In China ancient porcelain, especially the exposed part of kiln-changed porcelain, there are often red burnt products with different shades, ranging from dark brown to light red. Because it resembles the red color in volcanic rocks, people in the industry call it "flint red". With regard to the reasons and physical and chemical mechanism of the appearance of "flint red" on porcelain, the author and Ma Ping, the curator of the Ancient Porcelain Museum in Anwuzhai, co-authored two monographs, Discrimination of "flint red" on ancient porcelain and Re-discussion of "flint red" on ancient porcelain, which were published in the No.1 12 issue of Collection magazine respectively, and included in my book On Porcelain Collection. This paper only briefly introduces the identification of flint red from the perspective of ancient porcelain identification methods. "Flint red", which some people call "kiln red", "yellow overflow", "yellow coat" or "flint glaze", refers to the orange-red or orange-yellow phenomenon in the exposed parts of ancient porcelain, especially Jingdezhen porcelain and Longquan kiln porcelain since the Yuan and Ming Dynasties (it has also been found in other ancient porcelain kiln products, so I won't go into details). Although it is generally called "flint red", its manifestations and causes are varied. The author divides it into four different forms: fetal red, kiln red, brush red and false red. "Fetal red" means that the iron element contained in the fetal body of the utensil is enriched to the exposed part of the utensil in the form of iron ions during the firing process, but it is secondarily oxidized and attached to the exposed surface during the cooling process of the utensil. Therefore, the general "fetal red" usually shows the "field effect", that is, the closer it is to the dividing line of fetal glaze, the lighter it is. The bottom of a blue-and-white three-legged drum furnace in Hongzhi Folk Kiln in Ming Dynasty has the phenomenon of "fetal red", and its "scattered effect" is very typical (Figure 1). "Fetal red" can be divided into two phenomena, one is the fetal red existing in the unglazed tread as shown in Figure 1, and the other is the phenomenon that iron ions not escaped by air are oxidized twice through brown eyes on the glazed surface and loose gaps in the tire, thus flint red appears under the glaze (Figure 2). In the past, ancient porcelain researchers may not pay much attention to this phenomenon, so they have never mentioned it. However, objectivity is of paramount importance. Whether people notice it or not, it exists in ancient porcelain. Probabilistically speaking, it often appears in places where the glaze of kiln furniture with high iron content in tire mud is thin and there are brown eyes communicating with the outside world, or near the seam of tire glaze, or where the glaze is extremely thin. These places are the most convenient channels for iron ions to escape from the inside of the tire to the outside, so they are also the places where iron ions are most easily oxidized and attached to the tread. "underglaze tire red" exists not only in Jingdezhen porcelain in Yuan, Ming and Qing Dynasties, but also in Yaozhou kiln porcelain in Song and Yuan Dynasties, Longquan kiln in Song and Yuan Dynasties and other porcelain kiln products. "Kiln red" is the result of external factors during the firing of porcelain in the kiln. The performance characteristics of kiln red are as follows: 1. The color distribution does not appear around the glaze combination circle like tire red, but can appear in all exposed tires and even large and small glaze areas inside and outside utensils. Secondly, the crystal of Kiln Red does not show the "scattering effect", but presents an irregular flaky distribution. Thirdly, kiln red and fetal red sometimes appear on ancient porcelain at the same time. This phenomenon is common on blue-and-white and glazed red porcelain in the Yuan Dynasty (Figure 3), and the bottom of the porcelain is covered with exposed tread patterns. It may be related to the use of river sand to pad porcelain during firing. Kiln red sometimes appears alone, of course, there are only tire red without kiln red. The difference in the appearance of flint red proves that the formation reasons of fetal red and kiln red are different, that is, fetal red is produced from the internal cause of porcelain tires and kiln red is produced from the external cause of porcelain, and there is no necessary connection between the appearance of the two on ancient porcelain objects (Figures 4 and 5). "Brush red" is a phenomenon of artificial flint red. This kind of artificial flint red can be divided into two situations: one is a technological means in the production of ancient porcelain, which was often used at the bottom of bare-tire porcelain in Yuan Dynasty and early Ming Dynasty (Figure 6). Another kind of red painting is the method of making fake flint red with modern antique porcelain. False red is artificial false flint red, which is not produced by secondary oxidation after iron precipitation in the porcelain tire at high temperature, nor