Basic knowledge of metal commemorative coins
Under normal circumstances, gold is more resistant to corrosion than silver; silver is more resistant to corrosion than copper; metals such as zinc, aluminum and iron are more susceptible to corrosion. For alloys, sometimes depending on the chemically active metal, such as pure gold, the stability is better, and when copper is added to the gold to form an alloy, black spots tend to appear on the coins.
But brass (copper-zinc alloy) is more resistant to corrosion in the atmosphere than pure copper. Polyvinyl chloride is harmful to coins in packaging materials. Water vapor, sulfide and carbon dioxide in the air are also very harmful to coins. For example, sulfur reacts with silver to form silver sulfide, which makes the surface of silver coins gray and black. The moisture in the air also accelerates the oxidation process of the coin. During the appreciation process, the bare coin is touched by hand, so that the sweat marks leave a fingerprint on the coin, and the dust in the saliva and the air falls on the coin, and these additions will accelerate the corrosion process of the coin.
Choosing the packaging method is the basic skill of the coin collector. In general, the optional packaging is a plastic box that is not a polyvinyl chloride, a paper center with a polyester film round hole, a polyester film bag, a paper bag, and the like. Optional materials are polyethylene, polypropylene, and polyester film. In order to facilitate appreciation, it can also be placed in the collection book on the basis of transparent packaging. The key point is that PVC-containing materials cannot be used to package and store coins. The harm cannot be underestimated. In order to isolate the air, there are generally two methods of airtight and vacuum encapsulation.
Airtight means to isolate the air but not to clean the air inside the package. The vacuum encapsulation places the packaging material in close contact with the surface of the coin, which can also damage the coin. The easiest way to isolate the air is to soak the coin in absolute alcohol. The disadvantage of this method is that it is not easy to watch, but the effect is better. It is generally not advisable to directly touch bare coins, especially if you do not touch refined coins, uncirculated coins (UNC) or high-end coins. The place where the hand touched the coin must be the place where the corrosion first turns black. If you really want to take a coin, use a clean soft paper or cloth to separate the edges of the coin.
Metal commemorative coins generally do not need to be cleaned. In case of soiling, just wash them in warm soapy water, then rinse them with water and put them in two soft cloths to absorb the water. If the silver coin with high silver content is only slightly oxidized, it is best to use ammonia solution with sodium carbonate solution and toothpaste to prepare a paste to clean, or use white vinegar with a small amount of water, soak the silver coin in its solution for a few minutes. Gently wipe the surface with a cotton ball dampening solution. After the surface oxide layer is dissolved, rinse it off with water.
Metal commemorative coin cleaning notes:
First, you cannot use concentrated sulfuric acid or nitricacid solution;
Second, it cannot be brushed with a toothbrush or sandpaper;
The third is to wash the residual decontamination solution and dry the coins. It is a pity that you should not clean the gold and silver coins easily. If you need to clean it, it is best to ask the professionals of the coinage or distribution agency to take care of it.
But brass (copper-zinc alloy) is more resistant to corrosion in the atmosphere than pure copper. Polyvinyl chloride is harmful to coins in packaging materials. Water vapor, sulfide and carbon dioxide in the air are also very harmful to coins. For example, sulfur reacts with silver to form silver sulfide, which makes the surface of silver coins gray and black. The moisture in the air also accelerates the oxidation process of the coin. During the appreciation process, the bare coin is touched by hand, so that the sweat marks leave a fingerprint on the coin, and the dust in the saliva and the air falls on the coin, and these additions will accelerate the corrosion process of the coin.
Choosing the packaging method is the basic skill of the coin collector. In general, the optional packaging is a plastic box that is not a polyvinyl chloride, a paper center with a polyester film round hole, a polyester film bag, a paper bag, and the like. Optional materials are polyethylene, polypropylene, and polyester film. In order to facilitate appreciation, it can also be placed in the collection book on the basis of transparent packaging. The key point is that PVC-containing materials cannot be used to package and store coins. The harm cannot be underestimated. In order to isolate the air, there are generally two methods of airtight and vacuum encapsulation.
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| 4cm Metal Historical Medal Customization |
Metal commemorative coins generally do not need to be cleaned. In case of soiling, just wash them in warm soapy water, then rinse them with water and put them in two soft cloths to absorb the water. If the silver coin with high silver content is only slightly oxidized, it is best to use ammonia solution with sodium carbonate solution and toothpaste to prepare a paste to clean, or use white vinegar with a small amount of water, soak the silver coin in its solution for a few minutes. Gently wipe the surface with a cotton ball dampening solution. After the surface oxide layer is dissolved, rinse it off with water.
Metal commemorative coin cleaning notes:
First, you cannot use concentrated sulfuric acid or nitricacid solution;
Second, it cannot be brushed with a toothbrush or sandpaper;
The third is to wash the residual decontamination solution and dry the coins. It is a pity that you should not clean the gold and silver coins easily. If you need to clean it, it is best to ask the professionals of the coinage or distribution agency to take care of it.
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