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Frequently Asked Questions

If you can't find an answer here, email us and we'll try to help

An extensive source of answers to pottery questions is Wikipedia.

• General pottery questions
• What is the difference between pottery and ceramics?
• How is pottery made?
• What are the different types of pottery?
• What is Raku?
• What is Majolica?
• Where can I buy craft pottery in Auckland?
• Why has the surface of my pot developed a network of cracks?
• What are "reduction" and "oxidation"?
• Are glazes on studio pottery poisonous?
• Questions about the ASP
• What is the meaning of the ASP logo?
• How can I join the ASP?
• Who owns the ASP?
• How long will it take for me to learn pottery?
• Does the ASP have classes for children?
• Can the ASP mend my old vase/favourite coffee mug?
• Can the ASP recommend someone to make a new lid for my broken casserole?

General pottery questions

What is the difference between pottery and ceramics?

Strictly speaking, there is none. Both terms refer to articles made out of clay. Some potters would rather call themselves "ceramicists" or "ceramic artists", but in the view of many this is an artificial distinction that tries to distinguish "artists" from mere "clay workers".

In the wild and woolly 1980s, somebody had the bright idea of providing unfired pieces of pottery for people to decorate and fire. Whoever originated the idea was a genius, as it meant you could charge people at every step of the process: for the raw pots, for the classes where you did the decoration, for the glaze materials and finally for the firing. This was marketed as "hobby ceramics", but as happens, the term eventually got shortened to "ceramics", and this is what most non-potters have in mind when they use this word. Any resemblance between "hobby ceramics" and real pottery is completely accidental.

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How is pottery made?

This topic could have an entire website all to itself, but fundamentally, there are 4 stages in making pottery.

• The raw clay (which may have come in a bag from a manufacturer, be mixed up from the basic minerals, or just dug out of the ground), is formed into a shape.
• Once it is dry, when it is known as "greenware", it is fired for the first time, usually to a temperature of around 1000°C.
• The once-fired ware, now called "biscuit" or "bisque", has decoration applied to it in the form of a glaze, which is water containing suspended minerals and oxides.
• The decorated biscuit ware is fired a second time to the appropriate temperature for the clay. (see earthenware, stoneware, porcelain). This final firing matures the clay and melts the glaze which fuses to the clay body, making it waterproof (usually) and stronger.

There are many many variations on these processes, but they all more or less reduce to the above list in the end.

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What are the different types of pottery?

Another big topic, but pottery can be divided (very) broadly into 3 categories:

• Earthenware. This refers to pottery fired to a final temperature of less than about 1100°C. It is usually somewhat porous, and is frequently, though not necessarily, made of a reddish clay ("terra-cotta".)
• Stoneware. Pottery fired to a temperature of more than 1250°C. This pottery is usually waterproof.
• Porcelain. Pottery fired to a temperature of at least 1300°C, and made of a pure white clay. True porcelain is very hard, and capable of being made so thinly that it is translucent.

It is important when making and firing pottery to know what clay you are using. To see what happens when a low-temperature clay is put into a high-temperature firing, watch this video.

There are many other terms in use that refer to the method of firing (see "raku") or the method of decoration (see "majolica"), but they all fit more or less into the above categories.

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What are "reduction" and "oxidation"?

In pottery terms, these both refer to processes that occur during firing.

Burning - which is what happens during a pottery firing - requires oxygen. Normally the oxygen is taken from the air that is entering the kiln. When this happens the firing is oxidising. If the air flow is restricted, either accidentally or deliberately, the oxygen for combustion is taken from the pots that are in the kiln - from the clay body and from the glazes. This is reduction.
The degree to which a firing is oxidised or reduced can have a dramatic effect on the final appearance of the pots. Some glazes look relatively unchanged, but others can be totally spoiled if the wrong atmosphere exists in the kiln at crucial points of the firing.

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What is Raku?

Rakuyaki or Raku is a form of Japanese pottery characterized by low firing temperatures (resulting in a fairly porous body), lead glazes, and the removal of pieces from the kiln while still glowing hot. In the traditional Japanese firing process, the pot is removed from the hot kiln and put directly into water or allowed to cool in the open air. Raku is considered the traditional method for creating bowls for the Japanese tea ceremony. Raku tea bowls are hand-made from earthenware, each with a unique shape and style. Raku techniques have been adopted and modified by contemporary potters worldwide.
Source: Wikipedia

In New Zealand, Raku ware is often characterised by a black body colour, produced by burying the red-hot piece in dampened organic material such as sawdust, wood shavings or shredded paper, and covering the container to exclude air. This results in the material carbonising and fusing to the clay body, giving the black colour. While Raku is a serious branch of pottery, Raku firings are frequently quite social occasions, as it is possible to go from cold biscuit ware to a completed piece in less than 30 minutes, allowing many people to produce finished work in the course of an afternoon.

