Copper rust is generally divided into harmless rust and harmful rust. Due to the erosion of water, soil and atmosphere, the surface of bronzes has gradually changed, and they have formed a protective layer on the surface of bronzes to prevent them from being corroded again, adding a quaint color to bronzes. This is commonly known as "harmless rust". Harmful bronze rust is as harmful as green powder, commonly known as "bronze disease", that is, harmful rust. The development of harmful rust will make the loss of utensils gradually serious and spread continuously. This phenomenon must be dealt with in time and stored in isolation.

The rust layer of ancient bronzes is extremely complex, with many layers. Some rust covers up the decorative patterns or inscriptions of bronzes, and even makes the objects deform and lose their original appearance. Therefore, removing these harmful rust is one of the important tasks for the protection and treatment of bronzes. In the past, the method of rust removal for bronzes was hammering with carving knives and chisels. Remove rust. When hammering, the position should be accurate and the strength should be appropriate. Although this method is simple, it is easy to damage the original, especially the inscriptions and ornamentation, so it must be carefully removed and brushed clean. Some rust layers are very hard and difficult to remove. You can use sludge to make a long strip, surround the rust, drop the solution with a dropper to soften and decompose the rust, then dig it with a knife and rinse it with water. It should be noted that sometimes it is not necessary to adopt a comprehensive rust removal method, but only some local treatment is needed.

"Rust" is the key to bronze ware identification.

It is very important to know the corrosion characteristics of ancient bronzes in identification. Due to different regions, different bronze materials in different periods and different corrosion ages, it will all be manifested in copper rust. We usually say erythema, green rust, black paint, mercury oozing, etc. It is the most common phenomenon of copper rust.

In fact, there are many rust colors besides this. True rust is born in bronze ware, which has a foundation, layers, hardness, fastness and luster. There are two main methods to make fake rust, one is short-time corrosion, and the other is daubing and pasting. Therefore, rust is mostly superficial, green in color, not hard, easy to fall off, or wet and sticky. After a long time, surface cracking will occur. This kind of situation sometimes catches fire and has a pungent smell. It is very important to observe the corrosion of bronze surface. Many imitators with poor level can basically find rust characteristics. Therefore, counterfeiters also strive to study the method of making fake rust after imitation casting. Around 2000, someone asked me how to eliminate the residual odor after chemical corrosion. Before this, a part of fake rust can be found by smelling it, and then the smell is gone, which shows that the manufacturer of fake rust has solved this technical problem. Judging from the current counterfeiters, counterfeiting rust is still a difficult point. As long as careful comparison is made, there are always clues in various methods of making fake rust. The identification of rust cannot be fully expressed in words. It is a comparative appraisal to look at the real thing and observe different kinds of rust.

There is also a forgery method, which is patchwork. About ten years ago, I saw a bronze horse. Han dynasty style, there is a piece of Han dynasty bronze on the horse's chest and hip, and the rust is thin and hard. In addition, about four-fifths of the area is covered with rust, and there are traces of artificial smearing. The owner also saw it, but he thought the vague part was caused by maintenance. I looked at the horse's head carefully, and there was no trace of repair. The rust on the horse's head was different from that on the chest and buttocks. Finally, I came to the conclusion that all horses are imitations. The counterfeiter's method is: first cast a bronze horse, then dig out the part of the chest and buttocks of the bronze horse that is less than one-fifth of the total area, make up the two copper pots in the Han Dynasty, and skillfully use the original radian of the copper pots to cover up the fake rust after welding. Therefore, when we find that there are two different characteristics of rust on the whole equipment, we should pay attention to it. If the whole equipment is real and only partially repaired, it should be treated as genuine equipment maintenance. It is not uncommon to encounter restored bronzes in the collection. If you should have looked and didn't find it, the price difference would be big.