Top ten tips on pottery firing

Pottery making provides some challenges for the beginner but non more so than at the firing stage. No-one wants to lose their precious ware after making it so lovingly. It is quite usual for small studio and craft potters to use intermittent box type kilns to fire their ware. Whether you use gas or electric as the energy source the principle is the same; heating an enclosed space containing shelves of pottery. Whilst the science of firing is quite complex and often outside the knowledge of many hobby potters most know it is important to follow some basic rules. The following tips are aimed at giving you the best performance from your kiln whatever the type.

1. Temperature uniformity is key to achieving consistent results. This should be the aim when firing your kiln.
2. Measure the performance of your kiln using bullers rings or Orton cones. Control it using an electronic temperature controller.
3. Record firing cycles used and settings for each firing as well as Bullers Ring or Orton Cone values.
4. Measure and record the gas or electricity used in KWH for each firing. The trends in this often give you a pre-warning of catastrophic failure.
5. Regularly calibrate thermocouples as they deteriorate over time.
6. Inspect refractory brick or lining regularly to ensure large cracks are not present. Remember large cracks in brickwork will affect kiln temperature uniformity.
7. Inspect electric elements regularly as over time they become brittle and may distort or break.
8. For gas users the colour of the flame is a guide to the kiln atmosphere. Yellow flame is reducing while blue flame is oxidising.
9. Placing ware affects the firing performance of the kiln. Large or thick walled pieces require more heat and act as a heat sink.
10. Don't be greedy- firing pottery too fast can lead to all manner of faults. Unless the glaze and body are designed to be fast fired don't do it!

More information and other technical articles on pottery and ceramics can be found at my website The Potters Friend.

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Inspirational pottery glazes

The special ceramic materials and process

Reactive coloured glazes

The first article of my series on glaze making identified the basic ingredients used in glazes as silica, felspar, frit, and clay and explained how a little science would help speed up your artistic flair!.This second of the series on glaze making discusses the non core ingredients of a glaze and explains how a little science in the form of good processing can ensure that you achieve the best result from your glaze making efforts.

The 3 Basic Questions

To make truly inspirational glazes we need to establish at least 3 things

1) What type of glaze we want to make?

2) What type of body it will be applied to? Stoneware?, Earthenware? Biscuit? Clay?

3) What firing temperature/cycle do we intend to use?

Once we have the answers to these questions we can begin to formulate the glaze.

The choice of non core glaze materials

Making a silky matt -what to add to your basic glaze

Silky Matt glaze

Let us assume we want to make a white silky matt textured glaze firing at 1150C on stoneware biscuit.

We have already identified silica, felspar, clay and frit as core glaze materials. This means that at least 2 of these materials are used in almost all glazes.

Using the same cake making analogy as before, these ingredients are considered the eggs, butter, flour and sugar equivalents of the glaze recipe!

The materials we might consider adding to these core materials could be:-

Limestone (calcium carbonate)

Needle-like crystals on glaze surface

Dolomite (calcium magnesium carbonate)

Zinc oxide

Alumina (aluminium oxide)

wollastonite (calcium silicate)

clay (alumino silicate)

These materials help to form crystals on the surface of the glaze on firing and thereby help create the matt (dull) texture. However these materials also influence how the glaze melts and bonds to the body on firing. It is an absolute necessity to match the glaze to the clay body or on cooling the glaze may just flake way like old paint! (Technically the glaze and body thermal expansion need to match so that the glaze is in compression after firing.) But lets not go too deeply into how we do that at this stage.

Alumina does not readily melt at this temperature so the likely (and easier) materials to use are zinc oxide, limestone, dolomite and wollastonite. Adding these materials in the right proportions to make a suitable glaze takes a lot of trial and error.

Developing the Glaze Recipe

If you start a with a basic 1250 C recipe as follows:

Base Glaze

Silica 38

Felspar 40

Clay 10

Limestone 12

and start replacing the silica and felspar with more fluxing ingredients that create crystals and allow you to fire at a lower temperature you might eventually reach a formula

Modified Glaze

Limestone 12

Dolomite 25

Felspar 20

Clay 25

Zinc oxide 4

Boron frit 9

Silica 5

Imagine how many test glazes you might need to make before arriving at such a detailed recipe? Note how different this is from the starting base transparent glaze! The material recipe is not the only part to consider when making glaze. The particle size of the glaze materials needs to be reduced to a fine powder by grinding with ceramic pebbles in water to less than 75 microns. Often, for best results, the mean particle size needs to be closer to 15 microns-the diameter of the finest human hair. This allows the glaze particles to react and melt during the firing process.

Firing the Glaze

The firing process is equally important in obtaining satisfactory and repeatable glaze results. Initially the firing cycle should remain constant as you develop your glaze recipe. A typical glaze cycle might be 150 C per hour ramp from room temperature to the peak at 1150 C, followed by a holding period (soak) at peak temperature of 1 hour, followed by kiln switch off and natural cool to room temperature.

Note that the cooling is often as important as the heating process when firing matt or crystal type glazes.

Clearly making glazes is quite a complex process. However, like the best potters, in time you will come to believe that this is what makes pottery glazing so interesting. You can never be sure what will come out of the kiln each day!

