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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Why do I need frit in my glaze?

A glaze after firing can be considered to be a glass. Therefore it is not surprising that traditional glass making materials such as quartz, limestone, and felspar are commonly used to make glazes. However glazes which are intended for firing below 1150C need other elements such as lead or boron and alkalis to create the right properties. To enable these elements to be included safely they are often pre-melted with other glass making materials to form a FRIT.

What is a frit?

Borosilicate frit

Lead frit

China clay

A frit is a a pre-melted glass which is granular in nature. Once crushed and ground to a fine powder it provides the basis for all low firing glazes. Often a glaze contains merely one frit and clay. The clay is added as a suspending and binding agent to aid glaze storage, application and firing.

How many frits are there?

There are literally thousands of frits. The compositions have been researched and developed over a long time period to provide the right technical properties such as fusibility, thermal expansion and durability. A wide range of properties are needed to meet the wide range of bodies and firing cycles used by manufacturers and craft potters.In general terms frits are normally classified as transparent or opaque and then lead containing or lead free.For environmental/safety reasons lead containing frits are gradually being phased out and replaced with lead free alkali borosilicates.

Can I make my own frits?

It is possible but not recommended. Large scale frit manufacturers often make frit by a continuous method in a high temperature box type kiln using specialist refractory linings. These kilns produce tonnes of frit per day, meaning they can achieve consistent high quality output. For other than the most demanding glaze requirement, making your own frits is unlikely to be cost effective.

How many types of frit do I need?

This depends on the number of clay bodies and firing cycles you employ. As a basic requirement you need a transparent frit, an opaque frit and an expansion modifier frit. These should allow you to make transparent, opaque and semi opaque glazes suitable for conversion to coloured glazes by adding colouring pigments.

Why not use frits in all glazes?

In theory this is possible but the costs would be excessive. For example high temperature stoneware and porcelain glazes can be manufactured with lower cost glass making materials such as felspars, quartz, limestone and clays.

Where can I buy frits

Most pottery material distributors sell small quantities of powdered frit suitable for the studio or craft potter. Industrial scale potters may buy the frit direct from manufacturers such as Endeka, Ferro or Esmalglas.

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.

Pottery Glaze Safety

Introduction

The safety of pottery manufactured by credible large scale pottery manufacturers particularly in Europe and the USA is a priority. However many smaller scale studio potteries have a lesser understanding of the leaching of toxic components from glazes. Why? Because it is difficult to understand and even more difficult to test accurately without specialist equipment.

However everyone involved with pottery manufacture needs to understand about glaze toxicity in the 'sue everyone' culture of today.

Changes to legislation in the USA in the early 90's provided the springboard for worldwide change.

A case of lead poisoning in the USA caused by pottery which did not conform to any legislation worldwide (YES NON CONFORMING WORLDWIDE!) led to big changes. The result of the political intervention that followed was to effectively ban lead glazed ware (under proposition 65) in California and many other US states.Whether this was a justified scientific solution to the original problem is still debated by many in the industry. However the result is here to stay.

Lead in Glaze

Lets start with some facts about lead :

• Lead in large quantities is known to be toxic. Indeed the ancient Egyptians used it for homicidal purposes.
   
• Lead in small quantities is known to be harmful. It can seriously affect the learning ability of small children and cause other harmful effects in adults.
   
• Lead glazed pottery leaches lead when subject to strong acids. However this may be as low as parts per billion; less than might be found in drinking water!
   
• Lead leaching from the glaze surface is not directly related to the lead content of glaze. Many other factors such as firing have an equal or greater influence.
   
• Lead glazed pottery has been in existence for thousands of years

Clearly the picture for lead glazes is not good. However the technical understanding gained over many years of industrial research and manufacture allowed them to be used with relative safety. Nonetheless the pottery industry has moved forward.

 Environmental as well as political pressures has ensured that millions of pounds have been spent to research and develop unleaded glazes and colours by major manufacturers. Unleaded glazes and colours have now become the norm and are available for most types of pottery body.

But unleaded glazes are not without issues. Lets consider why:

Unleaded Glaze

Unleaded glazes are mainly glass, sometimes with a crystalline phase and are considered as long-lasting and indestructible. This is not strictly true as all glass leaches to some extent when it comes into contact with acid foodstuffs even water. In the case of acids,  contact with the glaze surface over a period of time can cause a much greater leaching effect. The intermittent use of alkali dish-washing agents can also dull the glaze surface leaving it more prone to acid attack. Early unleaded glazes were particularly prone to this type of attack by strong dishwashing detergents.

Some unleaded glazes contain elements such as Barium, Zinc and Cadmium which are also considered toxic when released in large quantities from the surface of the glaze. Indeed some countries legislate for this by imposing limits on the release of cadmium and zinc elements and other heavy metals in their metal release legislation or guidelines. The safe handling of barium carbonate and cadmium compounds in the manufacture of glazes is also a concern for glaze producers.

