Pottery & Ceramics
A brief guide for absolute beginners

Introduction

Pottery, or ceramics, are terms used to describe the process of making things (be them bowls, sculptures, tiles or whatever) from clay and then colouring, glazing and firing (cooking in a kiln) the pieces to create the finished article.

The process is made up of a number of steps, each of which has both artistic and technical elements. Some basic understanding of chemistry is helpful but not necessary.  Many of you reading this will have already had some experience of doing pottery, perhaps at school, and will already know much of this. If so, excellent, If not, I hope that this provides a simple starting point to understand the basics.

The processes documented here are those which I do, and which I teach.

This document is meant to be basic and therefore some aspects have been over-simplified to keep this as concise as possible. It can only outline the steps. It cannot teach you the physical technique and know how. That is what hands on lessons are for.

 I recommend that you familiarise yourself with these basics and then possibly have a look at Youtube videos to see what it actually looks like. I have not made any video tutorials but there are plenty of good ones there to enjoy.

I will explain the core materials and equipment first and then outline the processes in a roughly chronological order.

Core Terminology / Jargon

Clay - The basic raw material
Wedging - The process of preparing the clay and removing air from it
Centering - The process of turning a (kicking and bumping) lump of clay on the wheel into perfectly balanced solid form
Throwing  - The process of creating bowls and other round forms by using a wheel
Turning - (aka trimming) Turning the pot upside down to trim off the excess and make a clean foot ring
Glazes - The ‘paint’ used to decorate the piece (often with a shiny glass-like finish)
Firing - The process of cooking clay pieces at high temperature
Kiln - The high temperature oven
Slip - wet (usually coloured) clay used for decorating pieces before they are fired
Bisqueware - (sometimes called biscuitware) half finished clay. Fired once but not glazed


Materials

Clay

All pottery is made of some sort of clay.
Potters clays (both earthenware and stoneware) are made from very tiny particles of weathered stone (like sand but much finer). The main constituents are silica (the main element in sand) and alumina (aluminium oxide), together with other salts and compounds (such as iron and calcium carbonate) together with water.  Clays are different from mud as they do not contain hydro-carbon based organic materials.

Potters clays can also be dried out and then recycled simply by soaking in water - provided they have not been fired.  Dry clay is very weak and brittle - which is why created pieces need to be fired. The extreme temperatures cause the particles to change their structure and stick hard together, permanently.
For the sake of simplicity, I will set out three basic categories.

1. Low temperature hobby clays.
There are a number of clays available for modelling and sculptural purposes which are designed to harden permanently at room temperature or in a normal kitchen oven at below 400 degrees centigrade.  They are well suited to small sculptures but are not often used by ‘potters’ and I have very little experience with them.
Many of these products are not easily recyclable after they go dry.

2. Earthenware
Earthenware clays can be red (terracotta) or beige or grey in colour. Earthenware clays are usually fired to about 1050 degrees centigrade. They have the advantage of relatively lower temperature firings and  there is a greater range of glaze colours available. The disadvantage is that they are less hard wearing.

3 Stoneware
Stoneware clays are generally light grey, beige or white. They are stronger and more hard wearing then earthenware and therefore suitable for every day use and dishwashers. the downside is they require higher temperature. Stoneware is typically fired at about 1250 degrees. Due to the higher temperature there are less glaze colour options, and the colours are often less vivid.  Porcelain is a type of stoneware, characterised by its pure white colour.

Note - Mixing stoneware and earthenware together should be avoided.  Earthenware will simply melt at anything over 1150 and stoneware will not go properly hard unless it goes up to 1200.  I teach using stoneware.

Glaze

Most pottery items are finished with a coating of glaze. Think of it as a fine varnish layer of glass which is made to stick to the pot like a paint.

Glazes can be gloss or matt and they can be transparent or opaque, white or coloured. Glazes are normally applied as a watered down emulsion. They can be applied by dipping the bowl into a bucket, or sprayed on, or painted on. Like clays, glazes consist of silica and alumina, but they also contain other chemicals (called fluxes) which, when fired to high temperature, make the silica melt into glass.

Glazes can be purchased as powders (ready to be mixed with water) or as tubs of liquids. Many professional potters like to explore the chemistry aspect and mix up their own special glazes from raw materials.

