How to maintain the ancient coins in the pit?

Ancient coins with different materials have different maintenance methods:

1. Maintenance of ancient currency

Talking about the Rust Removal of Metal Coins Generally, the rust color on copper coins should be kept as original as possible, because most of them are harmless rust. However, when the ancient coins are rusted into pieces, the coins are unrecognizable or have harmful rust, it is sometimes necessary to remove rust.

Soil rust is generally a mixture of soil and calcium and magnesium salts or a mixture of soil and copper rust. Before treatment, gently brush off the dirt on the ancient coins with a soft brush dipped in water, and then immerse them in glacial acetic acid diluent (glacial acetic acid is a colorless and transparent acidic chemical solvent, originally used in photographic darkrooms). After an hour, touch the old money with a stick until it is scattered. Then put on rubber gloves, hold an ancient coin in one hand and gently scrub it with a brush in the other. There is no need to wipe off the bronze rust on the back of ancient coins without inscriptions and marks, so as to maintain some characteristics of unearthed ancient coins. After rust removal, rinse off glacial acetic acid solution with clear water, absorb water with a soft towel or cloth, and finally lay it flat on clean paper to dry.

In the absence of conditions, rust can also be removed by soaking in vinegar. This rust removal method takes about one day and one night to barely dissolve the rust, which is extremely inefficient.

For powdery rust that cannot be removed by soaking, sludge can be used to wrap the rust removal part, concentrated acetic acid can be dripped into the dropper to decompose the rust, and the rust can be removed by gently removing the rust with the needle tip, scrubbing with water and neutralizing with ammonia hydroxide.

Fetal hair rust is the rust layer of ancient money corroded from the inside out. In this case, the money body becomes thicker, and most of them are sealed and kept without rust removal.

Generally, gold and silver do not need rust removal. In a few cases, when rust removal is really necessary, it can be soaked in 15% glacial acetic acid solution or 10% sulfuric acid solution. If fetal hair rust is found on gold and silver coins, you can use a brush dipped in 5% trimethyl resin to coat the second and third layers, which will play a sealing role.

There are many ways to remove rust. If the rust is light, it can be properly heated and peeled off by using the principle of thermal expansion and cold contraction. Glacial acetic acid soaking method and heating method can not be used for iron money with serious corrosion. For iron coins that need special rust removal, zinc caustic soda electrochemical reduction method and caustic soda solution electrolysis method can be used. Hydrogen furnace reduction method can be used for more expensive iron money.

2. The storage of ancient money

Rare metal coins were once decorated in ivory boxes and bone boxes. According to the current conditions, it can be put into a plexiglass round box and filled with nitrogen for preservation.

If possible, gold and silver coins can be put in boxes or safes.

Ordinary metal coins are matched by age and edition, and put into boxes in order. The wooden box is 60 cm long, 40 cm wide and 8 cm high, with a thin layer of foam nailed to the bottom. The old money is back, to protect Qian Wen and to check the registration number. Ancient money was fixed around with a few pins. There are also holes around the ancient coins on the cardboard, which are fixed with wires. There are three layers of cardboard stuck together, and the top layer is carved into a round hole according to the size of ancient money. Put the ancient money in and cover it with plastic film.

If you have a large collection of ancient coins, you can also register them for easy preservation and reference. The contents of registration include registration number, name of ancient coins, texture, weight, diameter or size of coins, grade, current situation, source, and explanation, and then rubbings and photos are attached.

The surface of coins in collectors' hands always leaves traces due to age and circulation, such as metal blackening, corrosion spots, dirt and so on. It is natural that some collectors want to clean these coins and restore their lost luster. Unfortunately, there is no way to completely restore the quality of old coins. Moreover, in the absence of knowledge and experience of coins, cleaning itself will often bring damage to coins, eventually destroying their appearance, making it impossible to recover by any method. In order to determine which coins need to be cleaned and how to clean them so that coins can get above average quality, some experience is needed. Before you start cleaning up your collection, you'd better do some experiments with coins that are not used for collection. Only after gaining some experience can we clean unsatisfactory coins and obtain relatively satisfactory results.

1, gold coin cleaning method

Gold coins don't really need cleaning. If it is dirty, wash it with warm soapy water, then rinse it with clear water and put it in two soft cloths to absorb water. In any case, no rubbing action is allowed when cleaning or absorbing water. Even soft cloth will leave tiny scratches on the polished coin surface.

2. Cleaning method of silver coins

The cleaning method of silver coins first depends on the oxidation degree and color of silver coins. The oxides formed on the surface of silver alloy with high silver content have different characteristics from those formed on the surface of silver alloy with low silver content.