Coloured Glazes

Copper green glaze

Coloured glazes have long been known to give greater problems than white glazes in terms of toxic metal release. This is due to the often overlooked fact that the choice of pigment greatly influences the ease at which acids can attack the glaze surface. For example it is well established that the combination of copper and lead in a glaze gives significantly greater lead leaching than from the lead glaze alone.

Other colouring elements such as cobalt, manganese can act in similar ways even in unleaded glaze. Therefore it is important to know the effect of pigments and intrinsic durability of each glaze you make.

Toxic Metal Testing

Toxic metal testing of pottery intended for food contact is carried out by specialist testing organisations who are accredited to carry out standard tests such as EU 2005/31/EC or ASTMC738 in the USA. The most recent European limits for this test is specified in 2005/31/EC. To reduce cost and avoid testing of clearly unacceptable glazes quick tests can be used to screen out poorly durable or lead glazes. Cutting a lemon in half and placing it overnight on the glaze surface is one such quick test. Another is using a quick lead test such as lead inspector.

However it is recommended that all glazes produced for food contact use are tested by certified test laboratories to ensure compliance.

Summary

To produce safe ceramics that comply with current legislation it is important to understand the formulation and firing of glazes. It is  more complex than most people think and testing by a recognised testing laboratory is the only true way to ensure compliance. The problems of safety of  lead glazes are well known, and these glazes are being phased out and replaced with unleaded equivalents. However unleaded and coloured glazes are not totally free of issues and reference to the health and safety glaze documents of suppliers is strongly recommended.

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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Pottery Materials-Potters You've Never Had it So Good!

Sources of materials

Materials dug from the ground have been the source of pottery making for thousands of years. However early potters relied heavily on local materials, especially the clays and sands. This was certainly the case in my beloved Staffordshire, England where local marl clays formed the major source of clay for early industrial potters.

Borax granules

Today materials are shipped around the world to areas of high industrial scale ceramic manufacture. For example the high quality white china clays from the south of England are often shipped to Asia to make the finest bone china and porcelain bodies. Similarly borax and boron minerals from Turkey and the USA are used in Europe to make glazes and frits for tile, tableware and sanitary ware manufacture.

However it is not just the source of available materials but also the quality and consistency that has helped modern potters and potteries to improve their quality, designs and efficiency.

Materials for body making

Body materials

The main materials used to produce a clay body are silica or quartz, felspar, and clays. These materials come in various purities, particle sizes, and qualities. To produce the finest white bodies, high purity low iron materials are used and these materials are sourced locally where available. However most areas of pottery manufacture do not have the required purity or consistency required from all their local suppliers and are therefore forced to consider other supplies. It is the consistency in purity, and control of of material properties that has made a significant difference to large scale pottery manufacturers. They can automate processes and improve efficiency to reduce costs. Materials are now stardardised to fit processing routes. For example 30 mesh and 200 mesh materials are common in the UK. These improvements in materials for industrial scale customers also has a knock on benefit for craft, hobby and studio potters who can also purchase these same materials from distributors and use them with greater confidence.

Materials for glaze making

Frit granules

Like body the main materials used for glaze making are silica, china clay, and felspar. However frits (fused glass fragments) and other minerals such as limestone, dolomite, wollastonite, zircon are often added to control the fired properties of the glaze. Expensive technical grade chemicals such as zinc oxide, barium carbonate,and boric acid are also used in small quantities in the glaze or frit to meet the most demanding glaze requirements. However it is in the use of boron products where industrial scale and craft scale differ the most. Large scale glaze manufacturers predominantly use frits as a source of boron, where craft glaze makers use boron products such as Gerstley borate. The benefits of using frits for industrial scale glaze manufacture are far reaching. The recipe of the glaze is designed to be lead free and often fine tuned to give the widest firing range and technical performance. Control of glaze slip properties, glaze application, and firing properties are of paramount importance especially in automated plants which are not suited to the use of borates in glaze. Slip control of the glaze involves controlling both the solids content of the slurry, the viscosity (fluidity) and the drying time by means of chemical additives.

This differentiation in supply is a benefit to craft and hobby potters who can choose a from a wide range of frits or borates depending on their scale of operation or cost needs. .

Materials for decoration

A whole range of  methods are now available for decoration of pottery. When colour was introduced to pottery in early years it was in the form of naturally occurring coloured minerals usually high in iron. Consequently the colour range was restricted to brown- red to grey blue in colour depending on the firing condition. However with the development of pigments from the eighteenth century many more colours became available with Chinese blue colour on white glaze becoming very popular.                                      

range of onglaze decorating colours

Today a full range of stable mixable ceramic colours are available ranging from bright yellow to blue to red. Together with a wider range of decorating techniques the modern potter now has the opportunity to design truly unique ware that is also repeatable.