by iron precipitation in the kiln wall, kiln bed and sagger at high temperature and adhesion to the exposed part of the porcelain tire, but by people consciously. So, how to dialectically recognize and identify the phenomenon of flint red on porcelain? First of all, the appearance of flint red on porcelain is not divided by historical dynasties. Some people say that there is flint red on porcelain in Yuan and Ming Dynasties, but there is no flint red on porcelain in Qing Dynasty. This view is wrong and divorced from reality. The appearance of flint red on porcelain is not divided into official kilns and private kilns. The fact is that there are many flint red phenomena in folk kilns, but few in official kilns. Whether and how much flint red appears depends entirely on the iron content in the porcelain tire and the iron ion content in the atmosphere in the kiln. Secondly, dialectically understand the role of flint red in the identification of ancient porcelain. Before the end of the last century, the makers of antique porcelain had not developed a method to make antique porcelain show real tire red and kiln red. The "scattering effect" of fetal red is to drag the vessel out with a brush dipped in water with high iron content before entering the kiln. Kiln red is burned by putting bran ash at the bottom of the vessel when the kiln is "full". These fake flint reds can fool amateurs, but not experts. However, since the beginning of this century, some antique porcelain workshops have developed new doorways in mud and firing atmosphere, and flint red on fired antique porcelain can be confused. Only through flint red can we identify whether ancient porcelain has lost its accuracy in some specific objects. Therefore, flint red can only be one of many factors in the comprehensive identification of porcelain, not the only criterion to distinguish between true and false ancient porcelain. Of course, if it is accurately judged that the flint red of a piece of porcelain is false in the identification, then this discovery will help us to be vigilant and reveal the pseudo-fake nature of the ware from other elements. And if there is no doubt about the flint red on an object to be identified, then we must also be vigilant and strictly check all the elements before we can make a decision without doubt. Third, the inspection of flint red should be cautious. If the tire red and kiln red on an antique porcelain are fired by modern antique technology, we must find another way to identify them; If its tire red and kiln red are painted artificially before and after firing, there must be something that violates the law of natural formation and reveals the defects of artificial traces. For example, the tire red on some antique porcelain also presents a "scattered effect", but if you look closely at the seam line of the tire glaze, some exposed tires have no flint red, indicating that there is a pen leakage phenomenon when painting by hand; Some kiln reds are also distributed in sheets, but if you look closely, there are brush marks. As for the "painting red" on the bottom of ancient porcelain, we should not only find out the dynasties that used this technique in history, but also adhere to the principle of comprehensive appraisal and analysis, so as to avoid the one-sided thinking mode of turning a blind eye and getting a glimpse of the leopard. Fourth, adhere to the line of understanding from practice and master the characteristics and differences between true and false flint red from both positive and negative aspects. First of all, we often observe various characteristics of flint red on some ancient porcelain specimens. Now some people mix pieces of antique porcelain with pieces of real antique porcelain and sell them. Be especially careful. The second is to observe and analyze the phenomenon of flint red on antique utensils, ask experts for knowledge and solve its formation method. 5. "Paste the rice bottom" is a unique expression of flint red on the exposed tire bottom objects of Ming Chenghua. During the molding period, river sand with high iron content is used to lay the sagger bottom, and the exposed green body is directly placed on the sand mat to burn the kiln. After the device is completed, the bottom is easily stained with sand and covered with kiln red (Figure 7). This phenomenon not only exists in folk kilns, but also appears in some official kilns, which has become a unique phenomenon in Chenghua. Sixth, don't treat "sauce mouth" as flint red. In the early Ming, late Ming and early Qing dynasties, the mouth edge of folk kiln utensils often showed a circle of different shades of sauce red, ranging from iron brown to orange red. This is a unique feature of the times, and it is about the legacy of the "purple mouth and iron feet" of Ge Kiln in Song Dynasty. In the Ming dynasty, the mouth of the sauce on Yong musical instruments was bright and orange-red, and it was called the mouth of sandalwood (Figure 8). But this kind of "sauce mouth" is made by coating sauce glaze on the mouth of the vessel, not flint red. Expert ma's analysis and comment on flint red,