1. Why do silver ornaments change color?
Silver ornaments and silver handicrafts often change color over time.
The laws of nature tell us that any substance will become unstable at high energy after absorbing energy, which is scientifically called "thermodynamic instability". Therefore, the metal will naturally release energy and try to return to the original extremely stable ore state. For example, silver is metallic silver obtained by heating argentite (Ag2S) at high temperature. On the one hand, its performance is very unstable due to the increase of its own energy. Another important factor is the great affinity between silver and sulfur. Scientists have determined that when silver meets hydrogen sulfide gas or sulfur ions in the air, it is easy to form an extremely insoluble silver salt (ag2S) (silver salt is the main component of argentite). The amount of this chemical change is very small. As long as silver meets hydrogen sulfide gas or sulfur ions in the air, the following chemical reactions will occur:
4ag2H2SO2=2ag2S (black product) 2H2O
As a result of the reaction, silver sulfide is produced on the surface of silver. Because silver sulfide is gray-black, with the intensification of the reaction, silver sulfide increases and thickens, and the surface color of silver gradually turns from white to yellow to gray, and finally turns black.
And where did the silver sulfide come from? It is a natural product. First of all, human and animal feces will produce a lot of hydrogen sulfide after bacterial decomposition, and protein in plants will also produce hydrogen sulfide after corruption; In addition, human sweat also contains sulfur, and contact with silver products will make silver discolor, especially the hydrogen sulfide produced by sewage and garbage discharge in urban air is even more amazing, so it is not surprising that silver discolors.
Second, the maintenance of antique silver jewelry
Antique silver ornaments are historical relics that people collect, appreciate or use for a long time. Antique and original, it can not only make people taste the charm of ancient culture, but also make people dating correctly. The principle of antique silver jewelry maintenance is to protect the original flavor of the object as much as possible.
1. Surface maintenance: If the surface of ancient silver jewelry is only gray or brown patina, it is a relatively stable Ginko chloride spot color, which is the deposition of scenery and can enhance the artistic charm of the objects. This ancient scenic spot should be well protected, not treated. For objects with particularly dark colors and unclear patterns, only when it is certain that the surface of the instrument will not be damaged and the pattern will be clear can they be treated. You can drop a few drops of ammonia in alcohol and then gently wipe it with a soft cloth or cotton. When wiping, enough is enough. Don't rub it too bright, and you can't wash it with silver, otherwise you will lose the ancient spots formed by the long pattern. For objects with particularly serious corrosion, lightly brush them with a soft brush dipped in dilute hydrochloric acid until the rust disappears, immediately rinse them with distilled water and dry them with a soft cloth.
2. Overall maintenance: When storing silver jewelry, avoid being squeezed by heavy objects to avoid collision, deformation or wear. For antique silver ornaments that need to be trimmed, broken silver ornaments should be bonded and welded with broken silver ornaments. The deformer can use tin or wood tough materials to line the local shape of the object with soft cowhide or wool felt, and then use pliers or hammers to restore the original appearance as much as possible.
The room where silver ornaments are stored must be kept clean, dust-free and pollution-free, without hydrogen sulfide and sulfurous acid gas, so as to avoid the silver ornaments from darkening. Put it in a glass cabinet when it is displayed and in a brocade box when it is kept. You can also classify the ancient silver ornaments collected on the velvet, so that the whole set of objects will not be lost and confused, and it is also convenient to appreciate. When folding and storing, put a layer of cotton cloth on the watch to avoid scratches.
Third, the maintenance of modern silver jewelry
1. Appearance maintenance: Modern silver jewelry is an object that people often use and wear for a short time, which requires beauty, generosity and silver. The best maintenance method is to wear it every day, because the grease of healthy people can keep silver jewelry from being oxidized, keep it moist and smooth, and the more you wear it, the brighter it will be. Second, try to avoid contact with chemicals and seawater to avoid discoloration. Wipe it with cotton cloth after wearing it and keep it in a jewelry box or bag.
For silver ornaments that have been oxidized and discolored, you can brush them with a fine brush dipped in toothpaste, dry them with cotton cloth, and then wipe them with silver cloth to restore their original luster. Try not to use silver washing water, because silver washing water is corrosive to silver, and it will turn yellow more easily after washing with silver.
More exquisite three-dimensional silver jewelry, don't rub it too brightly, which will affect the three-dimensional effect. Silver can't be put together with other metals (especially gold), otherwise it will be assimilated after a long time, that is, silver jewelry watches will have other metal colors, which will affect the appearance.
2. Maintenance of inner surface: The maintenance of modern silver jewelry can refer to the maintenance methods of ancient silver jewelry. Slightly different, for modern silver jewelry that is particularly damaged, it can be destroyed and recast to achieve beautiful results. Antique silver ornaments with particularly serious operation cannot be recast, so they can only be preserved as much as possible to avoid regret.