They may be very similar in appearance, but in fact, there is a definite difference between them. Everyone is familiar with the phenomenon that many authors on websites use these terms interchangeably, claiming that they mean the same thing, sometimes calling all ceramics by one word – porcelain. This is wrong, because it misleads many readers.
Let’s look into what the errors are and correct them.
The most important thing I would like to bring to your attention, readers:
Porcelain is only a type of pottery, while not all pottery is porcelain.
Pottery, faience, majolica, terracotta, stoneware, chamotte, hard porcelain, soft porcelain, bone china, paper clay – these are different types of ceramic material and products made of them, depending on the use of different types of clay and additional ingredients. Each of these materials has its own unique characteristics and properties.
Ceramic is a general term that describes any product made from natural clay mixed in various formulas with water and in some cases with organic materials. Such a composition is shaped, decorated, usually covered with a glaze, and the material is hardened by heat by firing in a kiln.
The composition of the clays used, the type of additives, the temperature and the firing time determine the quality and hardness of the final product. Since these variables can be controlled by different parameters, there are many different types of ceramics.
Therefore, once again, ceramics is a broad category that includes as subcategories faience, earthenware, terracotta, stoneware, hard porcelain, soft porcelain, bone china, paper clay and more.
Faience is the earliest type of stoneware. Products are made from red or white clay, baked in a kiln at low temperature, usually 1000-1080 ° C. Since this type of clay does not reach a vitreous state during the firing process, earthenware is more porous and must be covered by an additional thick enough layer of sometimes opaque glaze to be waterproof. Earthenware is more fragile than other types of clay. Earthenware does not have the whiteness and transparency of porcelain, and earthenware products have rather thick, opaque walls of streamlined shapes. Clear lines in the form of faience can not be achieved, so this material is not applicable to the sculptural plastic.
Majolica is a product of pottery clay, which is covered with color glazes – enamels. In the technique of majolica are made as decorative panels, platbands, tiles and much more, and utensils.
Terracotta is a type of red clay, usually without a glaze. It is fired at about 1000 degrees Celsius. The iron in this type of clay, which is used to make these products, gives them a special brown color, which can range from yellowish, orange to red, pinkish or brown
Stoneware is composed of refractory clay and ball clay (kaolinite sedimentary clays), as well as feldspar and silica. It is fired at high temperatures, usually 1148-1316°C (2100-2400°F), and is inherently non-porous. The white, gray or brown clay transforms into a glassy substance during the firing process, which is why the surface of porcelain stoneware products is waterproof. Stoneware can even be used without glazing for storing water, but usually the inside of such vessels is glazed anyway for better preservation and protection against moisture.
Stoneware is much harder, stronger and more durable than ceramics.
Chamotte is a ceramic slaughter mixed with clay. Chamotte has a coarse-grained composition, the glaze on its surface is spreading out in spots, not covering it completely, which gives the product made of chamotte a special originality. It is very appreciated by artists who have introduced it in the field of arts and crafts. Fireproof chamotte is fired at a temperature of 1250 ° C. Such products are not afraid of the cold and temperature changes. However, dampness is not recommended to them. From fireclay ceramics are made garden and interior lamps, bases for fountains, pots with trays, cachepots, animal figures, vases and amphorae.
Porcelain is a white clay used to make functional and non-functional products. In fact, the chemical composition of porcelain is a combination of clay, kaolin (the only clay known to be transparent), feldspar, silica and quartz, but other materials can also be added.
The higher the kaolin clay content, the higher the technical characteristics of the resulting product.
Porcelain is traditionally fired at very high fire temperatures above 1260 ° C (2300 ° F). As in the case of porcelain stoneware, during firing the body turns into glass, which is why the surface is very little porous and does not absorb any liquids. The surface is usually very smooth, even if it is unglazed, and the thinness and plastic properties of the clay used allow the creation of intricate fine details.
The most important defining characteristic of porcelain is its transparency. Porcelain becomes very white and translucent after firing, which allows light to pass through it and reflect it. All other ceramics are opaque and do not allow light to pass through.
Another determining factor is sound. If you lightly tap a porcelain item, it will make a jingling sound like a bell.
Porcelain is a very strong and hard material.
Chinese porcelain
Because of the many difficulties in working with porcelain, several variations have been developed. They appear under the names hard porcelain, soft porcelain, bone china, and are sometimes mistakenly referred to by the generic term china as well.
Fine porcelain
Soft or fine porcelain is fired at a lower temperature than hard porcelain – about 1200 ° (2200 ° F). Fine porcelain is much softer than classic porcelain, making it much more suitable for applications such as plates and cups.
Bone china
Bone china is a type of soft porcelain which is made white, light and translucent by adding calcined animal bone to the porcelain mass. The quality of the final product depends on how much bone is in the mixture: high-quality bone china must contain from 30 to 40-45 percent bone.
Bone from certain animals, namely cattle, gives the fired body a high level of transparency and a unique milky white color.
Bone china cannot be fired at the same high temperatures as classic hard porcelain.
Bone china has a very high mechanical strength and resistance to chipping, which allows for the production of thinner objects, unlike other types of porcelain. However, its glaze is more susceptible to cracking and does not like temperature changes.
Paper clay paperclay is any clay mass to which a treated cellulose fiber (paper or cardboard being the most common) has been added. Sometimes cotton or nylon threads are used. This technique expands the possibilities of clay, a material beloved by all ceramists.
When using paper clay, it became possible to make products of almost any size, gluing individual elements and whole fragments at any angle in a dry form, which cannot be done with ceramic products.
Conclusion
Technically speaking, clay products and ceramic products are one and the same because they are made in the same way in both the forming, firing, glazing and re-firing stages. However, both terms have different subtleties in their meanings.
The word “ceramics” is a more general term that includes earthenware and earthenware, as well as ceramic dentures, ceramic knives, ceramic tiles, etc. In the context of art, pottery is often seen as a high-end, professional-level work that produces fine art objects of decorative value (clay sculptures or decorative plates).
Earthenware includes less elaborate, and more functional objects that serve a purpose in everyday life (like plates, cups, or vases).