In the next of the series the use of ceramic colouring pigments to create even more interesting coloured pieces will be examined..

Pottery books of value

A great way of backing up your knowledge is to read some simple pottery making books. Some of the best books are those you keep going back to as your knowledge grows!

Thought for the Day

In pottery making it rarely goes exactly as you would like first time. Stay positive! Use it as a learning experience.

Henry Ford Quote:

"Failure is only the opportunity to begin again, only this time more wisely."

~ Henry Ford

Happy Potting
The potters Friend

More information and other technical articles on pottery and ceramics can be found at my website The Potters Friend. Go now to sign up for my free newsletter.

The Wedgwood Collection and the changing face of UK pottery

Wedgwood Museum

Staffordshire pottery manufacture changed forever in the late 1980's and early 1990's. The power of the supermarket buyers, the draw of low cost manufacture overseas and the changing markets in Europe all contributed to the massive decline in pottery manufacture in the UK. So many big names like Royal Doulton, Spode, and Royal Worcester, to name but a few, now exist merely as brands with the factories closed and demolished. Bleak as it was for the thousands of workers who lost their jobs during that time, many of those workers still talk fondly of the friendships, skills and pride of working in the hundreds of potbanks which existed at that time in north Staffordshire and especially Stoke on Trent.

Staffordshire Oatcakes

It was not just  the potteries that demised but also the services to those factories, the engineers, the material suppliers and sandwich and oatcake shops that provided breakfast and lunch to the hungry workers at break times.For the lucky few they found work elsewhere and the humble Staffordshire Oatcake lives on mainly through online marketing and Social Media.

Many of those pottery workers now rely heavily on their work pensions created during their employment at companies like Wedgwood. However Wedgwood pension trust has a big pension deficit that is causing  problems.

Over the last few years the importance of this pension deficit has been highlighted as the struggle to keep the magnificent Wedgwood Collection at its home in the Wedgwood museum in Stoke on Trent continues.

For those who have not seen the collection I urge you to do so. You will not be disappointed. At over 80,000 historical pieces, ranging from early experiments for new bodies and glazes through to modern production as well as rare manuscripts and letters, pattern books, works of art and photographs, covering the 250-year Wedgwood history, it is one of the most unique industrial archives in the world. The importance of the collection is explained in more detail in this Wedgwood video link.

The collection is under threat because a legal loophole allowed a Wedgwood previously in liquidation to place pension debt in the Museum trust. The trustees have no option but to try to pay off this debt by selling some or all of the collection.

We cannot lose this collection from the UK or allow it to be dispersed around the world to private collectors. It is OUR heritage and I urge you to donate to help meet the £2.74m shortfall still required to keep the collection together in the UK.

Thank you for your support.

How to Choose Your Pottery Clay Body

What is clay?

Flat plates of clay particles

Before choosing your pottery clay body it is first important to understand a little about clay and why it is used as a component of a clay body. Clay is a mineral extracted from the ground which can be readily moulded like plasticine. At microscopic level, the particles of clay have a flat plate-like structure giving them this plastic like property. The 2 most commonly used pottery clays are Ball Clay and China Clay (Kaolin). Ball clay tends to be very plastic-mouldable but off white in colour. China clay is less plastic but has a whiter fired colour. Many other clays are available but they tend to be off white to red in colour and therefore less used in high volume white pottery manufacture.

What is a clay body?

The terms clay and body are used by potters almost interchangeably. However in most cases it is not technically correct! In simple terms a body is a formula containing clay and other minerals. Therefore clay is a raw material component of a body. In past times a body was simply a clay dug from the ground which was variable in both its composition and properties. However, modern commercial potters no longer rely on bodies manufactured from clay alone. To achieve specific properties they are scientifically formulated in a very precise way. A wide range of raw clays and minerals are used from all around the world. They vary in colour, strength, particle size as well as mineralogy and purity. No two clays from different parts of the world are precisely the same although for comparison purposes they can act in a similar way when used as part of a body formula. For studio pottery manufacture coarse minerals called grogs are often added to the clay body formulas to give additional texture appeal and improved properties.

How to choose the best clay for you

Firing range of your kiln

The maximum firing temperature of your kiln should be your first consideration when deciding which type of clay body to buy. It is no use choosing a stoneware clay firing 1250 C if your kiln will only fire to 1200 C. Lower temperature kilns are suitable for earthenware and terracotta bodies (less than 1200 C) whereas high temperature kilns are acceptable for most bodies including porcelain and stoneware.

Colour

The fired colour of the body will often dictate the cost. In general whiter clay bodies are more expensive than buff or cream coloured ones. The type of clay body you use is often prescribed by your colour selection. For example porcelain and bone china are always very white after firing.  To give you an idea of the fired colour produced by the different clay body types see the section entitled 'range of bodies'. Please also note that the firing temperature has a significant affect on the fired colour!

The making Process

The making process you intend to use to shape the body is also an important factor when considering the most appropriate clay body. Clay body sub-types allow you to select a clay suitable for all major forming operations including throwing, hand-building, sculpting, casting or machine making.

