Noble patina

Copper and bronze objects in humid air are gradually covered with green bloom; Ancient candlesticks and door handles, mantel clocks and bronze statues in the squares turn green and dark. The plaque formed on them is the so-called noble patina, or antique patina, as it is also called. Noble patina is very appreciated by art lovers. Let's learn how to use a rapid method to quickly obtain a noble patina.

Noble patina is very appreciated by art lovers

In order to form a noble patina, the long-term, for many years, exposure to air containing moisture and carbon dioxide (carbon dioxide) is necessary. In the presence of these two substances, a film of basic copper carbonate is formed, similar in composition to the well-known malachite mineral. We will not succeed in obtaining artificially mineral - it is impossible to reproduce its dense crystalline structure. But the creation of a noble patina will take us not years, but a few minutes, well, as a last resort, an hour or two.

To a small copper object (and for approximate experience it is even better - to a plate or a piece of copper foil) attach the wiring with the stripped ends. Wipe the surface, as you did more than once, with fine sandpaper, put the object in a hot solution of washing soda, rinse with water and immerse it in a weak solution of vinegar - this will help avoid premature oxidation.

In the meantime, prepare the electrolyte: two teaspoons of ammonium chloride (ammonia) in a glass of water. Without touching the copper object with your hands, remove it with tweezers (or posting) from the vinegar solution, rinse it under the tap and lower it in the solution of ammonia. Connect the wiring to the positive pole of the battery, and connect its negative pole to the copper electrode - to any copper plate that you can not clean so carefully. Soon the cathode, i.e., the object on which we are applying the noble patina, will be covered with a red matte layer. But, there must be a green layer, which we counted on!

We will not, however, hurry. Ten minutes later, remove the object without touching it with your hands, and place it so that water runs off it, but the surface is not scratched; You can hang it for posting. It will take some time, and the red layer will turn green. This is a red patina on copper turned into a green, similar to malachite.

An even greater effect can be achieved if an electrolyte solution of ammonia with a concentration of about 25% is taken, but in this case it is necessary to work under the strain or in fresh air, since the concentrated ammonia solution has a very strong odor. Suspend the item so that part of it is above the electrolyte. Then the part that is in the solution will remain red, and the part that is in the air will be covered in an hour with a small green-blue film, very similar to a real noble patina.

No need to hurry, putting this experience, and increase the current: the slower the process, the stronger the layer of basic carbonate of copper. But still, the clock is not years, and the strength of our film is far from the natural patina (although the artificially noble patina obtained is no less beautiful). To preserve it, cover the green cover with some colorless varnish.