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The history and manufacturing technology of bone china mugs |
| Ceramic Mug From:Xinxiang Ceramic Mug Manufacturers 2023-4-18 |
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1.Introduction to China Bone Ceramic mugs
Bone porcelain, formerly known as bone powder porcelain, is also known as bone porcelain. Bone porcelain refers to the porcelain clay made by mixing bone powder with quartz, which is lightweight and milky white. When placed under light, the porcelain can be faintly transparent. During the production process, animal bone powder is added to the bone porcelain mugs, and it is internationally recognized that the bone powder content is between 43% - 45%, which is called high-quality bone porcelain mugs (FINE BONE CHINA)
Bone meal is made from beef, sheep, pig bones, etc Beef bone is preferred. This component can increase the hardness and transparency of porcelain, and its strength is higher than that of ordinary porcelain, so it can be thinner than ordinary porcelain. The higher the bone content, the easier it is to burn and crack during the production process, so the finished product is more expensive. The bone ceramic cup has a lightweight, dense and hard texture (twice that of daily porcelain), is not easy to wear and tear, has moderate transparency and insulation, and has a natural milky white color unique to natural bone powder.
The materials used for bone ceramic mugs are exquisite, with precise production and strict standards. Its regularity, whiteness, transparency, thermal stability, and other physical and chemical indicators require extremely high requirements. In the late 17th and early 18th centuries, porcelain has always been a patent in China. After the Industrial Revolution, modern Europe gradually developed its own porcelain making technology in the development of Venetian glass craftsmanship. They not only copied Chinese Blue and white porcelain and colored porcelain, but also developed many high-quality porcelain varieties.
In the 1980s, China successfully fired the first internationally recognized bone china mugs and exported it in large quantities. Bone china Chinese and Western tableware, with its high quality, style, and taste, has become a must choose porcelain for upgrading major star hotels. Famous catering units such as Beijing Shangri La Hotel, Beijing Hilton Hotel, Beijing Quanjude Hotel, Suzhou Sheraton Hotel, Qingdao Hardman Hotel, Zhongnanhai State Guesthouse, etc. have all adopted bone china products and won the love of consumers. Bone porcelain tea mugs, coffee mugs, family set tableware, and bone porcelain handicrafts have become ideal utensils for various companies and middle-class families, and are also the best gifts for relatives and friends. Bone china cups have gradually become the main consumer of high-end porcelain in China.
2.The Manufacturing Process of Bone China Mugs
The production of bone ceramic mugs mainly relies on silicon oxide, alumina, and calcium oxide. The higher the content of calcium oxide, the better the color. In nature, there are not many sources of calcium oxide, so animal bone meal is chosen as the source of calcium oxide. This is also the origin of the name of the bone china mug.
In fact, the so-called bone ceramic is a bone ceramic mug made from the ashes of herbivorous animals (mainly Ca3 (PO4) 2), mixed with high-quality kaolin, quartz and other auxiliary materials, and glazed at 1280 ℃. Generally speaking, adding 25% bone powder to the raw material can be called bone porcelain, but the best quality bone porcelain recognized in the world today is 45% -51% bone powder content, with cow bone being the best.
The production process of bone porcelain mugs includes grouting, molding, dehydration of gypsum molds, initial firing, glaze firing, and sticker baking processes. The bone porcelain cup is fired at high temperature to become a porcelain with high whiteness, high transparency, and delicate porcelain quality. During the firing process of bone porcelain mugs, high requirements are placed on their physical and chemical indicators such as regularity, whiteness, transparency, and thermal stability, resulting in a high scrap rate. Due to the exquisite materials used, precise production, and strict standards, the price of bone porcelain cups is higher than that of other porcelain varieties.
The unique firing process and the addition of bone carbon eliminate impurities in the porcelain clay, making bone porcelain appear cleaner, more delicate, transparent, lightweight, with few defects, and thinner than ordinary porcelain. It has a special sense of cleanliness visually, and its strength is twice that of ordinary porcelain, which is twice that of daily porcelain. The higher the content of bone powder, the relatively lower the composition of clay, which is more prone to cracking during the production process. This requires higher technology in forming, increasing the difficulty of firing, making bone porcelain cups more precious.