Size of your work and end use

The size of the pottery piece you plan to make is also important. Larger pieces often require a more heavily grogged (less plastic) clay whereas smaller pieces of work can require more plasticity. In addition, the end use of the ware, whether it is purely ornamental, for outside use, or designed as functional tableware will affect your choice of clay body.

Texture

For the more experienced potter the texture of the clay body after firing is often important.. The feel, look and strength of the ceramic piece is strongly affected by this sub-type of clay. For example the grogged subgroup of bodies generally add texture, strength and stability, whilst an ungrogged body will result in a smoother more polished finish.

Glaze compatibility

Whichever clay body you choose it is imperative that you select a glaze which is compatible with the body. This technical compatibility is critical to producing an intact piece without faults after firing. Be guided by your supplier who can supply compatible glazes for most body types and firing schedules. For peace of mind you should always test a sample of the glaze and clay body in your own kiln prior to any major production. The temperature and firing schedule of your kiln will influence whether your clay body and glaze are compatible after firing.

Range of Clay Bodies

The are numerous clay bodies produced commercially around the world available to the craft potter, studio potter and commercial pottery. Indeed there are so many that it is impossible to detail them all here. Bodies are often developed to make them suitable for the making process. Therefore suppliers often state  subtypes which define which clay bodies are more suitable for hand throwing, casting, hand building etc.

Clay bodies however can be classified into a relatively small number of categories according to their colour, firing range and texture. Below are a few major examples showing the fired colour of individual body types.

Porcelain

Bone China

Earthenware

Stoneware

Terracotta

Bone China

Bone China

This is a smooth textured extremely white firing body that is also translucent. It is unique in that it contains a high proportion of calcined bone ash . Biscuit firing at approx 1220 C gives it a high strength making it suitable for producing delicate highly decorative items as well as tableware. This type of ware after glazing is often decorated with onglaze colours or precious metal decoration to create stunning pieces of pottery. Electric firing kilns usually produce the best bone china quality.

Porcelain

This is a smooth textured translucent extra white firing body similar to bone china. However two types of porcelain are made, a 'hard porcelain' which requires a glaze firing in excess of 1400 C and a 'soft porcelain' which requires a glaze firing to approx 1250 C. Biscuit firing however is often around 1000 C which allows pieces to be glazed more successfully. High temperature gas kilns are often used to fire this type of body. Porcelain, like bone china, can also be decorated with onglaze enamels and precious metal to create delicate highly attractive giftware as well as tableware.

Stoneware

Stoneware

This class of clay body is commonly used by craft and studio potters. It has a relatively high biscuit firing temperature in excess of 1150C.  Many commercial bodies, available in a range of off white to buff colours, are fired in the range 1250-1300C to give maximum strength. By glazing with a reactive type coloured glaze a wide variety of effects and colours can be achieved. Because of this stoneware has found high popularity with craft potters looking to create unique coloured or or textured hand made pottery. This body type can be used to produce both decorative and functional pieces such as tableware.

Terracotta

Terracotta

This class of body is typified by its unique red terracotta colour. This clay body has a high iron content in its mineral components giving the unique red colour. Like stoneware the smooth texture can be modified, by addition of grog (coarse material), to give a much rougher finish. Terracotta bodies have a relatively low firing temperature of 1000-1050C and are therefore porous and have relatively low strength after firing. Commonly unglazed it is often used for sculptures, planters, tiles and garden ware where the technical properties are not so demanding. For more demanding environments such as tableware the body is often glazed to give a stronger more durable product.

Earthenware

This type of body is often used for hand painting by hobbyists.

For craft pottery this body is biscuit fired to approx 1000 C to allow easy brushing of underglaze colours or coloured glaze on to the porous surface. Following  glaze firing to 1050 C to 1150 C the body colour and underglaze colours show through the transparent glaze producing highly decorative ware.  After glaze firing the body remains porous with reduced strength compared to fully vitrified bodies like porcelain or bone china.

Body colour ranges from white to buff and some bodies are also grogged to provide texture.

For commercial tableware optimum body strength is achieved by firing the biscuit in the range 1180-1220 C but this peak is not often needed for lower strength or decorative only ware.

Special bodies

This range of bodies include, highly coloured bodies, low firing bodies, Raku bodies, and special highly textured bodies. In the case of Raku the body is modified to allow rapid heating and cooling without  cracking, usually by the addition of grog. Making raku pottery successfully requires more expertise than other pottery types and often depends on a trial and error approach. To learn more about Raku read my separate article on Raku making.

Summary

Clearly, choosing the right clay body for you poses a number of technical questions. It is more difficult than is immediately obvious. However I recommend you talk to your clay body suppliers in the first instance and not just search the internet. Their vast knowledge of their products will make the whole process of selection of suitable body and glaze just that much easier.

Good Luck
Happy potting!
The Potters Friend

More information and other technical articles on pottery and ceramics can be found at my website The Potters Friend.

