out work at home without much preparation.

Consider ways to create a film using each of them.

Oil coating

The technology of creating a protective film using oil is the most common for home use.

It is carried out as follows:

the skinned and fat-free product is covered with machine or sunflower oil;
then it is placed in the oven and heated to 350 - 400 ° C;
after cooling, the surface of the part becomes brown or black;
the remaining oil from the part must be removed with a rag;
to obtain a more saturated color, the process should be repeated several times.

You can use different oils, for example, weapons, linseed or olive. You can apply it with a brush or by dipping the part in an oil composition.

If you want to blacken on any part of the part, then for this it is better to use firing using a blowtorch. In the process of such firing, a color change in the surface of the workpiece is clearly visible. Upon reaching a saturated brown - black color, heat treatment can be stopped.

Using saltpeter

A good result of chemical burnishing is given by a classic solution using nitrate in addition to those given earlier. As a result of digestion of a part in a solution of sodium nitrate at a temperature of 130 - 150 ° C, a strong oxide coating of a shiny black and blue hue is obtained.

Recipe composition with nitrate:

Distilled water - 1 liter;
Sodium nitrate (NaNO3) - 500 g;
Caustic Caustic (NaOH) - 500 g.

For sale are ready-made kits with nitrate for oxidation.

You can watch the process of burnishing in nitrate in the video:

The surface during this treatment looks smooth and does not require additional polishing.

Surface treatment with Clover

It is possible to process the metal surface with the ready-made Clover tool. It has a gel-like consistency and is sold in small 50 ml containers.

Use it for minor corrosion damage to the metal. To get the maximum color of the product, you need to process it with "Clover" two to three times. Before applying it, the part must be sanded and degreased.

The tool is applied with a brush and incubated for 2 minutes. When a whitish-yellow coating appears, it must be washed off with warm water, and wipe the surface dry with a cloth.

The advantage of this tool is its ease of use, which is why it is often used to cover weapons. On steel containing more than 3% Cr, it has no effect.

Cold burnishing at home

The use of Clover means does not require additional heating of the workpiece, therefore, the method of such processing is referred to as cold. In addition to it, other products are used for cold burnishing at home, which are also applied to the treated surface with a brush.

For example, they use the domestic preparation Voron-3M.

When applied to a metal surface, a dense black film is formed. Therefore, this coating is called blackening of the metal.

Also popular is the imported tool "Paris oxide", which includes selenium.

The drug includes three vials. One composition is intended for surface pretreatment, the second is an active composition, and the third provides protection for the formed coating.

The solution is also applied to the product with a brush, after receiving the color, the residues are washed off the surface with warm water.

Cold processing is used for small parts. Especially with the help of this method, it is good to burn the gun, since the method of hot boiling in chemical solutions cannot be applied to it.

Steel burnishing at home

The question of how to make steel burnishing at home is of interest to many.

Most of the parts that are burnished belong to steel products. Therefore, the above methods of treating a metal surface by oxidation and coating with an oil film are mainly used for steel alloys.

Many steel grades are susceptible to rust. The coating for steel products primarily serves as a protection against corrosion and at the same time gives them an attractive appearance. The degree of protection and color of the oxide film depends on the thickness of the layer and the reagents used. Thickness can vary from 1 to 10 microns.

When bluing steel products in a chemical way, the choice of solution components when using heating to high temperatures should be approached with caution. For example, there is a ban on such processing of hardened parts, as well as steels that cannot be heated to high temperatures. This can lead to a deterioration in their technological properties.

For this reason, if high heat treatment is required, alkaline solutions are recommended. They are more gentle.

Oxidation in acidic formulations is carried out at lower temperatures. For example, when using an acid composition consisting of:

calcium nitrate - 30 hours,
phosphoric acid - 1 h,
manganese dioxide - 1 h,
carry out oxidation at a temperature of 100 ° C, keeping the part in solution for at least 30-45 minutes.

Black metal

When heating steel preforms in an acidic or alkaline environment, a film of different shades can form on the surface. Burnishing includes all the colors characteristic of the discolouration. They change as the film thickness increases from yellow, brown, purple, then to gray, blue and black.

