Introduction to the first author: Yin Baozhong, senior consultant of the Third Professional Committee of Artifacts of China Insurance Association, former researcher of Shanghai Institute of Silicate, China Academy of Sciences.
I. Introduction
With the improvement of people's material civilization and spiritual civilization, people's requirements for their own image are correspondingly higher and higher. Accessories are no longer simply considered from the perspective of maintaining or increasing value, but gradually match with factors such as clothing, hobbies and occasions. Therefore, it is hoped that the accessories and spare parts will be diversified. At the same time, natural mineral resources such as diamonds, precious stones and jade are increasingly scarce, so the price is more expensive, and the color, shape and uniformity are greatly limited. Therefore, people's demand for artificial products is more urgent, and they also hope that it is rich in variety, bright in color, vivid in image and low in price. At present, using inorganic amorphous materials or glass to imitate a large number of colorless or colored natural gems and jade has reached the level of confusing the real with the fake. From the perspective of appearance and physical and chemical properties, the product can be no different from the natural ore processed product by adjusting the composition, because glass can be made into homogeneous amorphous or multiphase materials containing droplets and trace metal particles. In this way, fashionistas wearing ornaments can be gentle, more elegant, physically and mentally happy, meet the growing psychological demand for beauty, choose a wide range of categories, spend less economically, and make people's quality of life more perfect.
This paper briefly introduces the technological principle of glass imitation diamond (commonly known as diamond in folk), various imitations of colored gems, jade and colored glass, and the application of corresponding products in the market.
Second, the process principle
Glass is not as strict as synthetic gems. As we all know, synthetic rubies, synthetic sapphires or synthetic crystals require the chemical composition and physical and chemical properties to be consistent with nature. Under artificial control, these products can reduce the impurity content to a very low level. Therefore, some synthetic products have better physical and chemical properties than natural products, and are used in cutting-edge technology and national defense industry, such as synthetic crystals as basic materials for manufacturing semiconductor chips. If glass is used to imitate all kinds of natural gems, the appearance will be more similar, and the chemical composition is not required to be the same, only the physical and chemical properties such as density and hardness are required to feel similar. After the glass block with similar appearance to the imitation object is made, it needs to be ground into a polyhedron like a natural gem, observed and compared from all angles under natural light, and then fine-tuned in chemical composition, so as to make the imitation gem product very similar to the natural gem.
Melting the glass substrate of imitation gem products can be operated by electric furnace and platinum or corundum crucible in the laboratory. The quality is easy to control, the performance is excellent and the repeatability is good, but the output is low and the cost is high. It is usually produced in a factory with a large-capacity oven or a small pool furnace. As long as the process requirements are strictly followed in the operation process, qualified substrates can be obtained.
For the selection of raw materials, the general requirement is that the content of impurities such as iron should be as low as possible, so as to make the products bright and crystal clear.
For the introduction of oxide components in materials, it is necessary to change the selected mineral raw materials and chemical raw materials according to the requirements of imitation objects and melting atmosphere. For example, alumina can be introduced from alumina, aluminum hydroxide and feldspar respectively, but only one of them can be used under certain conditions; Selenium and cadmium sulfide can generally be used as red or golden raw materials, but they are not suitable for systems with high lead oxide content; Similarly, some green products can only choose one or more combinations of copper oxide, copper sulfate and cuprous oxide as raw materials for introducing colorants.
The temperature of molten glass is about 1400℃. Due to the change of chemical composition of the material, it needs to be adjusted accordingly, and the length of melting time will be selected in a wider range.