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How to choose your pottery kiln

K&F front loader

Making a kiln purchase is a big step for many potters. It is probably the biggest financial outlay you have as a potter and you would expect a new kiln to last 10 years or more depending on frequency of use. Most pottery beginners start by attending pottery classes and having their ware fired by the tutor. After developing your skills and with a long term commitment to pottery making you are in a better position to decide your needs:-

Set your Budget

Decide your budget. Make it realistic and include cost of delivery and installation. Also don't forget internal shelves and supports are not usually supplied as part of the kiln and need to be purchased separately. Include a good temperature controller. A kiln is only as good as the controller! Remember planning permission maybe required for some external installations? Decide whether you want to buy new or second hand. Although this will vary considerably as a rule of thumb a good quality second hand kiln  is often about 20% cost of new.

Select the energy source

Decide what type of kiln energy source you will use. Often the type of ware and pottery you intend to make can determine this. For example reduction firing of glaze will require gas or oil firing whilst decal firing is better done in electric firing. It is worth noting that, in general, electric is a cleaner and more controllable fuel than gas but more expensive. Other fuel sources such as Oil, LPG, and wood vary tremendously depending on location and availability.

Identify kiln size and site and type

Decide what size and where it is to be located, does it need special ventilation? How many pieces do I want to fire now? and the future? What size or weight will they be? Will I fire bisque and glost and decoration?

Whether to choose a front loading or top loading kiln often depends on the size and number of the pieces you wish to fire. Generally top loading kilns are smaller than front loading kilns which are easier on the back for placing and unloading.

Visit showrooms or research online

There is no substitute for seeing the kiln you want to buy in person. This will give you a real sense of size and ease of use. A good supplier of kilns will have a range of kilns for display purposes and talk you through many of the decisions you need to make. However as a general rule you need to know the following before you talk with your supplier

What size and shape of pieces you wish to make and how many?

What temperature you wish to fire glost or bisque or decal

Whether you have refractory shelving and supports for the pieces you want to make.

Whether you have 2 or 3 phase electric supply. Domestic supplies are predominantly 2 phase.

Whether you have mains gas supply or other

Calculate firing costs

It is possible to work out the firing costs using the KWH rating or gas usage as a guide. For smaller hobby kilns the difference in costs between gas and electric may not be high but for bigger kilns this needs to be factored in to your buying decision. Again a good kiln supplier will be able to advise you on this.

Choose both for now and the future

Make your selection based on your plans for the foreseeable future. Agree the price for everything including the set up of kiln in its final location not just to your doorstep. Unless it is a simple domestic plug in kiln, employ a professional electrician or gas fitter to ensure your kiln is installed correctly. This gives you peace of mind as well as meeting any legal requirements.

Test out the kiln 

Once you have your new kiln installed test it out first with known tried and tested body and glaze. New kilns can take a while (a few firings) to settle as the refractories are more porous than a used kiln and the gasses from firing soak into the brickwork.

Happy Potting!

Enjoy the new sense of freedom having your own kiln brings and good luck!

More information and other technical articles on kilns, pottery and ceramics can be found at my website The Potters Friend.

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Starting out in Pottery? Read this first!

Making pottery is just like baking  a cake but more complex!

I can tell you one thing about pottery that is in-disputable. It is diverse and more complex than you could ever imagine. Think of it as being like baking a cake. There are literally thousands of different recipes and baking instructions, including the one your grannie used to make! Many of the cake recipes make great cakes but they are all slightly different.

 Clay bodies and glazes are just the same but even more complicated! This is what many potters find fascinating. They can develop their own clay body, glaze and process in a way that makes them special and their pottery products unique. Please remember that!

 However for the novice all this complexity creates confusion. Listening to more experienced potters providing a snippet of knowledge is not always good for you. Beginners try to relate it to their needs and often it results in failure.

 So here is what the beginner really needs to know and not forget.

Start with a pottery class

Start with a pottery class. Here you can learn the basics with the support of a tutor. You can meet new friends and even take comfort in that you are not alone in your struggles to learn a new skill! A good tutor will not only guide you but provide material recommendations to allow you to reach the next stage of working alone.

Choose a Quality Clay and Glaze supplier

Clay Body

If you must go it alone there are many suppliers out there who can help you make the right choice of initial materials. They have the experience and knowledge of a wide range of clay bodies and glazes.
Tell them what you want to make and how. For example. "I want to make pottery by using a potters wheel. I want to glaze it with a white glaze by dipping and I have a pottery kiln that has a maximum temperature of 1250C. "

They can then provide a clay and glaze that are compatible which when processed correctly will give you the best possibility of success.

Process the clay and glaze as recommended by the supplier 

Orton Cones

The making and firing process used to make the pottery is as important as the clay and glaze materials. Therefore process the clay and apply the glaze as recommended by the supplier. Fire the clay and glaze in the kiln as recommended by the supplier.  Firing is often controlled by a firing cycle input into an electronic controller and/or Orton cone values. For more information on firing read my detailed article how to properly fire your pottery.

Once you are happy with the finished result repeat it several times. This proves the process you have  used will work consistently as well as giving you confidence in your skills.

Make a note of the clay body, the glaze, the firing schedules and take a photo of the fired appearance. In this way you will always have a record of how to reproduce your great work of art!

Only once skilled add your own artistic flair

Making pottery is a combination of art and science. The art to design something unique and the science to make it into a product. Only when you have the basic pottery skills and can repeatedly create the same basic product should you become focused on artistic flair.