To give a presentable appearance and protection against rust, metal burnishing is used. At home, this procedure is quite simple, if you know the basic ways to do it.

Using house burnishing is a profitable procedure that saves you a family budget. At the same time, a special composition is applied to the metal, which allows blackening and forming a protective film.

First, the steel is cleaned and degreased, then the surface is processed in the selected way.

Safety regulations:

All work is done with gloves;
The burnishing solution contains various kinds of chemistry, so it should be stored in its original packaging, beware of spilling substances;
Nearby there should be funds from burns, in order to provide first aid if necessary;
Work is being carried out in a well-ventilated area;
It is better not to use metal utensils when working.

You will also need sandpaper. It is used for cleaning surfaces. The metal is usually degreased with acetone, perchlorethylene, B-70 gasoline and other organic solvents. Its surface to these substances is inert (immune).

Methods of metal processing

Blackening of metal occurs in the following ways: alkaline, acid and thermal. Such work can be carried out on an ax, weapons and other metal products.

Alkaline burnishing

The most popular method of steel blackening is chemical oxidation with an alkaline composition. The result is quite high quality and stable when strictly adhere to the technology. The method is based on the ability of the metal to oxidize. Work is carried out at 135-150 degrees, you should be prepared for a characteristic smell.

Alkaline blackening is best done outside the apartment. This can be done in the yard or garage, in a room with good ventilation.

So, let's begin. The first step is to degrease and clean the surface of the metal object well. Remember that burnishing at home is impossible without preparing a good alkaline composition.

You can do this as follows:

In a porcelain bowl you need to pour 100 ml of ordinary water.
Add 100 grams of industrial soda and 30 grams of sodium nitrate.
Thoroughly stir and heat the resulting composition to 135-150 degrees.

The solution is ready, now you need to lower the product, which is planned to be burned, into it for half an hour. Then the metal is washed with distilled water, dried and lubricated evenly with machine oil.

As a result of alkaline burnishing at home, a bright black color with a blue tint should appear. To obtain a thicker oxide film, the percentage of alkali in the solution should be increased.

On the video: do-it-yourself alkaline burnishing.

Acid burnishing

Before burnishing, sand the product well with a sandpaper. Then you can degrease it by dipping for 10-20 minutes in kerosene or sodium triphosphate. After that, the part is dried, and at this time you can prepare a solution for blackening.

It is prepared as follows:

In 1 liter of water, 2 g of tartaric and tannic acid are added.
The ingredients are thoroughly mixed.
The solution is heated to 140-150 degrees.

The part should be lowered into the heated composition for 14-17 minutes, then rinsed with ordinary or boiling water (for better cleansing from the solution).

The last step is immersing the product for 60 minutes in engine oil. Then it needs to be wiped, dried and can be used.

Thermal burnishing

This option appeared before everyone else, therefore it is easier to implement than others, but no less effective. The method is based on heating metal products until an oxygen reaction occurs with the metal itself. The power of heating varies depending on the desired result.

The table shows the resulting color at different temperature conditions.

To implement the heat treatment, you will need machine oil (500 ml), a bath for machine oil, pliers, a gas hairdryer and dry wipes. Heat treatment should be done on a brick or other non-combustible surface.

Progress:

The hairdryer must be turned on to the maximum temperature and hold the product over it.
The preheated part is completely immersed in oil, while holding it with pliers.
Remove and blot the product with a napkin.
Repeat 3 more times the whole procedure from the very beginning.

This method will not give the metal a black color. Blacking with this method is necessary to prevent rust; decorative burnishing is rarely done in this way.

Citric Acid Oxidation

Blackening with citric acid protects against corrosion, films of oxides and rust. This is an old method suitable for high carbon steel. If in this way the knife is oxidized, then in the places where it will be sharpened, the entire coating will come off. It is not too persistent, suitable for items that are rarely used.

For this you need:

a pack of citric acid;
hot water (90-95 degrees);
machine oil.