Glazes are not however like a normal paint. Before they are fired they are more like children's powder paints, do not 'set' and will wash off. Glazed bowls do need to be fired, at high temperatures.

Oxides and Stains

The colours in pottery come mainly from metal oxides, chemical salts and a number of (specially made) stains. These come in the form of powders. These can be mixed with water and painted on underneath a transparent glaze (underglaze) or can be pained on top, or mixed in with the glaze to add colour. Generally speaking, the raw colour (of oxides and glazes also) is not reflective of the final fired colour.  For example, Cobalt carbonate is pink in its raw form but will become a vivid blue when fired. 

Slip

Slip is the term given to runny wet clay which can be applied for decorative purposes. Wet clay can be coloured and can be applied (painted or dripped over the piece) in various patterns for interesting effects.


Equipment

Potters Wheel - An electric or kick-powered horizontal spinning wheel, with adjustable speed and a flat metal head
Kiln - A high temperature oven. Kiln furniture refers to the shelves and props inside it
Wedging Bench -A strong an sturdy table is required for preparing the clay before use
Banding Wheel - A small, not-motorised. hand wheel. Useful for decorating and glazing
Bat - Plywood or plastic disc on which work in progress is placed. A piece can be thrown directly on a bat - provided the bat is suitably attached to the wheel head.
Sponges - Small pieces of sponge used to apply water during the throwing process
Turning and Trimming tools - Used to shape a piece and cut away excess clay
Wire - Used mainly for removing a piece from its bat
Buckets, scrapers, cellophane bags - and possibly a few other minor bits and pieces.


The Core Process

This outlines the steps in the process of making a bowl on an electric wheel using earthenware or stoneware clay.

1. Preparing the Clay - Wedging

Before a piece can be made the clay must be of the right even consistency (wetness) and must be free from any air bubbles. (Air will expand at high temperature and any bubbles would ruin the piece).  The process of warming up the clay and removing air bubbles is called wedging. It involves creating a lump of clay to the desired size (or weight) and then using both hands to push down into the clay and then roll it back partially before repeating the process again and again (about 80 times). It looks a bit like kneading bread (except that kneading puts air it while wedging takes it out). At the end of the process you will have a nice round ball of clay. I use a technique called 'bull's head' wedging.

2.  Centering

Tricky and absolutely essential. Centering is the process of sticking the ball-like lump of clay to the wheelhead and then working it up and down until you have a perfectly centered ‘beehive’ shape which revolves perfectly evenly and with no lateral movement (kicking).  This can be a difficult and frustrating art to master, especially for larger pieces. The process involves a repeated process of squeezing the ball of clay into a cylinder, sometimes forcing it up, before pushing it back down. The process requires the potter to hold a solid frame with the elbows supported by the thighs. There are techniques and tricks which need to be learned and practised. Failure to properly center the clay will make throwing almost impossible.

3  Throwing

For me, the most interesting part when you turn the solid ‘beehive’ cylinder into a beautiful bowl (or vase etc). It starts with pushing the thumbs down through the middle to create the rudimentary hollow cylinder form - making sure that you don’t push down too far (or you will end up with a flowerpot !). Making the shape is all about pinching the clay from the bottom and then sliding it up the sides and adding it to the top of the walls.  One finger inside and the other on the outside, in parallel and slowly.

As you keep repeating the process, the wall gets higher and begins to thin out. It is not about squeezing the walls. For beginners, it is important to start by learning how to throw a clean vertical cylinder. Then you can learn how to use the difference in finger height to change the form from a cylinder to a bowl. The techniques require slow wheel speed, a solid frame, and steady concentration. It will seem really slow at first but as you get better you will get a bit quicker too. Body posture and hand positions are very important.

Note - for my classes I use a system called ‘Bat-Retainer’ which allows for each piece to be thrown directly on a bat which can then easily be lifted off the wheelhead (with the piece still attached). This avoids the awkward process of wiring through the bottom of a piece and having to slide it off the wheelhead and then on to a bat - which often causes a bowl to become warped or skewed.