Range of ceramic stains

To put this into perspective an anology might be to compare Fords "you can have it in any colour as long as its black" to the current range of colours and effects used to paint modern vehicles.

In a similar way to body and glaze materials, decorating colours such as onglaze have become standardised and more consistent in both their application and firing. Colours have been developed without lead and are available in the best medium (liquid) to allow optimum application whether that is hand painting, machine banding or screen printing. Introduction of digital printing has allowed digital images to be translated from computer to ware using ink jet decals or even direct printing in a similar fashion to paper printing. For the hand made purists in pottery computer support to design has not always been welcomed but it has extended the range of design to new levels.

In the future design will be pushed even further by 3D printing which is in its infancy in the pottery industry.

Summary

Clearly material technology and control in the pottery industry has progressed almost unnoticed since the early eighteenth century pottery manufacture. However it has progressed and the development of more consistent, environmentally friendly colours together with a wider colour palette has been of great benefit to modern potters, large and small..  The advent of digital printing in recent years and the potential of 3D printing is set to revolutionise the industry further creating even more design possibilities.

Yes Potters it is true! You've never had it so good!

Comments welcomed?

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 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.

Go now to sign up for my free newsletter.

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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Self cleaning plates and lego style brick houses? Are these ceramics of the future?

Legoland By Copyright © 2003 Kaihsu Tai
via Wikimedia Commons

Self cleaning Glass

I recently read an article about the possible future of textiles. Designers were predicting the living shoe and the strawberry plant that grows lace. Whilst fanciful such ideas have a slim chance of becoming reality.

That made me think about ceramics. What will be the future of our beloved ceramics in 50 years from now? Perhaps it will be self cleaning plates and lego style brick houses? Again these may seem far fetched to most but they are already possible in a small way.

The next 50 years in ceramics - my vision

My vision  is based mostly on what is possible now but not necessarily in ceramics

100% Recycling

Without doubt ceramics will be recycled in a more comprehensive and systematic way. Recycling points will be readily available in every part of the country. Ceramics will be reprocessed by barcode or other tracer systems which will allow them to be separated  for more economic recycling or re-use.

Greater personalisation in Design

The changes in pottery fashion are more rapid now than at any other time. This trend is likely to continue. Changes to our dining habits, less formal dining and more casual dining, is reflected in the ceramics we buy. Ceramics are now mostly considered a disposable item and need to fit more closely with our lifestyles. This has led to a wider choice of colour and shape. For example a whole range of ware may be used for dining instead of a single dinner plate.

The future however is likely to bring us even more personalisation in design. Designs will be agreed at the point of sale or online and products will leave the factory 24 hours later. Scope for designing your own tableware is not far away now and will be common place in the future. Personalisation is already available in a small way but this will grow exponentially as technology progresses.

Lightweight strong ceramics

Abalone Armor Paper-thin armor courtesy of nature Andreas Walther

Ceramics will become lighter and stronger! Lightweight ceramics have already been developed for military purposes but ultimately these ceramics will become part of the pottery scene. The advantages of light weight and strength are significant not only to the carbon footprint but also to manufacturing and transport costs.

Egg shell porcelain courtesy
of Victoria and Albert museum

 A good example of ultra thin ceramics is Eggshell porcelain , a delicate porcelain often decorated with a watermark-like image dating back to the Ming dynasty (1402-1424). Nevertheless because of lack of strength it has not found widespread use for dinnerware. Future ultra thin ceramics will have sufficient strength to make them suitable for a wide range of ceramics.

Imagine drinking from a paper thin highly decorated mug that is  heat retaining but virtually unbreakable?

Warm self cleaning sanitaryware

Composite materials are mixtures of materials eg ceramic and plastic which when combined give superior properties when compared to the individual materials alone. Such type of materials are common place in the military and aerospace industry. However they are less well used in domestic applications. Nevertheless car windshields are often a composite of glass and plastic. Here a layer of plastic is embedded in between two layers of glass to give extra strength and toughness.

In time other composite materials will emerge in household products. I can imagine a bathroom where the ceramic composites used are warm to the touch, with antibacteral surfaces that are virtually self cleaning. Water is recycled at point of use via ceramic composite filtering systems.

3D Digital printing- or how to doodle your own cup and plate!

2d digital printing of colour

3d digital printing of a sugar bowl

Digital 2d colour printing is already well established for printing of coloured images on to paper. It is already making significant inroads for the decoration of tiles and tableware. In the case of ceramics the 4 colours used in ink jet photocopier type machines are replaced by up to 10 ceramic coloured inks. These are then used to decorate ceramics directly or via an intermediate stage such as paper transfers. The result is a high quality image in rapid time using an amazingly flexible system. But digital printing does not stop there! 3D printing of ceramics is in its infancy. Greater design possibilities as well as the personalisation already discussed above will become the norm.