In a container of stainless steel or glass, pour the entire bag of citric acid (20 g), pour hot water (about 200 g) and mix thoroughly. Dip the product into the prepared composition and leave for 50 minutes. After a while, the onset of the reaction can be observed. Around the part, bubbles will actively form. They can interfere with the access of air to the product, so you can periodically (every 10-15 minutes) move the knife so that they disappear from the surface.

After 50 minutes, you can get the part, it will become black at the end of the process. Rinse it, grease it with oil and wipe it.

Blue steel

Hot burnishing often helps to achieve a blue color. This happens when heated for a longer time. At first, the surface acquires white, yellow, purple hues, and as a result, a beautiful blue color is obtained.

Recipe 1

Steel burnishing at home in this way involves the presence of a hearth, ideally with automatic blowing. Birch charcoal should be put in a metal box, leaving room for the metal to be processed.

This design is placed in a hearth previously preheated. The metal is lubricated with vinegar, rubbed and put in a box when the coal begins to smolder. If a bluish color occurs, the part must be pulled out, cool slightly and returned to its place. Such manipulations should be done 3-4 times until the correct shade is obtained.

Recipe 2

This method of obtaining blue is carried out without heat treatment. It will take 3 grams of hexacyanoferrate ("red salt" among the people) and one and a half chlorine iron. Safety chemicals must be added to water, but not vice versa.

These substances dissolve well and are strong oxidizing agents. We add them individually in 0.5 l of water, mix and mix in one substance. We dip steel into the resulting solution until it acquires the desired color.

Noble gray and black colors

A beautiful gray color can be obtained using nitrogen copper (a type of salt) and denatured alcohol (a type of alcohol). At the same time, a rather powerful film is formed that is well resistant to rust. Salt (70 g) should be melted on a fire, add methylated spirit (20 g) to it and grease the metal with this mixture, heating it until it gets the right color.

You can blacken stainless steel using different oils (linseed, animal) or wax. They lubricate the subject and heat it on fire. As a result, it becomes a noble black color and a stable protective film appears.

How to carry out the burnishing (2 videos)

Methods of metal burnishing (19 photos)

Hello ladies and gentlemen. Today we'll talk about burnishing, oxidation or blackening of steel. This is a surface coating method for steel with a thin layer of iron oxides. It protects the metal from corrosion, and also gives an attractive tint to the product. You can achieve black blue-black, gray or blue. The process takes place under the influence of chemical (alkali or acid) and thermal methods. I will show a few methods that I personally tested.

Hot burnishing

Let's start with the fastest, and perhaps the most effective way.

We will need:

Machine oil
Degreaser.
Bake.
Whit spirit

The process of burnishing the blade:

We will burn the knife with temperature and oil. I used the machine, but the sunflower will go. The product to be burnished, in my case a knife, must be degreased. I used uyat spirit.

Next, pour the oil into a container, preferably porcelain, I poured into a mug. Immerse the blade in oil, and send the mug into the oven at a temperature of about 280 degrees Celsius. A few words about the stove. Ideally, you need a muffle furnace with temperature control, but where do we get this? A kitchen oven would do, but the room should be very well ventilated. I used a cooling furnace, as well as a cooling stove in the house.

The second option is far from the best, since the oil begins to boil and evaporate, which is accompanied by a not pleasant smell, well, and the evaporations themselves (therefore, the oven is not the best varic). You need to boil the knife for 10 to 20 minutes until you are satisfied with the shade. Here is the result:

After the product has cooled down, wipe it again with a degreaser and wipe it dry. Of course, hardening from this method will not go anywhere.

Bluing in citric acid

A well-known and effective way, but longer.

You will need:

Lemon acid.
Warm water.
Degreaser.
Napkins

Burnishing process:

About 0.5 g of lemon are needed per 0.5 liter of water. I poured 10 grams into a glass of 150 ml. Acid must completely dissolve in water. Next, also degrease the surface of the blade and lower it into the solution. After a couple of minutes, bubbles should form on the product.