4  Turning

Also known as trimming. This is where the part dried (‘leather’ hard) piece is turned upside down and put back on the wheel head. The purpose is to cut away the excess clay from the bottom (foot) of the bowl to make a lighter bowl with a more attractive base or foot ring. First you need to centre the upside down piece on the wheel head and use little pieces of clay to hold it in place. Then, while the wheel spins, you use carving tools (usually wire loops on the end of a wooden handle) to carve away the excess - much like using a lathe.

Having a good well defined foot ring will make the piece more aesthetically pleasing and will also be helpful when it comes to glazing. It is also very important to ensure that the base of the pot is not too thick, as this can sometimes lead to cracking.

5  Drying

Before the piece gets fired and/or glazed it needs time to dry out fully. This takes days ! Before it dries, you have the opportunity to apply slip to make a design or pattern. You also have the chance to imprint or carve a design. Remember that the piece must be totally dry before it gets fired. Any water left in it would expand dramatically when it reaches boiling point and the explosion would break the piece.

6.  Biscuit firing

Also, and more correctly, known as Bisque firing is when the piece is fired to about 80% of the final temperature. For earthenware that is 800 instead of 1050 and for stoneware its 1000 instead of 1250.  Firing is a lengthy process taking several hours to get up to temperature and even more to cool back down again. The reason for bisque firing is to best prepare the piece to correctly absorb the coat of glaze. - before final firing.  Applying glaze to unfired clay is possible but there is greater risk of the glaze not sticking correctly or of it causing cracks to the finished product.

Unglazed pots can be stacked on top of each other for bisque firings as there is no risk of sticking.

A kiln is a potentially dangerous piece of equipment. It consists of a chamber made from special bricks and running on the inside next to these are electrical elements like the coils in an old fashioned bar heater (there are also gas kilns). The machine has a programming unit which allows one to set the maximum temperature and the rate of temperature climb. The controller will switch the kiln off when it reaches its maximum temperature.  A kiln uses a lot of electricity and gets extremely hot inside. The outside is still quite hot and the areas around a kiln must be kept absolutely clear of combustible materials. It is also not advisable to spend too much time in the close vicinity of a kiln when at high temperature. For these reasons I do not allow students to use the kiln themselves and I will do firings outside of lessons.

7.  Glazing

Finally, the fun part of decorating the piece by painting, dipping or pouring on glazes.  I have lots of different glaze colours to choose from. Most are brush on glazes in ready mixed tubs. I also have several stain and oxide powders and a smaller selection of buckets of glaze mixed up for dipping.

Personally (although it takes longer than dipping) I like to apply brush on glazes, painting on about 5 or 6 coats (depending on consistency) and sometimes using different glaze layers so as to get chaotic reactions between the glazes - leading to swirling or stripy patterns. The results are not always predictable but are usually interesting and unusual.

It is important to make sure that there is not too much glaze on a piece, especially on the outside at the bottom. Excess glaze will run down the side of the bowl. Glaze on the foot of the bowl could cause it to stick to the kiln shelf.  Thereby ruining both the bowl and the kiln shelf.  If the glaze is too thin it will look streaky and patchy.

8.  Final Firing

Once glazed, and left for a day to dry out, the piece can be fired up to full temperature. Then, once it has cooled back down, it is ready to be used and enjoyed.

In final firing, only a few pieces can be fired together. Pieces cannot touch each other in a glaze firing as the glaze will act like a glue - causing them to stick hard to each other.

Pieces can be re-fired if the glaze was too thin, but this can be tricky as it is difficult to get raw glazes to stick to a finished glaze surface.


Other Points to Note

Pottery is messy !  The materials do mostly wash out - but don’t do it in your best clothes. A kitchen apron will be provided but bring scruffy clothes that you will not mind getting dirty.

It takes time. From start to finish, a bowl will take between 10 days and 2 weeks (mostly due to drying out and firing times)

It can seem frustrating at first. Centering especially can sometimes be a right pain - but you will get better with practice. The 'key' is to learn how to develop the correct postures, body-frames and hand positions.

Throwing techniques do require fingertip control and are therefore not suited to long fingernails.

In the end it is rewarding and it feels good when you have individual items which you know you made yourself.



Written by Andrew Richardson
Bristol Based Pottery Teacher
37 Cromwell Road
Bristol BS6 5HD
Tel 07817 509 452
ahr@ukfsn.org
www.ahr.me.uk
www.bristolpotteryclasses.com