Developing  your own style and delight in making something unique

Lori Duncan Raku

Potters are often most satisfied when they have developed their unique style or products. Using baking as analogy, top bakers often specialise in making bread, cakes or pastries and have their one stand out dish. Likewise potters specialise in stoneware, raku or wood firing or other depending on their influences.

However they develop this over many years of making and studying pottery. 

So do not rush to specialise too early. What all master potters have in common is a strong basic knowledge of clay, glaze and firing.

Keep on learning and enjoy

Pottery making is meant to be enjoyable so make sure this happens. One way to do this is to continue to learn new things. In pottery making this is relatively easy as the subject is so diverse and changing that you never become a master of all.

Once adept at basic skills look at all elements of what you do not just the making technique. Using materials such as colour creatively can open a whole new spectrum of ware. For example if you only made plain glossy white, look at making some coloured glazed pieces.

One way to do this successfully is to enrol on a pottery course specialising on one type of technique. For example studio potters often run courses to help others develop their knowledge of raku or wood firing or sculpting etc. For more information see my list of pottery courses/classes available in the UK

Above all enjoy!

Good Luck
Happy Potting
The Potters Friend

Burnishing unfired clay pottery

Burnished ware by David Greenbaum

I recently came across the term 'beeswax pottery' and wondered what it meant. I discovered that it was a form of burnishing clay pottery to give it a smooth attractive mainly waterproof finish. Previously, to me, burnishing was just a term for the polishing of gold decoration used for the decoration of pottery.

It reminded me that you never stop learning with pottery. It is such a wide subject which continues to grow as new techniques are invented (or old ones re-invented!).

 History of clay burnishing 
Many ancient potters used burnishing to make their pottery harder and more waterproof before they discovered the use of glazes. Nowadays, modern potters choose to finish their work by burnishing because of the subtle, but beautiful finish achieved using this method. A burnished pot often has a soft, tactile quality all its own. However modern potters also need to know that this type of pottery should be used for decorative purposes only and not for ware intended for contact with food or drink.

Health and safety considerations are now a more important part of our modern life!

 So What is Burnishing and how is it done?

Burnishing is basically rubbing the surface of the clay piece until it becomes glossy. To achieve a satisfactory finish it often takes several hours for even a small pot. Skill and practice are required for this technique as it is highly influenced by the state of drying. The best stage to burnish is usually at the later stage of leatherhard. However many potters burnish the piece more than once to achieve the ultimate finish.

Working in very small areas, applying a little lubricant at a time to the piece, rubbing in different directions will gradually create a sheen. Care is needed as sufficient force is needed to compress the surface but not create a hole or flake. After firing the sheen is mostly retained and can be improved by polishing with beeswax or other types of wax.

 Some key factors to consider when using this technique include:-

  Choose your clay wisely
Burnishing requires either a very fine clay body, or fine clay engobe. Clay bodies which contains grog or sand are therefore not recommended for this technique. Low firing clay bodies such as earthenware are also recommended as higher firing bodies can give rough texture after firing.

Choose your shapes wisely
Pots with smooth flowing surfaces are easier to burnish and look so much better when fired. Complex shapes with sharp corners or surface features will be almost impossible to burnish properly.
  
Choose your tools wisely

The burnishing tools you use need to be smooth, hard and easy to hold. As burnishing is a very time consuming process comfort is an important factor and this is a personal thing. However most potters use the backs of spoons or polished stones for this technique. Some potters carry out a secondary burnish using smooth plastic or other materials.

Choose your burnishing oil wisely.
To aid the burnishing process the use of a burnishing lubricant is recommended. The lubricant allows the clay to densify and give an even smoother finish after firing. . Lubricants that are often used include vegetable oils, lard, and water. Although the choice of lubricant is subjective, water is the least recommended as there is a tendency for it to soak into the body or flake the surface as it is pressed.

Firing 
Firing of the ware after burnishing is important and can alter the texture of the surface significantly. Low firing clay bodies appear to work best.

 Post firing polishing 
 Firing gives the burnished ware a lovely, tactile soft feel. In ancient times, animal fat, oil, and wax were often used to make it more waterproof and to restore the pre-firing high gloss. Today, most potters use a  form of wax. Paraffin wax, candle wax, and beeswax, have all been used successfully. By applying the wax to a small area of heated ware and polishing a high sheen can be achieved.  The result is an outstanding piece of decorative ware that often looks as though it has been glazed but feels so different!

If you found this article of interest make sure you read about Terra Sigallata a method for making shiny ware without the polishing stages!

Of course more information and other technical articles on pottery and ceramics can be found at my website  The Potters Friend. Go now to sign up for my free  newsletter.

How to Choose a Pottery Class

The Benefit of Classes

Learning how to make pottery whilst enjoyable in its own right, can be enhanced by professional teaching and sharing of experience with other students.

Classes help people learn quicker and provide the right learning environment to enjoy the experience as well as make friends. This should not be underestimated as many frustrations will become apparent along the way..There are both studio potters who run classes in evenings and weekends as well as local colleges who run part time and full time courses.

Be clear on your needs

One question you need to ask yourself is "do I want to learn the practical skills such as throwing on a wheel or do I want to have a good scientific/artistic understanding?" Knowing this will help define your teaching requirement.