Blackening takes from half an hour to two hours. In general, it depends on the steel, but I tried different brands, and for all the result is about the same. Every 15 minutes, the blade must be removed and wiped with napkins, removing black plaque. Once you are satisfied with the color, you can pull out the knife and wipe it with vegetable oil this will stop the reaction.

And yes, the water should be hot 70-90 degrees Celsius. Although I often scored at this temperature, the process went on, but unevenly.

Here are two examples that are completely different from each other.

Differences due to different grades of steel. The one that is darker - high-carbon (the former file), blacking is ideal for such brands. Well, I constantly wiped the blade. The second knife made of low-carbon steel, which I just left for about a day in the solution, and the process went unevenly. In general, I am still satisfied with the result, the tint turned out to be interesting (there is yellowness in the photo, in reality I notice it).

This is another file that turned gray in half an hour.

Vinegar Burning

You will need:

Table vinegar 9%.
Degreaser.

Burnishing process:

Vinegar must be boiled, but you can do without it. It smells so bad, so I scored. But vinegar should not be cold, at least at room temperature. The blade can be washed under hot water so that it also warms up, after which it is degreased and dipped in vinegar, and also every 15-20 minutes clearing black plaque.

After the blade we wipe in oil.

The result is this:

All these methods allow you to oxidize the blade, which will protect it from rust, and also give an interesting tinted color. In all cases, do not breathe the vapors of bluing, they are harmful to health.

All these methods will allow you to achieve any result you need. The coating is strong enough in all the methods described, and it will last for a couple of years for sure. I hope the article was helpful to you.

For some reason, it is believed that metal burnishing cannot be carried out at home, that such an operation is carried out only in factories. In fact, this opinion is erroneous and at home, using simple improvised means, you can not only protect the metal from rust, but also give it a beautiful black or blue color. So, let's take a look at the methods of performing burnishing on the example of a knife.

Home Technology Features

It is only natural that the use of industrial knife burnishing methods at home is neither economically nor technically advantageous. In production, steel burnishing is achieved by changing the structure of the upper layers of the metal using chemicals. At home, the use of this method is impractical; there are much simpler, but quite effective ways to burn a knife at home.

Burning Methods

There are three ways to burn steel:

Cold - when a product subjected to bluing does not experience thermal effects.
Hot - in the process of burnishing, the product undergoes any heat treatment.
Treatment with an oxidizing agent is the most difficult method for home use, since it is necessary not only to use chemicals, but also heat to high temperatures.

Now let's take a closer look at what kind of knife burnishing techniques can be used at home. Before using any of the methods, it is necessary to degrease the steel with alcohol and wipe dry with a flannel.

Lemon acid

Such burnishing will protect the metal from corrosion and give it a beautiful black color. The method of steel burning with citric acid has been used for a long time, but is suitable only for high-carbon metals. In addition, you should be aware that knife burnishing in citric acid is best done when the knife performs purely decorative functions, since such a method of blackening metal is not stable and when sharpening the entire coating will come off very quickly.

In order to blacken the knife with citric acid, you will need:

citric acid - 1 sachet;
water heated to 90 - 95 degrees;
machine oil;

Pour hot water into a glass or stainless dish and dissolve citric acid in it in proportions 1/10, that is, 10 parts of water per 1 part of citric acid. Place the knife in the water and leave it for 50 minutes. Periodically move the knife, as the bubbles formed on its surface will impede the access of air and interfere with the burnishing process. After 50 minutes, the steel should turn black, which means that the burnishing process has come to an end. It remains to rinse the knife in clean water, grease it with machine oil and wipe it dry.

Although this method of burnishing protects the metal from rust, it is more likely to have a decorative character due to the fact that with the slightest impact, the coating comes off and the knife will need to be burnished again.