There are also high-end porcelain such as shell porcelain and pearl porcelain, which are similar to bone porcelain. Due to their high cost and almost no industrial production, bone porcelain mugs are recognized as the most high-end ceramic cups in the world.
3.Black spots in the production process of bone porcelain cups
The partial or complete appearance of black spots on the bone porcelain mug is called "smoking". This defect is due to incomplete oxidation or premature reduction of the body, which causes the carbon organic matter and low-temperature carbon deposits in the body of the bone ceramic mug to not be completely burned, and is sealed by the glaze layer. The surface of the bone ceramic cup is gray.
The factors affecting smoking analyzed by Xinxiang Ceramic Mug Manufacturer include:
1).During the oxidation stage of low and medium heat insulation, the oxidation is incomplete and some carbon remains in the body, resulting in a grayish black cross-section of the body. Especially when clay containing a large amount of carbon, such as coal gangue, is used in the body, the carbon in the body should be fully oxidized before the glaze layer melts. For products without carbon in the billet, oxidation should also be strengthened during the medium heat insulation stage, and special attention should be paid to coal fired intermittent kilns and thick tire products. This is because in intermittent kilns, the temperature inside the kiln is low and there is a lot of water vapor during ignition. In addition, the flue gas temperature is low at this time and the chimney suction force is weak. During the short period of time when adding coal and prying the furnace, the flame nature inside the kiln is a reducing atmosphere. At this time, not only can the carbon inside the billet cannot be eliminated, but it also causes carbon deposition on the billet. Especially when the moisture content of the billet entering the kiln is high, it is more likely to cause black spots on the bone porcelain mug. So, during the medium heat insulation stage (usually between 1000~1100 ℃), it is necessary to maintain a strong oxidizing atmosphere and have sufficient insulation time. That is to say, in the kiln operation, the thickness of the ash layer, fire layer, and coal seam on the furnace grate should be controlled to ensure good ventilation, a large excess air coefficient, a clear fire layer in the combustion chamber, and every time the coal is added, it must be burned thoroughly to fully oxidize the billet. Otherwise, if the amount of coal added is too high, the ash layer is too thick, the ventilation under the furnace is poor, and the combustion is not thorough, the flue gas containing free carbon generated in the combustion chamber will be stored in the kiln for a long time. At this stage, the porosity of the green body is the highest, and the adsorption is strong, making it easy to adsorb the flue gas, resulting in carbon deposition.
2). In the later stage of the reduction stage, the reduction atmosphere is too thick, that is, when the glaze has melted, the kiln still maintains a strong reduction atmosphere without timely turning into a weak reduction or neutral atmosphere, and the product is still in the reduction atmosphere. Therefore, CO in the flue gas decomposes at high temperatures, causing surface carbon, especially when using calcium glaze. Due to the severe carbon absorption phenomenon of CaO, the glaze smoke is most likely to form.
3). Analysis of Blackening of Bone Porcelain mug: The glaze formula is unreasonable. If excessive CaO or other fluxes are used, the glaze will prematurely produce liquid phase and melt, the vitrification range is too narrow, making it difficult to burn out the deposited carbon in a timely manner, or the temperature difference in the kiln is too large to ensure the atmosphere change of the bone porcelain mug, causing some products to be in a chaotic atmosphere or excessive sulfur in the fuel. If the sulfur containing gas stays in the kiln for too long, the sulfur will strongly seize the oxygen in the flue gas, making the reducing atmosphere thicker, Easy to produce smoke defects.
4.Daily maintenance methods for bone porcelain mugs
After drinking coffee or tea using bone china cups, we need to clean them. Because bone china mugs are thin and have a high whiteness, they are harder to clean than ceramic coffee mugs.
When the surface of the bone porcelain cup is stained with oil, clean it with warm water, and the water temperature should not exceed 80 ℃; If it is difficult to clean, add a small amount of edible vinegar to water and then clean.
If the outer wall of the bone porcelain cup is scratched, it can be gently polished with toothpaste; When using a damp cloth or hand to clean, attention should be paid to the force, not too much, to avoid scratching the porcelain.
After use, bone china mugs often leave coffee or tea stains. To clean them, add vinegar or lemon juice to warm water and slowly clean them manually.
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