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The similarity between the microscopic characteristics of the Song Dynasty official kiln and the Ming and Qing dynasty imitation official porcelain is that Cao Zhao said in the "Treatise on the Ancient Essentials": "The official kiln ware, the Song Xiu Neisi burner, the soil vein is fine, the color is green and pink, the thickness is different, there are crab claw patterns, purple mouth iron feet, and the good color is similar to the Ru kiln." These descriptions provide a high degree of generalization of the outward characteristics of Song Dynasty official kiln porcelain. Song Dynasty official kilns and Ming and Qing imitation official celadon glazes are mainly presented as cyan, with different shades. Glaze is generally textured, with varying texture sizes and densities. The glaze texture is like jade, and most of the utensils are thin along the glaze, revealing a certain tire color, showing the phenomenon of "purple mouth". The part of the glazed exposed tire is circled, and due to the high content of iron oxide in the carcass, it shows an iron brown color after firing, that is, the phenomenon of "iron foot". Through the observation of the microstructure of these 45 pieces of celadon porcelain, this paper summarizes the commonalities in the microstructure from the aspects of glaze characteristics, glaze characteristics and tire glaze intermediate layer characteristics. 3.1.1 Glaze characteristicsa, glaze spots: Song Dynasty official kiln celadon glazes often see spots with a diameter of several hundred microns to two thousand microns in size, these spots have black, yellow and other different colors, some of which have bright metallic luster. There are also various spots on the glaze of Ming and Qing imitation official porcelain, but it is less than that of the Song Dynasty official kiln. Spots may be formed by the unevenness of the glaze, the lack of fine grinding, the enrichment of the iron in the glaze on the glaze, or the fact that certain substances fall on the glaze surface during firing. (Figures 1 to 4) shows microscopic pictures of glaze spots of different samples of celadon in the Song Dynasty official kiln. b. Bubbles and brown eyes with glazed discoloration: In most Song Dynasty official kilns and Ming and Qing dynasty imitation official porcelain glazes, discolored bubbles and brown eyes of different sizes and shades can be observed. The black bubbles in (Fig. 5) are caused by bubble holes and later pollution, (Fig. 6 to 8) are microstructure diagrams of brown eyes on the glaze of different samples.
c. Glaze reduction: Most song dynasty official kilns and Ming and Qing imitation official porcelain glazes have a local unglazed phenomenon, that is, the phenomenon of shrinking glaze. The shape of the glaze is generally round or oval, the area is large or small, and there are also long strips, which generally appear at the junction of the bottom and wall of the utensil. (Figures 9 to 12) are microscopic pictures of the glazing shrinkage phenomenon of Song Dynasty official kilns and Ming and Qing imitation official porcelain.
3.1.2 Microscopic characteristics of glazea a, glaze opacity: Under the microscope, the glaze of song dynasty official kilns and Ming and Qing imitation official porcelain was observed, and it was found that in addition to bubbles, there were some white substances similar to flocculents in the glaze, and the glaze was not transparent. (Fig. 13 to 16) is a microstructure diagram of the glaze. b. Bubbles: There are rich bubbles in the glaze of Song Dynasty official kilns and Ming and Qing imitation official porcelain, with different sizes and staggered, some sample bubbles are sparse, and some samples are densely packed. (Fig. 17 to 20) is a microscopic picture of bubbles in the glaze of different samples.
In addition, there are often small dots of different colors under the glaze, and when they are enlarged, a cavity-like structure is observed in the glaze, which may be formed by many micro-bubbles coming together. (Fig. 21 to Fig. 24) is a microscopic picture of large bubbles in the glaze.
C. Grain pieces: Southern Song Dynasty official kilns and Ming and Qing imitation official porcelain glazes generally have grained pieces, and the size and density of the texture are different. Some samples have a uniform thickness and yellow color; some samples have "golden wire" stripes, that is, thick black stripes and fine yellow stripes. Most samples have lighter, or even colorless, finer-grained patches that appear extremely light yellow or colorless under the microscope. (Fig. 25 to Fig. 28) is a microscopic picture of the glaze grain sheet.
There is also a kind of grain that is invisible to the naked eye, only seen under the microscope, this kind of grain is very thin and not long, does not crack in the direction of vertical glaze, does not run through the glaze layer, which is the oblique opening sheet formed after the porcelain comes out of the kiln (Figure 29) and (Figure 30) is the microstructure picture of the oblique opening piece.
