From lovers of antiques, you can often hear a word like “patina”. What it is, many Internet users would probably like to know. Below in the article we will try to give the most detailed answer to this question. So what is patina?
Definition of a concept
Everyone who has ever visited the museum must have seen greenish old coins that darkened over time with candelabra, sconces, etc. The plaque covering these metal objects is called patina. The color of such a film can vary widely. Most often, the patina formed under the influence of atmospheric factors during natural aging has a greenish tint. But sometimes it is brown, dark gray or bluish.
Chemical formula
The answer to the question: "Patina - what is it?" from the point of view of a chemist is very simple. The film formed on copper is nothing like ordinary CuCO 3 . This may be, for example, Cu 2 (CO 3 ) (OH) 2 or Cu 3 (CO 3 ) 2 (OH). The plaque of the first variety has greenish tones (malachite), the second - bluish (azurite).
Natural patination usually occurs over a fairly long time. Most often, a film of a substance such as copper carbonate on products, depending on conditions, is formed within 5-25 years. If the item is in a humid environment, oxidation, of course, will go faster. In a dry room, the coating will be covered later, respectively.
Initially, the concept of “patina” (what you now know) was applied only to the film formed on copper, bronze or brass. Later, the same word began to be called the plaque that appears on wood, gypsum, a bluish tint on blued steel, etc.
Patination History
Everyone knows that antique things look solid and prestigious. The reason for this is usually copper carbonate - patina. Since it takes a very long time to wait until this noble plaque appears on the surface of a product, various techniques have been developed that allow it to be obtained artificially.
The first hand-made old things began to be made in the 14th century in Florence. For patination, gypsum was then used, which filled the voids on the surface of wooden products. After drying the alabaster mixture, gold foil was glued onto the product . Then everything was varnished.
The technology of artificial patination of metals has also been developed quite a long time ago. Ancient masters noticed that the plaque formed by burning fat on metal utensils delays its rusting. Therefore, approximately the same chemical composition of the film began to be applied to sculptures and other art castings.
Where is patination used?
Today, this technique also most often decorates furniture designed for residential premises. Sometimes patination is used to artificially age decor items in the offices of business people. Forged products finished in this way look very impressive. Patination can be decorated with metal railings of stairs, fences, parapets of balconies, etc.
Also very often this technique is used to artificially age copper and brass coinage. As in the past, patination can sometimes be seen on cast metal (steel, bronze and cast iron) decor items. It happens that souvenir "old" coins, medals, coats of arms, etc. are made in this way. Very often, an artificial patina covers copper chandeliers, sconces, decorative plates for sockets, etc.
Artificial Patina: Aging Paint
For patinating furniture, panels, metal gratings , etc., this very gentle technique is very often used. Aging is carried out as follows:
A metal or wood product is thoroughly cleaned and degreased.
Its surface is polished, and sometimes slightly bleached.
The actual patination is performed. In this case, acrylic paints are usually used. Such compositions are resistant to adverse environmental influences and are inexpensive. For the design of small products, other more expensive dyes can be used.
Surface grinding is in progress. In this case, the protruding relief details are highlighted, and the recesses remain dark. As a result, a “patina” coating is uneven in tone.
The product is covered with a protective layer of varnish or oil (for wood).
Aging of forged, hammered and cast products by chemical means
Reagent patination is often used in the manufacture of decorative metal products. In order to get a noble film on such things as coinage, sculptures, gratings, etc., a variety of chemicals can be used. It is very difficult to make a natural green coating on copper, bronze and brass objects. But you can get a patina of other interesting colors. For example, sometimes the processing of copper products is carried out with the following composition:
sulfuric liver - 2-3 g;
table salt - 2-3 g;
water - 1 liter.
Upon contact of copper products with the resulting solution, a light patina of a pleasant gray shade appears on them.
For the artificial aging of brass decor items, the following composition is often used:
By mixing these ingredients, a violent reaction begins. The color of the patina in this case is almost black. Masters try to use such a solution as quickly as possible (maximum within 20 minutes). Otherwise, it loses its properties and becomes unsuitable for patination.
As you can see, chemicals that are quite dangerous to human health are often used to age metal decor items with the chemical method. Therefore, such patination is done only with gloves and with open windows.
Where is thermal patination used?
This technology is often used to make beautiful steel products. For example, by a very simple technique, burnishing is performed. The metal is placed on fire and held there until redness. Then it is very quickly dipped into a container with engine oil. As a result, a black patina coating almost instantly forms on the steel surface.
In this way, an artificial “patina” is applied to metal and wooden surfaces. What is it we have found out. By and large, a natural patina is a physical reflection of decades, centuries, and sometimes millennia, that have passed since the product was manufactured. All kinds of artificial aging technologies are used to a large extent for the manufacture of all kinds of decorative products that can make the interior of a residential building solid and prestigious.