Everything you needed to Know about Ceramics but were afraid to ask!
One of the major ingredients in some clays is a chemical known as Kaolin that was used for stomach aliments (the main ingredients in most clays are silica and alumina). Modern world, you may know it as the product Kaopeptate. Prior to the 4th millennium BC, all ceramics were made by hand, especially by way of coiling. This is rolling clay snakes or coils out (like ropes), then stacking them one on top of the other to finally smooth over the coils (where the coils meet) together, eradicating the joints between coils. Sometime during the 4th century BC, the potter’s wheel was invented in the coastal region of northern China. Potter’s wheel is basically a rotating disk, which provides the momentum while a lump of clay that is centered on the disk is manipulated. The forms that are made from the wheel vary, but most of the objects are round in shape, such as bowls and vases.
In parts of Turkey and the Middle East, some of the wheel designs that were created in the time of Christ are still being used to this day. Molding also developed in Neolithic times. Wet clay was pressed against a mold, made solid, and then withdrawn from the mold. This made elaborate shapes and complex decorations possible. As the years went by, molds were made out of many different material (mostly wood and plaster). Clay is fired at different temperatures depending on the chemical composition of the clay. There are three basic types of clay bodies: Earthenware, Stoneware, and Porcelain. Earthenware is considered a low fire type clay which is porous and permeable. (fired between 600c to 1,100c). Stoneware and porcelain are high fired and the body fuses, becoming impermeable and extremely dense (stoneware fires between 1,200c to 1,300c, while Porcelain can fire up to 1,400c).
During the Middle Ages, it was Asia (mostly Korea, China and Japan) that had Porcelain and used this white clay body to their advantage B having such a white, translucent body was much revered and all of Europe was jealous of such fine materials. Porcelain was a major export item and China’s detailed plates using cobalt (blue) and red oxides were the talk of Europe. Porcelain because of it’s high failure rate (more breakage when using the clay body when it dries and fires) is still highly revered. Clay is used in our mouths (porcelain fillings) and in space (silicon-based ceramic tiles on the space shuttle). It’ not just for keeping your coffee warm anymore. Pretty impressive for a little pile of mud, huh?
There are numerous forming methods that are used. Some of them are: coiling, slab building, throwing, jiggering (which is very similar to wheel throwing) and casting. Coiling is taking clay and rolling it into little “snakes” or rope “coils” which are then put into the desired shape, and then smoothed together. Some of the earliest pottery found was made in this manner.
Slab building is rolling out a piece of clay flat, like a piece of paper (except not that thin) and then using. A jigger has a wheel head that spins a mound of clay around, and another device that is used in conjunction with the rotating wheel head that is a mold. The mold is pressed against the spinning clay and it cuts away the excess, making it easy to duplicate shapes.
Casting is using molds (normally plaster) and a watered-down clay mixture called slip is poured into the mold. Once it is dry enough to move without damaging it, it is pulled out of the mold and allowed to dry completely, then it is fired.
There are three stages of ceramics: greenware, bisque, and glazeware. Greenware is an unfired, formed piece. Bisque means “half baked”, which is basically a piece that has been fired to a temperature which turns it hard enough to glaze but not too hard so that the piece’s pores close (you need them open in order for the wet glaze to hold firm to the surface). Pieces should be bisque fired before glazing to avoid blow ups or glaze discoloration. Some pieces, such as flowerpots, are not glazed – you don’t have to glaze pieces if you don’t want to.
To make a piece sanitary (i.e. able to eat food off of) one needs to glaze the piece in question. Glazeware is when a bisqued piece has been glazed and fired. A glaze is a mixture of chemicals, mostly silica (which is the major component of glass), clay, a melting agent, water, colorants and a suspension agent (which allows the chemicals to stick together and not separate like oil and water). Depending on the chemical composition of a glaze, when it fires against a bisqued piece, the glaze will turn glass like and in high fire glazes, will merge with the vitrious clay. There are various types of glazes and items to help decorate: opaque, translucent, semi-opaque, over glazes, under glazes, engobes (a slip that has been colored with stains or oxides, used on greenware), metallics, lusters, high fire, low fire, matt and glossy. Some glazes work well with each other, while others need to be used by itself.
Glazes are brushed on, pieces are dipped into glazes, or the glaze is poured across them. There is also spraying (basically a special air brush). As with painting and dying clothing, wax is used as a resist technique, so whatever the wax touches, the glaze will not stick to it. Clay is a great medium with hundreds of possibilities for forms and decorations.
Let’s now go into more details on how that effects your persona and life in the middle ages. The majority of the people that lived in the middle ages did not have a whole lot of money. Keeping this in mind, clay was an inexpensive material that could replace many of the expensive metal items and lasted longer (and was far more sanitary) than wood products. In Asia especially, ceramics were used everywhere, from temples to the farmer’s dinning table. “The Way of Tea” was an honored ritual, which focused around tea and its presentation. Korea, China and Japan were instrumental in the development of porcelain. For this ceremony, the tea bowl was a specific design, with each section of it done just so. At the end of our middle ages (late 1500) a potter in Japan accidentally stumbled upon a new glazing technique called Raku, which was used exclusively for “The Way of Tea” and the emperor of that time honored the potter. Only in the past 80 years did Raku come to America (brought to Great Britain first by a potter named Bernard Leach) and there is still a “Mr. Raku” in Japan, 15th generation of the first potter, making tea bowls.
In Europe, however, they were using earthenware. Remember that porcelain is a white, dense clay which was higher fire, in comparison to the porous, lower fire earthenware (whose colors range from beige to brown). Earlier in period, the Romans and Greeks used a decoration technique called Terra Sigillata, which was a refined slip (extremely strained clay that was skimmed for the purest deposits) that was brushed across an unfired vase, burnished (or naturally burnished by nature), fired and glazed. Later, when Tang Dynasty ware was extremely popular, a technique was developed in Mesopotamia between the 9th and 10th centuries called Maiolica (sometimes referred to Majolica, Delftware, or Faience) which earthenware is taken, formed and fired, and a white, thick low fire glaze is applied. Then, stains or oxides (which are pigments that are used to add color) are painted across the white glaze. Once it is fired, the oxides and the base glaze melds on the earthenware, making it look like a porcelain piece with colorants brushed across it.
The general populace could afford these pieces and most middle class had dishes that were made from this technique. These pots were traded heavily throughout Europe and the Middle East. Egypt used to use bisqued pots, fill them with water and leave them in rooms to cool the temperatures down in their dwellings. Some of their famous jewelry they wore was a bluish clay that was called “Egyptian Paste” which was formed into beads, figurines, bangles and inlay. The clay had several chemicals within it, that when it was fired (low temperatures) a blue glaze would form on the outside of the object. When the French first started their explorations of Egypt years ago, when they found these beads, they first called in Faience because the color was so similar to the Faience-ware that Italy made in the 1300’s.
So, depending on where your persona is from, they may have went to a temple that was decorated from the ground up with brilliantly glazed tiles or perhaps they had a tea set of cobalt across white porcelain. Perhaps they were traders or drank ale from an earthenware jug that a monk in a Monastery used. No matter what they did, they probably used clay in one way or the other, just as we do still today.
Books Used for This Article: “Pottery Decoration” by Thomas Shafer “The Craft and Art of Clay” by Susan Peterson. “Maiolica, Delft and Faience” by Giuseppe Scavizzi Websites: The Raku Museum in Japan: http://www.raku-yaki.or.jp/