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What is Majolica?

Also known as "maiolica" or "faience"

See these two references:
Majolica.net (Aesthetics warning - this site is somewhat style-challenged)
Wikipedia

It is also used as a generic term for modern earthenware pottery with a white glaze and colourful decoration.

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Where can I buy craft pottery in Auckland?

Try these places.

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How long does it take to make a piece of pottery?

If you ask any potter this question, there will be a suppressed sigh and a deep breath, as it is almost impossible to answer.
Take a coffee mug:

• Making it on the wheel - maybe 1 minute.
• Finishing the base once it has dried slightly - another minute.
• Putting on a handle - another 30 seconds.
• Biscuit firing the mug in conjunction with lots of other pots - maybe 4-5 hours.
• Glazing the mug - another 30 seconds.
• Firing to the finished temperature, also with many other pots - another 5-8 hours.
• But mixed in with all that there is:
  • Preparing the clay.
  • Letting the work dry.
  • Preparing glazes.
  • etc. etc.

So how do you get a time for one mug out of all that?

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Why has the surface of my pot developed a network of cracks?

When the glazed surface of a pot develops a large or small network of cracks it is called "crackle" (when the potter intended for it to happen) and "crazing" or "#@!!$##" (when it is unintentional).

It is caused by the fact that during firing, the clay body of the pot and the glaze on the surface expand and contract by different amounts. If the glaze finally shrinks more than the pot the glaze is under tension, and will sooner or later develop cracks as the tension is relieved. Glazes cope much better with a small amount of compression, and produce a smooth surface on the finished work, so this is usually what a potter aims for when choosing a glaze for a particular pot, especially if it is domestic ware intended to be used for food. However crackle glazes can look very beautiful on decorative pots, and potters will sometimes strive for the effect.

Over a long period of time, the body of a pot can absorb moisture, which causes it to swell slightly. This will also put the glaze under tension, which is why old pottery frequently shows signs of crazing.

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Are glazes on studio pottery poisonous?

The short answer to this is - in general, in modern pottery, no they are not.

An exception to this would be some low-fired decorative pottery such as raku, where the a few of the glazes used might be injurious if the works were to be used as drinking vessels. However raku pottery is in general purely decorative, so the issue should not arise.

Modern pottery glazes are formulated so that any materials that are toxic in their raw form are chemically locked up in the glaze in such a way that they cannot escape.

In older times, lead was frequently used in pottery glazes to give a high gloss to the glaze and to lower the maturing temperature. Unfortunately the way in which it was used meant that (a) the pottery workers were very vulnerable to lead poisoning and (b) the finished pots could release lead from the glazes, especially if they came into contact with acidic liquids. This is no longer the case. If you see a piece of modern pottery described as having a "lead glaze" (unlikely), it is worth asking questions about the glaze, but is almost certain that the lead will have been incorporated in a non-toxic form.

For a discussion on the toxicity of raw glaze materials, see this website.

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Questions about ASP

What is the meaning of the ASP logo?

See this page.

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How can I join the ASP?

Go to this page and click on the link in the sidebar.

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Who owns the ASP?

The ASP is an Incorporated Society consisting of over 300 members. So it is "owned" by its members.

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How long will it take for me to learn pottery?

The short answer is 5 minutes, the long answer is a lifetime!

If you take a small lump of clay and form it with your hands into a cup shape, you have learned basic pottery. Anything else is just refinement. However if you want more than that, a class at ASP will set you on your way. Our 10-week morning or evening classes cater for all levels of experience, from absolute beginner onward. After one term, you should be getting a good set of basic techniques.   Caveat: Everyone is different, so this cannot be taken as a guarantee that ASP will turn you into a potter after one term!
Practice is hugely important - the more you do, the better you get. As a student or full member of ASP, you are entitled to use our studio facilities outside class hours.

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Does the ASP have classes for children?

Much as we would like to, the answer is no. Our facilities and timetable are fully stretched with offering classes for adults. These places do have children's classes - try there.

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Can the ASP mend my old vase/favourite coffee mug?

Sorry, no. Ceramic repair is a specialised skill. If you want to try it yourself, Araldite or superglue can sometimes work. Wrightway Studios in Auckland are specialist restorers.
This is not an endorsement. ASP has no knowledge of Wrightway's skills and experience.

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Can the ASP recommend someone to make a new lid for my broken casserole?

We can try, but your chances of success are quite low. Unless you can be sure of the original clay, what temperature it was fired at, exactly what glaze was used, etc. etc., you are most unlikely to be able to get a perfect match. Your best chance is if you know who originally made the pot.

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