Gold jewelry overview

Since the 1980s, there is a greater change in gold jewelry trends. The popular style has changed from a small and exquisite style to a bold and unconstrained style, showing a beauty of strength and strength.

Gold is the most popular jewelry metal, but price fluctuations have a great impact on its use. For example, when the “big” look and feel of jewellery fashion styles appears, it is precisely when the price of gold gradually rises. The use of hollow chains and electroforming technology allows gold jewellery to produce a more substantial appearance without having to add excessive weight.

The gold-colored alloys are once again popular. From the perspective of gold jewelry, the use of three-color gold (yellow, white and rose) is an important trend.

In the 1980s, American consumers had a great interest in gold with a high K number, which has been favored by Europeans and Asians since ancient times. The gold alloy with a high K number is also the main goal of the Americans, but it also has an interest in making 24K gold jewelry. In order to solve the problem of pure gold too soft, the World Gold Council sponsored the development of a new alloy 990 gold (1% titanium added to 99% gold).

Although most of the inlays in the jewelry market of the 1980s were cast, there are still some goldsmiths who use gold for handcrafting. The goldsmiths borrowed the jewel styles of the 1940s to wrinkle, pleat, and sculpt the fabric to mimic the fabric to obtain a woven appearance or to form a trim or mesh fabric. Through further exploration of the metal structure, after matt (grinding), brushing and polishing, a soft effect opposite to the polished gold is produced, and another way different from the polishing process is by weaving. The net, the "crack" and the crystallization make the modern artistic ornament produce a strong visual effect. In short, in addition to the mastery of technology, the processing of gold jewelry is more important to the pursuit of art.

With the vigorous development of the gold jewellery industry, the pattern style of jewellery is constantly increasing, and the composition changes are becoming more and more complicated.

Gold jewelry can be classified as follows according to the characteristics of the ingredients:

First, the classification of the composition of gold jewelry

(1) Divided into pure gold and K gold according to the color of jewelry

At present, there is no unified standard for the definition of purity in China. Although the draft national standards have been reviewed and approved, each region uses the traditional standards that it is used to (Table 1).

Table 1 Standard Classification of Gold Jewelry

Note: 1 "Name Method for Purity of Precious Metal Jewelry"

1. Pure gold: The author refers to pure gold, thousands of gold, and 24K gold as pure gold, that is, the amount of Au must be >990‰. However, in some areas, >22K gold is also called pure gold. Because this kind of gold is the same as 24K gold, it can only be used as a ring or necklace for wearing or collecting. Generally, it cannot be set with precious stones . This concept does not match the "pure" word, it is best not to use it.

2. K gold: A gold product with a unit of 4.16%, called K gold. The value of the constant 44.16% is 24K=100%Au, and 1K=4.16% is obtained. Since 4.16% is an infinite loop decimal, the value varies from place to place, so there are various K gold standards:

National Standard Draft, Shanghai Standard, Zhejiang Standard: 1K=4.1666%;

Customary use standards in Wuhan and other places: 1K = 4.15%;

Private K (old jewelry before liberation): <22K, 1K = 4.0%; >22K, 1K = 4.1%;

For 24K gold, it should theoretically contain 100% gold, but it is not uniform at home or abroad (Table 1). First, the value of 4.16% is different; the second is that the upper and lower limits of each 1K content are different. Mathematically speaking, the content between 23K and 100% is 24K, so it is not surprising that there is no uniformity.

When receiving old gold, pay special attention to the color of the "private K" gold.

Table 2 24K content standards around the world

(2) Divided according to the type of jewelry impurities

1. Clear gold-Au-Ag alloy;

2, bismuth gold - Au-Cu alloy, often containing silver . Cu<0.3% is called small gold, Cu>0.3% is called big gold;

3, gold titanium alloy - Au-990 ‰, Ti10 ‰, its color is close to pure gold, wear-resistant and durable, impact performance is close to K gold, is a new foreign product;

4, an aluminum alloy, gold -Au78%, Al22%, is currently developed in Japan in addition to black 18K gold, the gold jewelry this alloy be darkest, most red one.