Three. Results and discussion
1. Glass imitation diamond
The common glass imitation diamond is colorless and transparent, commonly known as "diamond" in folk, and can also be colored. These glass imitation diamonds are mainly used as decorations, and their prices are low. At present, the physical and chemical properties of materials are only the comprehensive data of coated products and metal substrates, and the exact value of glass substrates has not been reported. Last year, researchers from Shanghai Institute of Silicate, China Academy of Sciences helped Zhejiang enterprises digest, absorb and localize (innovate) semi-mechanized glass diamond-like grinding equipment and technology and glass materials imported from Czech Republic. In the discussion, the Czech expert group did not explicitly put forward higher requirements for the performance of glass substrates. We think that the content of iron impurities in the raw materials for melting the glass substrate should be low, so that the glass made is highly transparent and colorless, without stripes and small bubbles, and can reach the optical glass fully and uniformly, but the chemical stability needs to be good, because the glass particles need to be polished into semi-finished products with 17 surface or other shapes after being treated with acid and alkali solutions, and then subjected to silver plating and other technological processes. Its handicrafts are shown in figure 1.
Figure 1 glass imitation diamond (commonly known as rhinestone) handicrafts
If the variety is single, colorless and transparent glass, diamond-like carbon substrate glass can be produced in factory kiln or even small pool kiln because of its large dosage. The glass substrate for producing various colored glass imitation diamonds can be melted in a kiln or a slightly larger electric furnace in the laboratory according to the quantity and color, and it is not suitable for production in a small pool furnace with a small number or many colors, because it is difficult to completely clean the remaining colored glass in the furnace, because some inorganic colorants (Yin Baozhong et al.,1982; Package, etc., 1982, 1983) has very strong coloring ability.
According to the requirements of diamond-like crystal decoration of glass, the refractive index of glass substrate should be as high as possible, but a certain viscosity should be maintained to make it easy to form, and the material should be long, and there should be no tendency to crystallize. In addition, the cost should also be considered. After all, the price of glass imitation diamond is not high, but it is profitable.
2. Glass imitates colored gems.
It takes a long time and a long span to imitate all kinds of colored gems with glass. Because of the rich color systems involved, each color system should be subdivided according to the requirements of color depth and light and shade. Some color series products are very sensitive to the melting atmosphere in the process, and the slightly oxidized atmosphere will make the colorant fade or even colorless; On the contrary, some components do not develop color in a slightly reducing atmosphere. If the color of the product has good repeatability, the rules must be strictly followed in the process operation. Some factories find some bills of materials and copy them for no reason, so that the products are sold in the form of "supermarket" because the color system is different every time and cannot be repeated, and the finished products are supplied at one time.
After melting in the laboratory or factory into a suitable glass block with uniform stripes and bubbles, please cut and grind it into imitation gems with the same specifications and sizes as those provided by the seller, observe the subtle differences between them from all angles under natural light, and then make adjustments to keep them as consistent as possible. Therefore, in addition to the glass materials with similar density and hardness as close as possible to the imitation object, it is also necessary to accurately modulate the variety and quantity of colorants. Sometimes, the amount of colorant in a colored glass is very small, but more than three combinations are needed to achieve a realistic imitation effect. Fig. 2 is a sample of a part of glass imitating colored gems.
Fig. 2 gem ring-like surface of colored glass.
After years of efforts, many glass varieties imitating colored gems have appeared in the jewelry market, which are dazzling and beautiful, forming a certain commercial scale.
The requirements of a famous American artist for his team to produce large-scale glass artworks are as follows: porcelain glass is uniform, bubble-free and stripe-free; Bright colors and many varieties; The thermal expansion difference of various colored porcelain glasses is less than 1, and the actual requirements are almost zero. Each jar of glass needs to be attached with the measurement data of stress difference polarizer with expansion coefficient; The surface tension of glass materials should not be too small, so that the boundaries of welding surfaces between glasses are clear and tidy, and there are other strict technical requirements for size specifications. These are also the requirements for our production of colored glass imitation gem matrix.
On the basis of the above-mentioned gem imitation work of colored glass, we added porcelain-producing ingredients to the raw materials of colored glass production to make products that customers need. Foreign businessmen have set up distribution companies in the United States and Australia to provide goods made in China to the European and American markets.