3.1.3 Tire glaze middle layer features In the nondestructive testing of song dynasty official kilns, the white and yellow tire glaze intermediate layers were found at the fractures of two samples. (Fig. 31) and (Fig. 32) are pictures of the microstructure of the intermediate layer of the tire glaze.
3.1.4 Other features In the microscopic observation of some samples, it is found that there is fracture under the glaze, such as (Figure 33) and (Figure 34) of the "Ya" type fracture, as well as simple cracking, such as (Figure 35) and (Figure 36).
3.2 Differences in the microscopic characteristics of Song Dynasty official kilns and Ming and Qing imitation official porcelain3.2.1 The microscopic characteristics of glaze and the ring-like pattern in carcass Among the 45 pieces of Song Dynasty official kilns and Ming and Qing imitation official porcelain, the microstructure of the glaze of Song Dynasty official kiln utensils was significantly different from other samples. These 7 utensils are all hexagonal diamond fancy plates with three spikes at the bottom, and the dimensions are also very similar. There are macula on the glaze, the number of macula and the shade of color have a certain difference, the bubbles in the glaze at the macula are blurred, the glaze seems to be bleached, and only the bubbles in the glaze can be seen clearly without the macula. (Fig. 37 to Fig. 40) is a picture of the microstructure of the glaze.
The seven hexagonal diamond fancy plates have more glazed exposed tires, and the glaze grain is denser, and according to incomplete statistics, the glaze thickness is about 1.6MM. Near the bottom of the disc, the carcass of the three hexagonal diamond fancy discs can be seen in a ring pattern. As shown in Figures 41 to 44, this indicates that the carcass may have used a wheeling tool when forming or repairing the blank.
3.2.2 Comparing the grain pieces of Song Dynasty official kiln porcelain with the ming and qing imitation official porcelain glaze, it is found that the grain pieces of the song dynasty official kiln porcelain glaze are generally short and dense, while the grain pieces of the ming and qing imitation official porcelain glaze are thin and long, see (Figure 45) and (Figure 46). In addition, Ming and Qing imitation official porcelain is straighter than the glaze of Song Dynasty official kiln porcelain, and the curvature is small. See (Figure 47) and (Figure 48).
3.2.3 The phenomenon of uneven color of the local area of the glaze appears in the two imitation official porcelains of the Ming and Qing dynasties with uneven glaze color, that is, the glaze color of some areas is white, which can be observed from (Figure 49) and (Figure 50), while the samples of the Official Kiln of the Song Dynasty basically do not have this phenomenon.
4. Results and analysis of the elements of 45 pieces of Song Dynasty official kiln porcelain and Ming and Qing imitation official porcelain show that there are 4 samples of Song Dynasty official kiln porcelain (GCQS-1584, GCQS-1586, GCQS-1602, GCQS-1612) glaze main and secondary elements and trace elements are different from other samples of Song Dynasty official kiln, but similar to the element composition of Ming and Qing imitation official porcelain glaze The analysis of the primary and secondary elements and trace elements of the glaze of 1 sample (GCQM-1631) in the Ming and Qing dynasties is similar to that of the Song Dynasty official kiln porcelain, and in the statistics, we assign these samples to the corresponding categories according to the elemental analysis results for data processing. The elemental analysis results of the seven hexagonal diamond fancy plates of the Song Dynasty were quite different from those of other Song Dynasty samples and were not included in the statistical analysis of the data. 4.1 The elemental analysis results of the glaze glaze glaze of the Song Dynasty official kiln and the Ming and Qing dynasty imitation official porcelain glaze show that the glaze contains 7.55% CaO and 4.33% K2O (the average of all samples), which belongs to the calcium glaze or calcium alkali glaze, and the firing temperature is about 1200 degrees (3) (4), at high temperature, physical and chemical reactions are easy to occur between the tire glaze, forming the middle layer of the tire glaze. According to incomplete statistics, the official kiln celadon glaze thickness of 1 ~ 1.8MM, the glaze has a certain viscosity at high temperature, the bubbles formed by various factors are not easy to escape in the glaze, and the micro bubbles are easy to gather together to form large bubbles during the firing process. During cooling, large bubbles may form vents (5) or brown eyes in the glaze. Affected by factors such as glaze thickness, firing temperature, viscosity and surface tension when glaze melts, and bonding force between blank glazes, the glaze surface will have a local unglaze or shrinkage phenomenon (6). During the cooling process, due to the mismatch of the coefficient of thermal expansion of the tire glaze, the glaze is subjected to tension stress, and the glaze appears grained. From the above analysis, it can be seen that the appearance and microscopic characteristics of the Song Dynasty official kiln porcelain are determined by its glaze raw materials and firing process. 