If a coin with high silver content is left underground for a long time or influenced by other unfavorable factors, a thick layer of oxide will be formed on its surface. At this time, the coin should be soaked in ammonia solution 1 hour (composition: 90% water, 10% concentrated ammonia water). If there is no ammonia solution, sodium carbonate solution can be prepared instead (30g of edible soda ash is dissolved in100g of water). Put the coin in the solution for several hours until the oxide is completely dissolved.

If the silver coins with high silver content are only slightly oxidized, it is best to make them into paste with ammonia solution, sodium carbonate solution and toothpaste for cleaning. This paste should be soft to the touch and contain no fine hard particles. The method is to gently smear it on the surface of the coin with a finger or a soft brush, and rinse it with clear water after the oxide is dissolved.

Silver coins with low silver content and copper as the master alloy will turn green when severely oxidized. Clean this coin, preferably with 5% dilute sulfuric acid solution. When the green rust layer dissolves and recedes, the silver coins with high silver content are washed again. But if the oxide on the surface of the silver coin is uniform, there is no need to clean it now.

3. Cleaning method of brass coins

Time often leaves a layer of oxide on the surface of copper coins, which is brown, dark green or black depending on the environment and age. If the oxide is uniform and the metal is not corroded, then it is best not to clean it. Because the uniform oxide layer makes the copper coin have an appearance commensurate with its release date, it can also make the copper coin not easy to be corroded. For copper coins with uniform oxide layer, the only thing you can do is to wash them with warm soap to remove grease and sweat stains. Do not scrub hard when cleaning to avoid damaging the oxide layer.

It is best to use a slow reaction solution (such as 5% dilute sulfuric acid solution) to clean the oxidized coins, which can gradually wash away the corroded and damaged coin surface and keep the intact parts from being damaged. The soaking time of coins in solution mainly depends on the surface state of coins, that is, the degree of oxidation. The deeper and thicker the oxide layer, the longer the soaking time should be. Seriously oxidized coins can be soaked in the solution for several days and nights, while slightly oxidized coins only need to be soaked for several hours. In the soaking process, the dissolved oxide can also be washed with a soft cloth in warm water flow, so that the solution can better act on the newly exposed corrosion layer. Remember when cleaning: wear rubber gloves, hold coins with tweezers and clean them in the solution.

The quality of coins can be improved after cleaning, but psychological preparation should be made for corrosion pits and scratches exposed after cleaning. You can't make a decision until you have experience: is the coin worth cleaning? Will cleaning damage coins? And after the coin is cleaned, will the tiny part of the coin pattern be washed away with the oxide?

4. Cleaning method of bronze coins

The cleaning method of bronze coins is the same as that of brass coins. It is easier to restore the luster of the coin by applying a little toothpaste on the surface of the coin in advance and washing it with warm water.

Do not use strong sulfuric acid or nitric acid solution to clean copper coins and silver coins. This solution will also destroy the coin itself, especially the subtle parts of the coin pattern, and wash away the oxides at the same time.

If copper coins and copper-nickel alloy coins are seriously corroded (there is a uniform black, dark green oxide layer or thick black shell on the surface of coins), then they can be cleaned with concentrated sulfuric acid or nitric acid solution. Of course, this cleaning method is only for coins with no special value.

The cleaning process is as follows: pour nitric acid into glassware and prepare soda water. Put the coin into nitric acid solution with tweezers, and the oxide will dissolve quickly. As soon as the surface of the coin is wiped clean, pick it up with tweezers and put it in soda water. Then you can take out the coins by hand, rinse them carefully with warm water and dry them. It should be pointed out that nitric acid can remove oxides, and at the same time make the surface of coins potholes.

Washed copper coins look unnatural. Over time, copper coins will still turn black and oxide layers will reappear. But we still can't guarantee that the copper coin will generate a uniform new oxide layer and there will be no black spots on the coin surface. Therefore, it is best for the cleaned copper coins to naturally generate an antique oxide layer, giving people a sense of time.

The simplest way to make the coin naturally produce oxide layer is to soak the clean coin without grease in 10% sodium dithionite solution 10-20 seconds. Rinse and dry with a soft cloth. Copper coins immersed in dithionite solution will give off a pleasant bronze luster and generally will not be corroded again.

Coating varnish on the surface of coins is helpful to the preservation of copper coins and copper-nickel alloy coins. It is best to use glossy furniture varnish, which is easy to clean with acetone.

Before putting new coins (silver, copper, copper-nickel alloy and brass coins) into the collection box, please clean the places where your fingers have touched. We find that rust always begins where the hands touch.