Silver, white, with strong plasticity, is easily eroded by some harmful substances in the atmosphere, making the color dim. For example, under certain conditions, sulfur-containing substances, oxides, concentrated ammonia water, etc. It may react with ancient silverware, producing dark gray Ag2S and AgCI precipitates, or water-soluble Ag(NH3) complex ions, thus causing silverware to be dissolved and corroded. In addition, ancient silverware is often a kind of silver-copper alloy, which comes into contact with corrosive media.
Electrochemical corrosion will occur and silverware will change color.
Silverware is also easily corroded by oxides, forming horn silver (silver chloride), which is gray or brownish purple. If only a layer of silver chloride film is formed, it will present a pleasing antique tone and will be dyed with various colors. These ancient spots are stable, which increases the artistic charm of the artifacts and should be preserved. When the silverware is not seriously rusted, don't handle it easily, because it is not beautiful but stable. Only when it is determined that the appearance can be improved and the pattern can be clarified can the treatment be carried out. If the color is too dark, you can dip a soft cloth into a paste made of chalk powder and water, or wipe it with alcohol containing a few drops of ammonia water. You can also use electrochemical reduction method to put the utensils and lead together, soak them in 5% sodium carbonate solution or sodium hydroxide overnight until the stains disappear, immediately wash them with distilled water, and then polish them with soft cloth or cotton balls. The dark color of sulfide can also be eliminated by diluted sodium thiosulfate solution. When sulfide corrosion is serious, the silverware metal body no longer exists and cannot be reduced, so it can only be cleaned and dried, and the soil rust on the surface can be softened and removed with 20% glacial acetic acid.
Some silverware containing copper may produce a black surface of copper oxide when heated. This oxide stain can be removed with 5% sulfuric acid solution. The details can be shaped according to the local shape of the silverware, with a mold made of wood or tin as the cushion, and the top lined with soft cowhide or wool felt, which can be restored by pressing with a vise or hammer. In the process of shaping, it is necessary to minimize hammering, especially to avoid hitting with hard hammers and hard anvil, so as to prevent the expansion and deformation of the blank and increase the difficulty of shaping.
If the texture of some silverware is well preserved, it can be heated and boiled in alum water as needed, and then sealed with trimethyl Bo Tu film.
The maintenance of silverware can also use XD- 1 silverware protectant. Its outstanding advantage is that the surface of silverware is covered with a thin and uniform protective film. The film has strong adhesion, no corrosion to silverware and reversibility. Another method is to treat the discolored silverware with benzotriazole (PMTA) formic acid solution, which has good rust removal effect and no damage to silverware.
Attention should be paid to the preservation of silverware: the house where silverware is stored must be kept clean, free from dust and air pollution, and there should be no pollution sources near the house. It is particularly important that there should be no substances such as hydrogen sulfide, sulfurous acid gas and strontium hydroxide, so as not to make the silverware dull. Dust removal and cleaning can be wiped with a soft cloth. Cloth can be dipped in a paste made of chalk powder and water, or wiped with alcohol containing a few drops of ammonia water. Dust on large items can be removed with a vacuum cleaner or a hair dryer. Protect silverware from mechanical damage. It should be placed in a dust-proof glass cabinet when it is displayed and in a brocade box when it is kept.