Coca Cola

Another way to blacken a knife at home is with Coca-Cola. By the way, this drink is very versatile and is most often used not for its intended purpose, namely for all kinds of experiments, including with metals. So, to burn a knife in Coca-Cola, you will need:

glass or metal container made of stainless metal;
coca Cola;

The burnishing process is similar to the previous one, but does not require heating. To burn this way, you need to put the knife in the drink for a day or two, periodically turning it over and releasing bubbles. After this time, it is necessary to replace the drink with a new one and re-place the knife there. This procedure must be performed until the knife acquires a beautiful black color, usually within a week, changing the drink every two days. Make sure that Coca-Cola completely covers the knife by 5 centimeters and do not forget to periodically turn it over, as the bubbles accumulating on the surface of the knife will interfere with the process of blackening it.

After this, it is necessary to rinse the knife well in clean water, you can add soap, and grease it with machine or gun oil. Without lubrication, rust appears on the metal very quickly, it becomes visible already during the drying process.

Such a burnishing method is best suited for narrow, even surfaces, for example, a bayonet-knife burner in this way will achieve a more even coating than on any complex surface with many bumps and bends. In addition to Coca-Cola, you can also use Pepsi-Cola. Blackening occurs due to phosphoric acid, which is part of these drinks.

This method of burnishing a knife is quite durable. According to reviews, even when small scratches appear during operation, the coating does not come off. In addition, the product is completely smooth, as if it had not been subjected to any impact. The only disadvantage of this burnishing can be called the fact that it takes a rather long time and requires constant contact with the product (it is necessary to turn the knife up to 4-6 times a day), as otherwise it will cause pie blotches on the surface of the knife.

Acetic acid

Burning a knife in vinegar is practically no different from the two previous methods. The knife must also be placed in vinegar and periodically shaken and turned over to prevent bubbles from settling on the surface of the product.

In addition, if the knife handle is plastic or plastic, then it must be protected from vinegar, for example, covered with paraffin.

The knife can also be burned in heated vinegar, then this method will be more similar not to blackening, but to metal etching.

The knife can not be completely lowered into the vinegar, but the blade can be wrapped in a fleecy cloth well saturated with vinegar, but this method is more time-consuming, as the fabric needs to be periodically moistened.

The coating is pretty beautiful, not quite black, but rather, dark gray. Such a burnishing of the knife is not particularly strong, so it is best to use it for decorative knives and other metal interior items.

It should also be said that it is not any metal that can be blackened with vinegar, but only hydrocarbon. Therefore, first watch carefully how the steel behaves. If you notice that white blotches appear on the surface, then this method of burnishing, unfortunately, is not suitable for this metal, later blotches will not disappear, but will only become more contrasting.

Rusty varnish

Burnishing a knife with rusty varnish has both its advantages and disadvantages. The main advantage of this method is that you can burn knives that have tin solder, since all the previous methods are not suitable for these purposes - the tin will either dissolve or not change its color. In addition, with the help of rusty varnish it is possible to carry out spot burnishing of the knife, that is, to burn only certain areas of the blade or handle. The coating layer is rather thick compared to the previous methods, and the steel itself is dull after such a burnishing.

The disadvantages of knife burnishing in this way are that knives, especially industrial ones, are most often made of various alloys, and rusty varnish is very sensitive to impurities, that is, each metal in the alloy will be painted in its own color and red-brown and brown spots. If during the application of varnish you notice such an effect, it is necessary to remove the varnish as soon as possible, before oiling the surface, otherwise these spots will not come out and the knife will be damaged.

Other significant disadvantages include the fact that this method of knife burnishing is sensitive to various nuances of the process: degreasing quality, drying temperature, and burnishing time. In addition, the burnishing process is quite lengthy and requires your direct presence, since the varnish must be applied several times and every time after drying it is boiled for a couple, then rinsed under running water. All of these procedures must be repeated until you are satisfied with the end result. After that, it is necessary to place the knife in boiling oil for 5 minutes, and then wait for it to cool completely and only after that begin the process of grinding with a soft flannel cloth.

In addition to the above, at home and use the methods of burnishing a knife using calcination. Before burying the knife in this way, it must be coated with linseed oil, animal fat or wax. After that, the knife must be well calcined on fire. Some do this in an ordinary kitchen pan, but keep in mind that the dishes will be spoiled after that.