According to a large number of electron probe analysis data, the main impurity components of pure gold are Ag, Cu, Fe, Ni, etc. The main alloy components of K gold are Ag, Cu, Zn, Ti, Al, etc., and also contain Sb, Sn. , Pb and other trace elements. It is this alloy composition and impurity elements that create a colorful gold self-decoration.

Second, the structural classification of gold jewelry

The so-called structure refers to the uniformity and combination of the parts of the whole piece of gold jewelry. According to its structural characteristics and process methods. Generally can be divided into two types: uniform gold and non-uniform gold:

(1) Uniform gold - such as various types of cast Tianyuan ring, flower ring and part of the set ring.

(2) Non-uniform gold - there are the following categories:

1. Gold plating: A thin layer of gold foil is plated on metal or alloy. Common metals (carcasses) are Ag, Cu, Ni, Cu-Zn alloys, Cu-Ti alloys, etc. Generally, metals or alloys similar in color to gold are used. Since Ni tends to adhere to gold ions, an adhesion layer is usually plated on the carcass and then gold plated.

For example, the results of electronic probe analysis of the belt imported from the United States sent by a bank in Guilin are shown in Table 3.

Table 3 Analysis results of an electronic probe for an imported chain in the United States

The thickness of gold plating is generally about 5μm. Some manufacturers often plate very thin for profit, only 1~3μm, but gold plating can also be as thick as 50μm. The so-called Italian gold and Japanese gold, which are sold in the market, are actually gold-plated products.

2. Gold: The gold foil is attached to other metal sheets (carcass), and the two are tightly combined by rolling. The carcass is Ag, Cu, Cu-Zn alloy or the like. The Ag tire is soft in texture and is not easy to open and peel off. The hardness of the latter is quite different, and it is easy to tear and take off.

The thickness of the gold is generally ten to 50 μm, and it is difficult to achieve a general process of thinner than 5 μm. The gold on the market is sometimes marked with (1/10) 18K, (1/20) 18K, etc., which means that the gold foil is 18K, and the ratio of the thickness of the gold foil to the thickness of the carcass is 1/10 or 1/20; in the United States, Gold is also called gold filling, commonly used 14KF or 18KF mark, which is different from 14K or 18K uniform gold.

3, welding gold: Where the gold jewelry welded by welding, temporarily called welding gold, such as the vast majority of necklaces, set treasure ring. Since the melting point of the flux is lower than that of the parent gold, the color formation is generally 10% to 20% lower than that of the parent gold. Therefore, when calculating the color, it is necessary to pay attention to the unevenness of color formation. For example, a necklace with a color of 99%, the flux gold generally accounts for 2% to 4% of the whole weight, the height is up to 6%, and it is set to 5%. When the flux is 90% Au, the mother gold color is At 99%, the color of the entire necklace should be:

99%-90%×5%=98.5%

4, combination gold: the different parts of the color into a gold jewelry. For example, for a pair of earplugs, the gold content of each part is: 99.72% of the ear leaf, 93.72% of the earplug, and 88.65% of the earplug; 5 strands of a strand are 24K gold, and 1 strand is 22K gold. Pay special attention to these structural features when it comes to color identification.

5, color gold: refers to a gold jewelry consists of a variety of ribbons. Each ribbon is the same color as the parent gold, but is tinted with a small amount of element change. For example, 18K color gold, the mother body is 75% Au, the alloy material of each ribbon is also 75% Au, and the remaining 25%, in addition to Ag, Cu, also added a small amount of Zn, Ni, Pb, Cd and other elements to produce different The color. After careful processing, you can make a colorful gold jewelry.

It is important to note the color of the colored gold. Although the color of each part of the gold is the same, the alloy materials and impurity elements are different for each ribbon. In the fluorescence spectrum analysis, attention should be paid to the complex matrix effect. The specific gravity change of the color gold caused by the different specific gravity of each element must be considered in the determination of the specific gravity method, and the measurement result must be corrected.

6, hollow gold, wrap gold: Anonymous thinking, hollow gold is the external closed, internal empty door gold jewelry, such as hollow heart pendant. That is a gold-passing wrapped in a layer on the copper wire K gold, copper, or an alloy material or a fake gold jewelry, pay special attention to identification.

The two main factors affecting the color of gold, namely the composition and structural characteristics of gold jewelry, are also analyzed. They are also the main basis for selecting the measurement method and correcting the results.