Traditional ceramics and glass are neither metals, nor plastics, nor wood. Compared with metals, traditional ceramics and glass are non-conductive and have poor ductility; compared with materials such as plastics and wood, traditional ceramics and glass are not organic and have poor elasticity and cannot be burned. The main chemical elements contained in traditional ceramics and glass are all silicon and oxygen, and they belong to silicate products. They not only have similar chemical compositions, but also share many similarities in performance and characteristics. In addition to the above characteristics, they are all insoluble in water, highly heat-resistant, have a hard texture, and are prone to breakage. So ceramics and glass really belong to the same "family"!
Although they share many similarities, ceramics and glass also have many differences. Their appearance is obviously different. Ceramics are opaque, while glass is transparent and shiny. Even when talking about ceramics, it is a general term for a variety of pottery and porcelain, which have different origins, appearances, and characteristics.
Among many silicate products, pottery was the earliest to be invented. As early as 8000-2000 BC (the Neolithic period), the Chinese invented and produced a variety of pottery, using the most common clay as the raw material. Wet clay is flexible and plastic, and can be kneaded into certain shapes (such as clay blanks). After it is slightly dried, it can be carved, and after it is completely dried, it can be polished. If the formed clay blanks are burned at 800°C in the fire, they will become pottery. This kind of material, which is prepared, formed, sintered, and refined, is scientifically called traditional ceramics.
The difference between porcelain and ceramics lies in the difference in raw clay and firing temperature. To make white porcelain, high-quality raw clay, such as kaolin, is selected, and the firing temperature is increased on the basis of ceramic firing. The clay then becomes porcelain. The firing temperature of pottery is 800-1000°C, while that of porcelain is usually 1200-1400°C.
Due to the difference in raw materials and firing temperature, the structure of pottery is relatively loose, with certain air permeability and water absorption; while the structure of porcelain is denser, with a smoother surface and greater hardness. It is impermeable to water and gas, and is more resistant to high temperatures and corrosion. Of course, today, there are many varieties of ceramic and glass products, and their chemical compositions, production methods, firing temperatures, and quality performances often overlap and intertwine, with no clear boundaries. Some new products are like both ceramics and porcelain, so they are often referred to as a single category, called ceramics.
Compared with ceramics, the birth and production of glass is much later, and the large-scale production of glass products is even later. The raw materials for the production of ordinary glass today are mainly a mixture of relatively pure quartz sand, soda ash, feldspar, and limestone. When making glass, there is no need to use clay blanks like ceramics. Instead, the raw materials are simply heated to 1300-1600°C, and the quartz sand and other raw materials will become a molten viscous liquid glass. Then, through mechanical processing, flat glass or glass tubes can be obtained, and glass bottles, glass crafts, etc. can also be made through processes such as blowing, pulling, bending, and pressing. After the formation of glass products, they can also be further processed. For example, in middle school chemistry classes, with the help of gas lamps and tweezers, a glass tube can be heated and softened, then processed into a test tube, blown into an ampoule, or bent into a right-angle conduit.
In summary, the main differences between glass and ceramics are: the choice of raw materials is different; the chemical composition is different; glass melts when heated and is an amorphous substance, while ceramics has crystallinity; and the production processes are different.