Before using this method, you can pre-immerse the knife in a solution of copper sulfate and ammonia: 100 grams of vitriol and 10 grams of ammonia are diluted in one liter of pure distilled or settled water. Immersion and burning of the knife must be done several times until you get the desired color of the metal.

Chemical burnishing

Burning a knife in this way can only be carried out under conditions of good drawing and ventilation, as otherwise it can be hazardous to health!

In a mixture of saltpeter and caustic soda (30 grams of nitrate and 100 grams of soda) heated to 140 - 160 degrees, place the knife and keep it there for at least half an hour. With this method of burnishing, a beautiful deep black is obtained that gives a blue color.
In an alkaline solution, dilute potassium or sodium hydroxide in a high concentration and place a knife in this solution. This method will give a bluish film on the surface of the knife.

Oiling

Coat the knife with oil - you can use flaxseed, machine, weapons, even sunflower. You can apply oil either with a brush or simply by dipping a knife into it. After that, bake the knife in the oven to 400 degrees. After cooling, check the result and if the color is not saturated enough, repeat the procedure. When finished, cool the knife and remove the oil with a soft flannel cloth.

Conclusion

As you can see, the methods of metal burnishing at home are quite diverse. The only difficulty may be that you never know how a particular metal will behave when using a specific burnishing method. But most coatings can still be removed from the surface of the metal, which means the object in any case will not be damaged forever.

Which of the above methods to use is up to you to decide, but they all deserve attention and allow you to achieve good results.

Burnishing is the process of producing an oxide layer a few microns thick. It is also called oxidation, blackening or blueing. This is a dark, almost black coating, but there are other shades.
Basically, burnishing is used as a decorative coating, but initially, in the first place, it is intended to protect steel from corrosion.

I will show you a way to make a simple blunt knife at home, using all available components.
What do you need?

- Boiling water 0.5 liters;
- Citric acid 50 grams (can be bought at any grocery store).

The proportions are approximate, therefore, strictly following them is not necessary. It all depends on the volume of dishes in which you will etch your blade. You need to know that increasing the concentration of citric acid accelerates the oxidation process, but at very high concentrations it can lead to uneven coverage.

Knife Burning Process

We take glassware, according to the size of the knife blade, so that it can be completely immersed in the solution.
We boil water in a kettle. Then we take and carefully pour boiling water into a jar. Here you have to be careful, as the jar may burst. To prevent this from happening, you can first pour a little boiling water at the bottom and let the jar warm up, then add the rest.

Next, pour citric acid into the water and mix thoroughly until completely dissolved.
Before immersing the blade in the solution, it is advisable to wipe it with alcohol to remove all excess grease and dirt.
Immerse the blade of the knife.

After 1-2 minutes, a reaction will begin, which will be noticeable in numerous bubbles.

Burnishing will take approximately 30 to 60 minutes. Everything again depends on your requirement for the color of the coating and the grade of steel of the knife.
The following must be done during the entire burnishing process:

- Every 10 minutes, remove the knife and wipe the blade with a soft paper or cloth, removing black deposits from the surface.
- Approximately every 1-2 minutes, it is necessary to move the blade in the solution, thereby dropping large gas bubbles from the blade. This will ensure uniform coverage.

After a period of time, if you are satisfied with the color of the coating, you need to wipe the blade with sunflower oil for the last time. This will stop the reaction, make the coating uniform and strong.
On this, the blade bluing is completed.

In the end I want to add:
- Do not inhale the pores of gases during burnishing, as they are harmful. And better use ventilation if you have one, or at least open a window in the room.
- For a stable process, the water must be hot. Burnishing does not go in cold water. Boiling water is not necessary, but 80 degrees Celsius should be.

If you get small stains - do not worry, they will leave after the first or second operation.
Such a coating is quite resistant and will last more than one year.

piersonlitsee1990.blogspot.com

Source: https://sk-arsenal.ru/en/kak-zachernit-lezvie-nozha-v-domashnih-usloviyah-sposoby-i-tehnologiya-voroneniya.html