KNIFE BLUING IN CITRIC ACID

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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.