Pottery Making

The throwing rib is a very important potter's tool. Usually a smooth flat piece of  hardwood fitting in the hand with one curved and one straight edge, both sharply finished. It is used, along with the fingers and knuckle, to pull-up clay when forming the cylinder, for trimming, smoothing and much else besides. When sharpened it is an effective tool for turning the pot.
A sponge, sheep's wool wadding or a bit of rag can be useful in removing collected water inside the thrown vessel. A knife or cord made of gut may be needed to remove vessels from the wheel head. There is no limit to the ad hoc small tools which individual potters may find useful. A rib- simple and complex rim forms can often be formed  and duplicated with accuracy by the fingers alone, and by a little trimming with a rib.

Pottery throwing

The fundamentals of pottery throwing probably have not changed greatly over the centuries. There are three basic methods:
Pottery can be thrown from a ball of clay placed on the center of the wheel head and then centered to a perfectly symmetrical lump before throwing into shape. This is probably the most common method of throwing. Alternatively, the clay may be centered on a 'bat', a removable wheel head which enables the thrown pot to be removed from the wheel for drying and perhaps subsequent replacement for trimming and turning.
Vessels can be thrown 'from the lump'.  A large cone of clay is centered on the wheel and clay is drawn-up from the cone to form successive individual pots which are then cut off the lump. This method allows the rapid production of small pieces but is less appropriate  for making large jugs.
'Coil and throw' techniques are proper for very large jugs, jars and containers. The bottom of the vessel is beaten-out on the wheel head and the position of the lower walls formed by a large circular sausage of clay, which is then thrown up as far as it will go. A second clay sausage is added, thumbed down onto the walls and then thrown up as before, until the desired height is reached or a further sausage applied. Objects made in this way are a mixture of hand forming and throwing.

The next step in making pottery is the dehydration process in which clay is heated and the water found naturally in it is removed, causes an irreversible transformation - the clay is not simply dehydrated but it become a different product all together. When clay is heated in excess of 500 degrees centigrade another reaction occurs causing permanent and irreversible change. This degree of heating causes the water of hydration to be "driven off". Most often, clays are tempered in the process of pottery making. Tempering is a process in which materials are added to the clay to help the product resist cracking in the final stages of ceramic production. Various materials may be used in the tempering process including shell, sand and pieces of old pottery. The choice of material in the tempering process is often helpful to archaeologists as it is usually culturally based and easily identifiable.

The new product is ceramics, which are unchanged by the presence of water because of absence of water of plasticity. Water of plasticity is the substance that allows for clay to be wetted and dried over and over again without permanent change.

Decoration and pottery shape are very specific to culture. It is easy to determine one time period or culture from another by specific patterns or handles found on the respective ceramics.