I recently read a debate about when should you call yourself a potter? It was interesting to note that most people shared my view that "you never stop learning in pottery". As pottery making is such a wide subject, you can be an expert in part of it and a mere novice in another area.

Therefore at which point you become expert or call yourself a potter is purely arbitrary.

This point is important as you need to find an expert teacher in the area of pottery in which you want to learn more. 

Choose the right teacher and class

Choosing the right pottery class is not always easy. For example, if you have an interest in learning the basics of  pottery making then joining a class learning about Raku firing is less useful. Similarly if you purely want to learn artistic skills such as hand painting of china as a hobby, there is no need to learn about slip casting of bone china. Clearly it is important to ask the right questions to make sure a class meets your specific needs.

Some helpful links

The following links and brief details of classes may be helpful. Unfortunately I cannot make recommendations as there are so many of which I am not personally familiar. Therefore when making an enquiry please ask for references from previous satisfied clients and ensure that the classes meet your needs etc

Good Luck and enjoy!

Pottery Classes in USA
Directory of Pottery Classes, Courses, Lessons, Events, Workshops, Free Classes, in USA
Pottery classes and Art courses in UK
Directory of Pottery,arts and crafts classes, workshops and painting holidays in Britain and Europe.

More details of individual classes and workshops can be found below:-

Details of UK pottery classes

More information and other technical articles on pottery and ceramics can be found at my website The Potters Friend. Go now to sign up for my free newsletter.

How to properly fire your pottery

The firing of pottery goes back over 3000 years. In those days wood fires were the source of energy. However today so many other forms of energy are available including wood, coal, gas, electric, oil, microwave, wind, solar to name just a few.

For the small pottery craft studio or hobbyist however the most common means of firing pottery are by the use of gas or electric kilns. Generally electric firing is a clean means of firing whilst gas is thought to be more energy efficient. Let us consider the basics of each:

How does electric firing work?

The principle of electric firing is relatively simple. Imagine a box or cylinder kiln fitted with heating elements like your domestic oven. However, instead of heating to 300C it is capable of heating to 1300C.

Operation of the kiln starts when electricity is applied to the elements ( resistive load ) causing them to heat rapidly. The heat is transmitted to the pottery mainly by radiation. Special insulating bricks, called refractories, line the floor,walls and roof of the chamber to prevent the heat generated from escaping. An electronic box, called a temperature controller,linked to a thermocouple (special wire) inside the kiln, measures the temperature constantly in the chamber of the kiln and then controls how much electricity is supplied to the elements. This in turn controls the rate of increase or decrease in temperature within the kiln.

How does gas firing work?

The principle of gas firing is also relatively simple.. Imagine this time that the box is kiln fitted with a burner or burners, a little like your domestic gas oven. However, instead of heating to 300C it is capable of heating to 1300C and because of the large amount of gas used the kiln needs a chimney or flue.

Operation of the kiln starts when the gas is turned on and burner lit. The heat is transmitted to the pottery mainly by convection and radiation causing it to heat also. Special insulating bricks, called refractories, line the floor,walls and roof of the chamber to prevent the heat generated from escaping. A vent in the roof or rear of the kiln leading to a chimney allows combustion gases to be removed from the kiln. An electronic box, called a temperature controller,linked to a thermocouple (special wire) inside the kiln, measures the temperature constantly in the chamber of the kiln and then controls how much gas is supplied to the burner. This in turn controls the rate of increase or decrease in temperature within the kiln.

How do I fire the kiln properly?

For both electric and gas firing the two critical factors which affect the success of your firing are peak temperature and uniformity of temperature within the kiln. Peak temperature can easily be measured using the thermocouple fixed inside the kiln. Uniformity could also be measured using a series of such thermocouples located in different sections of the kiln. However this would be an expensive option for smaller kilns.The use of Bullers Rings or pyrometric cones to confirm the consistency and uniformity of firing at different locations within the kiln is more cost effective.These ceramic cones or rings can be placed next to your ware and will experience exactly the same amount of heat as your item. By measuring the values of the rings or cones after each firing you can be assured the firing is consistent from one firing to the next.

But what is the peak temperature?

The peak temperature on firing biscuit or glaze is the maximum temperature reached on firing. This value depends on the type and composition of the clay body and glaze used. As there are literally thousands of body and glaze compositions,suppliers of body and glaze products therefore recommend a peak temperature or ring or cone value equivalent suitable for optimum firing their products. It is advisable to follow their recommendation.

But what if the temperature isn't consistent?

Quite often there is a spread of temperature within the kiln. It is quite common to have a 20 C spread in temperature between the bottom and top of even small kilns. The reason for this is dependent on a number of factors. Rate of firing, kiln design and condition (age and condition of brickwork),element condition and age (for electric kilns) gas/air ratios and flame (for gas kilns) and ventilation aspects of the kiln are all key factors.

For uniform firing of kilns a slower temperature rise to peak temperature and a soak at peak temperature will reduce variation of temperature within the kiln. Indications of non uniform firing of glazed pottery are variation of gloss, colour and or bubble between similar fired pieces.