4.2 Similarities between the microscopic characteristics of song dynasty official kilns and Ming and Qing imitation official porcelain Song Dynasty official kiln porcelain are simple in shape, with fine glaze like jade, and the style is natural and simple. The imitation official porcelain of the Ming and Qing dynasties paid attention to imitation of its glaze color, and did not pay attention to the imitation of its instrument shape, that is, the shape of the god was not similar; some imitations were not only realistic in the glaze color, but also paid attention to imitation in the shape, and the god-like shape was also similar. No matter what kind of imitation, the jade texture glaze of the Song Dynasty official kiln is the goal pursued by the imitators. Studies have shown that the artistic effect of the Song Dynasty official kiln glaze with a strong jade texture is because the glaze contains a large number of calcium feldspar crystals and bubbles, forming a sufficient scattering source, so that the glaze produces an emulsion effect (7) (8) (9). (Table 2) Is the statistical result of 38 pieces of bubbles in the glaze of Song Dynasty official kilns and Ming and Qing imitation official porcelain. It can be seen from (Table 2) that the diameter of the glaze bubbles of the Song Dynasty official kilns and ming and qing imitation official celadons is between more than ten microns and three hundred microns, mainly distributed between 30 and 180 microns, and there are more than 70 to 800 bubbles in the glaze per square centimeter area. It is these bubbles of different sizes and staggered patterns that play a part of the role in the jade texture of the Song Dynasty official kilns and the Ming and Qing Dynasty imitation official porcelain glazes.
Song Dynasty official kiln porcelain firing temperature is lower than that of Ming and Qing imitation official porcelain, there is unmelted glaze, a large number of bubbles and newly generated crystals in the glaze, these factors have a certain hindering effect on the direction of the grain piece, so the grain piece of the Song Dynasty official kiln porcelain is more curved, and the Ming and Qing imitation official porcelain, firing temperature is higher, the crystal phase in the glaze is relatively small, and the direction of the grain piece is less obstructive, so the grain piece of the Ming and Qing imitation official porcelain is straighter.
V. Conclusion (1) The microscopic characteristics of the Song Dynasty official kilns and Ming and Qing imitation official porcelain are generally similar, and the glaze surface has spots, brown eyes, holes, glaze shrinkage and other phenomena; there are a large number of bubbles in the glaze, and the glaze has grains of different shades and thicknesses; the tire glaze is easy to form an intermediate layer. These microscopic characteristics are determined by their glaze raw materials and firing process. (2) The jade texture of the official kiln glaze of the Song Dynasty was the goal pursued by the Ming and Qing imitators, and the bubbles in the glaze played a part of the role in the jade texture effect of the official kiln porcelain glaze. Although the element composition of the Ming and Qing imitation official porcelain glaze is different from that of the Song Dynasty official kiln porcelain, the firing temperature has also been improved to a certain extent, but the effect of the glaze jade texture and the size and density of the bubbles are not much different, which shows that the firing of ming and qing imitation official porcelain has fully mastered the role of bubbles on the glaze texture, and can achieve the same glaze texture by adjusting the firing process in the case of glaze change. (3) Affected by a variety of factors, the glaze pattern pieces of Song Dynasty official kiln porcelain are generally short and dense, while the glaze pattern pieces of Ming and Qing imitation official porcelain are generally rare and long. Due to the high firing temperature of Ming and Qing imitation official porcelain and the relatively small crystal phase in the glaze, the grain piece is straighter and less curved than the Song Dynasty official kiln porcelain piece. (4) In the collection of Song Dynasty official kiln porcelain, there are 7 pieces of hexagonal diamond fancy dish microstructure is different from other official kiln porcelain, the glaze looks like it is melted under the microscope, the bubble information in the glaze is not obvious, and the ring-like traces in the carcass can be observed, which may be caused by the use of wheeling tools when molding or repairing the blank. (The picture and text are from the Internet, and the copyright belongs to the original author)