3. Glass imitates jade
To imitate jade with glass, we must first emulsify the glass. In order to emulsify glass, it is necessary to introduce a certain amount of emulsifier components into raw materials for glass production, or use chemical components that are immiscible with each other (Yin Baozhong et al., 1984). With the decrease of melt temperature, phase separation will occur, and opaque or translucent opaque glass can be made due to the different refractive indexes between the matrix and the micro-dispersed phase distributed in it. If you want to imitate jade, you should control the quantity and size of particle emulsifier in the material, not too much and not grow up.
In order to facilitate the process operation and simplify the process, a small amount of emulsifier and components to prevent the growth of microcrystals or microbubbles are generally used. In the melting process, the temperature should not be too high and the time should not be too long, so as to avoid the disappearance of emulsifier in the melting process.
Figure 3 Jade Crafts
The materials made by this method can be imitated into jade-like varieties (Figure 3). If it is colored (Yin Baozhong et al., 1992), it is necessary to add a small amount of colorant to the composition of the material in advance. We copied light gray green Xinjiang Hetian jade beads and exported them to neighboring countries. In the post-treatment operation of the above process, it is necessary to avoid pulling the emulsifier microcrystals or microbubbles in the material together with the glass material to grow fibers, because the refractive index difference between them is obvious, and even if they are irregularly arranged, the final goods will have a cat's eye effect at a certain angle under the irradiation of natural light.
4. Coloured glaze
China has colored glass since ancient times, which is actually modern colored leaded glass. Ancient Chinese artists have superb skills in making glazed works of art, which makes glazed works of art very beautiful. But for a long time, we didn't see these glazed artworks circulating in the market. With the advocacy of several artists from Taiwan Province Province, we have successfully developed the ancient glazed works of art in China, with new development and new creativity. In recent years, many glazed artworks have been sold in the market, some of which have become collectibles and some are precious gifts for distinguished guests. Among them, the glazed artworks produced by Wang Xiajun Group and Yang Huishan Zhangyi Group are particularly creative.
Figure 4 Coloured glaze
The process of producing colored glass is very demanding, because this kind of "crystal" glass with high lead oxide content can't use ordinary colorants with lower requirements for atmosphere, which will make the color of colored glass dark or even gray, and the color will be worse after dewaxing and casting. At present, the content of lead oxide is still developing in a high direction, and the mature one in China is the one with a slightly lower lead content. Because of the change of composition, the corresponding process parameters will also change, such as the concentration and time of acid polishing treatment, sintering temperature and so on.
The requirements for glass materials are that the linear expansion coefficient is consistent and the density is similar, and the glass powder will not be uneven during sintering and will not expose the welding surface.
Coloured glaze is mainly used as handicrafts, but it can also be used as raw materials for processing into jewelry such as gems. Because of its high refractive index, the polished product can be crystal clear and bright, and the corner glaze can also be fully used for other purposes. See Figure 4 for raw materials of coloured glaze.
Four. conclusion
1) glass can be made into high-quality imitation diamonds (commonly known as diamonds) and glass substrates, and can also be imitated into lifelike natural colored gems and jade. There are already corresponding commodities and derivative commodities in the market, forming a considerable category. There is still great potential for quality improvement.
2) We should increase investment and innovative development in the technical research and equipment improvement of glass melting molding equipment, glass imitation diamond (commonly known as diamond) and gem grinding, so as to stabilize the quality and finished product at a very high level, greatly reduce the cost and make a higher profit.
refer to
Yin Baozhong, Guo Changlin, Lu Changwei. 1986. Study on the color development process of golden red glass. Journal of Silicate, 14( 1):88.
Yin Baozhong, Huang Xihuai. 1984. X-ray study of carburized glass. Journal of Silicate, 12(3):3 13.
Yin Baozhong, Zhao Xiaowei, Maryton. 1992. EX-AFS study on the structure of selenium arsenic glass. Journal of Inorganic Materials, 7(3):28 1.
Bao Zhongyin. 1982. Size of precipitated silver halide microcrystals in photochromic glass. J. Not crysta. Solid, 52:567.
Yin Baozhong, Shen Juyun. 1983. SAXS study on photochromic glass. Gladstick, 56:986.