Summary

Peak temperature and uniformity of temperature are the key factors determining the success of your pottery firing. Peak temperature is measured using a thermocouple connected to the digital display of a temperature controller. Uniformity is measured using Bullers rings or Cones placed in the kiln next to the ware. The heating rate has an affect on both and should be relatively slow for best results. A cycle of more than 12 hours cold to cold is quite common. However you should be guided by the body or glaze supplier as they know the optimum cycles for their products.

More information on firing of pottery and ceramics,including Bullers rings and Orton cones, can be found at my website http://www.pottersfriend.co.uk Go now to sign up for my free newsletter.

Raku Pottery

What is Raku Pottery?

Raku is a pottery technique that originated in Japan in the 16th century. The technique involves a specific rapid firing process at a relatively low temperature but the whole process can be much more complex.
The technique has developed and there is now the traditional Raku and a western version of Raku. The results of this type of process are very unique from other firing techniques, and some fantastic metallic finishes, crazing and other decorative effects can be achieved.

The process in brief

In raku, the pottery pieces are loaded into a cold kiln (for multiple batches pieces are often preheated and loaded into a hot kiln). The kiln is heated rapidly with the ware reaching temperature in as short a cycle as 15-20 minutes.This contrasts with traditional firing cycles of 10 hours or more!

Glaze maturity is judged by the trained eye without the use of cones or measuring devices. Often this is when the glaze has begun to melt.
When the firing is considered to be complete the ware is immediately removed from the kiln while still red hot using tongs or another lifting device.This is the stage in the process where traditional and western raku differ in technique and treatment.

In the western version the ware is treated to a post firing reduction. To achieve this the hot ware is put into a container, usually a garbage can, with combustible material such as paper, sawdust, or leaves and allowed to smoke for a predetermined length of time (usually about 20 mins). The carbonaceous atmosphere (black sooty smoke) reacts and affects the glazes and clay and imparts unique effects and surfaces to the wares. Some of these effects are metallic and crackled glazes surfaces and black unglazed clay.

When the ware has cooled, it is washed with an abrasive cleaner to remove all residues of soot and ash. In this way it is possible to produce a unique piece of art pottery. Unfortunately because of this rapid process the ware is relatively fragile and the decoration not food safe. Pottery made in this way must only be used for decorative purposes.

The Process in detail

The Clay body

Raku bodies are designed so that they allow rapid heating and cooling without cracking. Most raku bodies (but not all) use a recipe that is high in grog (coarse material). A range of Raku bodies are available from suppliers to match your making and firing process.

A typical body recipe might include by parts weight:-

Clay 65-75%
Grog 25-35%
Talc 0-15%

The type and amounts of each component will depend on many factors. These include the clay making process, the fired body colour and texture required and the firing temperatures to be used.
One of the important questions you need to answer "will the glaze and body combination I intend to use give me the glaze finish I require?". For example many glazes used on Raku will readily craze if the correct glaze/body combination is not used. For some this might be an appealing effect. For other Raku makers it may not. So choose your clay body wisely.
The clay body for raku is typically bisque fired to cone 04 (1060C) prior to glazing. This gives it sufficient strength for handling during the glaze firing process, as well as some porosity to aid glaze application.
Most clay suppliers will help you choose an appropriate clay body. Biscuit firing of the clay piece is essential if the pottery is to avoid breakage on firing.

The Glaze

Next you can apply slip, apply glaze, or just leave the pot bare. Any glaze that will melt successfully during the raku fire could be used. The most important factor in identifying potential raku glazes is the temperature at which they mature, how you plan on using them, and what kind of effects you are looking for. Low fire glazes generally give the best results. Most raku is fired in the range of cone 010-06. (900-1000C) Note the surfaces of the pot that are not covered with glaze will however turn black from carbon from the post-firing reduction process.
For more info on Raku glazes see my separate article on Raku glazes.

Raku (glaze) firing

Northern Kilns Raku kiln

The pottery is placed in the kiln and rapidly heated to the point at which the glaze melts. Although a pyrometer is sometimes used to monitor how fast the temperature is rising, Raku artists usually watch the glaze to see when it is ready to be removed from the kiln. Depending on the glazes and technique used, this might be when it gets shiny, or when it bubbles and/or looks like orange peel. Transfer of the ware from kiln to the reduction chamber is important. Speedier transfers can give metallic lustres whilst slower transfer can give brighter colours.

Types of Raku kiln

For firing of multiple loads the temperature of the kiln must also be readily controllable. An electric kiln is perfectly suitable for raku although there are some special considerations that require careful attention. Cut off switches must be used to avoid any contact with live electrical current when the electric kiln is opened. Many types of gas and electric kilns can be used for raku. Kilns need to be located outdoors or in close proximity to the outdoors or have lots of ventilation. Access to the pots inside the kiln is critical so they can be easily removed. Raku kilns are therefore designed to provide this easy access to red hot pots.
More information on Raku firing can be found the Potters Friend website

The Reduction Process

The reduction chamber (garbage can) is prepared by adding the combustibles. There are many things that can be used, but newspaper, sawdust, or wood chips work well and is abundant. After switching off, the kiln is opened and hot piece removed from the kiln with tongs or a lifting device. Immediately it is placed in the reduction chamber (garbage can) where the heat sets the combustibles alight. The lid of the can is replaced and the chamber left for about 20 minutes.

