Pottery Glossary

The following pottery terms are used all over the world in reference to the process of making ceramics. Some of these terms refer to making techniques, whilst others refer to the process of drying or firing pots. Whilst this glossary isn’t exhaustive, I hope it goes some way to helping those who are just starting out in the craft.

Bisque (Bisc, biscuit, bisqueware, bisque-fired)

The word refers to the process of the first slow firing through which a chemical and physical change takes place, transforming porous clay into a permanent, hard, ceramic item. In this process, water is expelled from clay particles resulting in these particles fusing together to create one piece. When pots are in a state of bisque, they are still absorbant – allowing glazes to adhere to the body of the pot whilst the shape is maintained.

Burnishing

During the process of burnishing, leather hard or bone dry greenware is polished using a smooth object. Each potter has a personal preference of what they will use: some favour pebbles, seaglass or even the back of a spoon, whilst others will use a rubber kidney. This process creates a polished, glossy surface that may be more resistant to water absorption. This means that burnished pots do not always have to be glazed.

Clay body

Claybody refers to the specific type of clay used. There are many different types of clay that are used in ceramics, including but not limited to: stoneware, earthenware and porcelain. When choosing a claybody, be sure to pick one that is suitable for the intended use of the item that you will make.

Coiling

Coiling is an ancient method of handbuilding, consisting of creating sausage-like pieces of clay and joining them together from a solid base to create a pot. This is a flexible way of working as almost any shape can be achieved with a little experience or patience.

Crazing

A glaze defect that is often a result of a difference between the rate of shrinking in the glaze and the claybody. However, sometimes, crazing can be a positive thing. Crackle glazes create an intentional crazing effect, to which Indian ink can be added to highlight the decoration.

Firing

The process that clay goes through in order to create a durable and permanent piece of ceramic. During the firing process, both clay and glaze goes through a chemical change that results in this permanency. Through carefully controlling certain factors, potters can play around and experiment with different firing processes. Ceramic pieces are often fired a few times at different temperatures to create the finished piece.

Food safety

This is an important part of the functional potter’s day to day. Glazes that include lead and other metals should not be used for tableware. This is because even after firing, there is a risk that these ingredients could leach into acidic foods or liquids. Most of today’s potters are aware of this and as a result only use food safe ingredients in glazes for tableware.

Greenware

At this stage of production, a pot is going through the drying process before it is safe to be fired. The term greenware is an umbrella term that refers to pots that have not yet been fired.

Glaze

Glaze is made of chemicals that are ground into fine powders and mixed with water, before being applied to bisqueware. It is possible to create thicker glazes to be brushed on to a piece, or thinner glazes ideal for dipping or pouring. When the glazed piece is exposed to high temperatures it will melt and vitrify, forming a glassy surface that is fused to the ceramic. When buying glazes, you should look for one that matches the claybody that you are using in order to avoid problems like shivering, crazing or pinholing.

Leatherhard

At this stage of production, a pot can safely be handled without it being at risk of warping or deforming. However, the clay can still be shaped or altered at this point – for example, handles can be applied onto leatherhard clay, and slip can be applied.

Pinching

This handbuilding technique involves using the fingers to mould the clay into different forms, working around evenly to create your desired shape.

Raku

Raku is a firing process that originated in Japan. Today, rakuware is mainly used for decorative purposes. When the kiln is still very hot, a pot is removed and transferred to a raku pit that is lined with combustable, organic materials. These materials set on fire and the natural gases and acids in these materials create a variety of unique finishes to the pot.

Shrinkage

This is the irreversible change in size that occurs as pots dry and then when they are fired. Most pieces undergo some level of shrinkage, so potters have to take this into consideration when making.

Slab building

A technique of handbuilding that involves rolling thin slabs of clay that are assembled together or around formers to create shapes.

Slip

Watered down clay that can be mixed with stains. Slips can be applied with brushes as decorations, or can be used almost as a glue to attach handles.

Vitrification

This process is brought about by exposing a pot to high heat. Here, a clay or glaze will go through a chemical change and fuse together. The process of vitrification converts clay (as a soluble material) into insoluble, permanent ceramic.

Wedging

A process of kneading the clay to align clay particles, remove air pockets and homogenise ingredients in the clay. Wedging is particularly important for throwers, but handbuilders will also do this to prepare the clay for working.