After the pot has completely cooled, it is possible to use Ajax cleaner or similar to clean carbon off the glaze and "shine up" the piece. Reduction is a firing term that refers to a lack of oxygen in the combustion process. By sealing the can with the lid the can is deprived of oxygen. This lack of oxygen causes incomplete combustion of the paper or sawdust to take place and creates the metallic finish on the glaze.

Safety

The raku process is a dangerous process as you will be exposed to high heat, flames and smoke. Always wear fire protective clothing, fireproof gloves and protective eyewear. Do not open or insert tongs into an electric kiln without shutting off. The reduction process (container with combustibles) should take place outside of building due to flames and smoke. Do not apply spray glazes without a NIOSH approved respirator and other personal protective equipment. Although many glazes are Non Toxic and Non Hazardous when used according to manufacturer’s directions, this is not always the case. It is important to check! Raku glazed items are suitable only as decorative ware and are not recommended for contact with foodstuffs.

Ten pottery making tips for the beginner

My top 10 pottery making tips for the beginner

1. Go to pottery making classes. Everyone has to learn somehow. Although it can be comforting to learn on your own it will be much more fun with others. In addition your skills will improve much quicker!

2. Don't be put off by the terminology! Pottery making uses some strange and quirky terms. But dont be put off! It wont be long before you know green ware from biscuit ware.

3. Be prepared to get dirty-you can tell a potter by his hands and shoes!Even with an apron it is impossible to stay clean when making pottery. Your hands and shoes will get dirty! Treat it as part of the fun so dress appropriately.

4. Enjoy the experience-dont be put off if it goes wrong!It goes wrong for everyone including the experts so don't be afraid to experiment. Remember that your designs are unique and you have the chance to express your own creativity.

5. Read some simple pottery making books. Lots of pottery books are available so choose books with simple descriptions and pictures to get you started. My recommendations can be found at www.pottersfriend.co.uk/books/list_books.php Books,however, are no substitute for classes but they should reinforce your learning.

6. Ask questions. Asking questions aids memory so you learn quicker. Don't be embarassed to ask even the most simple of questions. Remember you are probably only saying what many others are thinking!

7. Practise then practise some more!This probably should be my number 1 tip on the list. As with most things in life, the more you practise the more skilled you become and the more enjoyable will be the experience.

8. Develop your own style. Dont be afraid to experiment-its your chance to show your artistic flair.

9. Make some pots & give them away. It makes you feel good and you might even find a soul mate.

10. Share your experience with a loved one. Making pottery can become a real passion so dont forget to share your experiences with your loved one. They might even want to join you at the next pottery class.

For the more experienced potter why not visit my tips page at www.pottersfriend.co.uk/tips.php

Alternatively why not test your pottery knowledge with my quick pottery quiz www.squidoo.com/potteryquiz

Making pottery-simply art or sophisticated science?

As I was watching an experienced potter throw beautiful shapes recently it made me reflect 'how incredibly simple it seems in the hands of a true expert'! Starting from a lump of clay, shaping it into an interesting form, drying, finishing, glazing, and firing can take up to 2 weeks. A labour of love to create that special unique piece! But those who have tried to make pottery know that these are mere headings for skill, artistic flair,experience and a good deal of knowledge and science.

Incredibly, in the pottery industry where 'lean manufacturing' is all the rage they attempt to produce finished ware in a matter of hours! They breakdown every operation down to its most basic level (steps). Each step in the process is identified and the skill, tools, material, manpower and time required. By defining the process in this way it is possible to identify the number of steps and value of each step in an operation. Lean manufacturing philosophy requires the removal of waste in all its forms. Waste doesn't mean just waste material, but wasted human movement, wasted product movement, overprocessing, excess stock, not right first time, or wasted waiting time.

Often the target is to improve efficiency and the first step is to remove as many non value added steps as possible. An example of this might be to remove the clay ware from the sponge/fettling stage immediately to the biscuit kiln instead of to an intermediate storage area. Often by looking at operations in this way new or more robust ways of processing are identified and introduced.

"So what" I hear the true potter say-this means nothing to me. And he is right in some ways! It is often by trial and error that his artistic flair can flourish. A missed out glaze ingredient creates that wonderful new glaze colour or the kiln underfires showing unusual but unique glaze effects!

However he is also wrong in some ways. He has already adopted some of the lean principles without knowing it! Often the potters studio is laid out so all his tools, materials equipment are close at hand (thereby reducing waste movement). He recycles the clay and glaze (reduces waste materials) and tries to make a number of items at a time not just one (reduces waste time).

I believe that both the studio potter and industrial potter can learn from each other. The studio potter can learn to reduce waste allowing him the time to be more creative and the industrial potter can learn to be more creative in design allowing him to sell more product.

Surely making pottery is both a simple art and a sophisticated science! What do you think? I'd welcome your comments.

Pottery Clinic

Glaze blister at high magnification

Post your questions about any pottery or ceramic matter.

All questions are welcome regardless of how simplistic they may appear !

My commitment is to respond in a timely fashion and to provide the best advice that I am able to based on my own perspective and the information provided.

I look forward to answering your questions