 But what does this all mean? In essence a 3d computer design will create a 3 dimensional object via a robotic system by building a series of 2d layers. A good analogy would be building a wall brick by brick but at particle or even molecualar level.

 Already there is a 3d printing pen that transfers what you draw into a 3d object in plastic. If you had a pen that would allow you to doodle a 3d object of the future what would  you draw?

Eco Style Ceramic bricks and panels

Eco house from

Although the detail of design, decoration and processes used in brick making has changed greatly in recent years, the basic idea of shaping raw clay into rectangular blocks remains much the same. Ceramic bricks have changed little in hundreds of years. In many ways this is cost driven so will need radical changes in house construction for this concept to change. 

However this is happening albeit slowly as more eco houses are being constructed (in part) off site and delivered to site for final assembly. This trend will continue. The idea of coventional bricks will change as this type of housing grows. It is not too stretching an idea to believe that strong lightweight ceramics in the form of legotype bricks or panels could be used in all future house construction. 

Who knows the eco house of the future could be manufactured entirely off site and only services and fixings completed on site! 

What do you think?

So whilst far fetched I believe many of the above have a reasonable chance of becoming reality. What do you think of my ideas? Do you have some (better) ideas of your own? I look forward to hearing all about them.

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 a Pottery Wheel

Buying a pottery wheel can be quite an expensive issue. Whilst second hand wheels exist it is difficult to judge their state of repair and future reliability. Therefore make sure you make an informed choice. So what factors should you consider when buying your pottery wheel? Weight of clay When choosing a pottery wheel the weight of clay you intend to throw decides the power of the motor you will need for a power driven wheel. Typical weights are as follows: ¼ HP for small pottery items 20lbs (10kgs approx) max for beginners ½ HP for medium sized items up to 100lbs (25 kgs approx) max suitable for most commercial potters 1 HP for large items 200lbs (50kgs approx) for experienced potters making very large items. Quality and ease of operation Quality of wheel can be an issue as it comes at a price. However you should also consider at least: Noise-older type wheels can be quite noisy whilst some recent models are whisper quiet Smoothness of pedal operation Smoothness of wheel particularly at low speeds- a jerky transition of speed can cause difficulties -important for delicate shaping Reversability-can it be used by left and right handed people? Electric or kick-wheel operation? Foot pedal or hand lever operation? Whilst kick wheel models may be cheaper they can take some getting use to if you are already used to an electric powered Wheel head size and predrilled holes- The wheel head size dictates the max diameter of clay piece which can be thrown. Holes in the wheelhead allow a bat (special disc) to be used. Pins allow release of the bat, holding the thrown piece, from the wheelhead. The thrown piece can then be removed easily for drying while a new piece is thrown. Mobility Some wheels are very light in weight and designed to be portable whilst others are meant to be static. Consider if you want to move the wheel between different locations. Heavy powerful wheels can be more durable and long lasting. Examples of different wheel types are: A Tabletop Wheel The Shimpo Aspire can handle your most creative challenges. Its lightweight, compact design makes it easy to transport, and a 20 lb centering capacity makes it a practical addition to any studio or classroom. The Aspire features a 1/3 HP, 100W DC motor, a 7" alloy wheel head, and a removable one-piece splash pan. The wheels speed ranges from 0–230 rpm, controlled by a hand lever. Also included are two 9¾" bats. It measures 9" H × 14½" W × 20" L and weighs 25 lb . Amazing, affordable, accommodating … Aspire! Shimpo’s Aspire Pottery Wheel includes a two-year limited manufacturer’s warranty.   A Powerful model suitable for seated use Brent wheel Model B is designed to fill the needs of schools and studio potters. Competitively priced, this wheel is quiet and solid under 150 lb (68 kg) loads of clay. A 1/2 HP motor provides the power and weight necessary for school use. A splash pan and 12" Plasti-Bat are included. Shipping weight is 112 lb (51 kg). Truck shipment is required. 10-year limited warranty. CE-certified. Super quiet model for seated use-The Shimpo's Whisper Potter's Wheel is extremely responsive, with high torque at all speeds. It's powerful, and by far the quietest pottery wheel on the market. The ½ HP, brushless DC motor has a direct drive (no belt) system and a broad speed range for optimum control. A fixed foot pedal with hand lever operates the electronically controlled motor. The motor is reversible for lefthanded and righthanded users. The 12" wheelhead and two-piece splash pan are standard. Centers up to 100 lbs. The wheelhead also turns freely, so it can be used as a banding wheel at 0 rpm.

Warranty and Cost Warranty and cost often go hand in hand. A warranty can be anything between 1 and 10 years and cost will be upward of $350 dollars for a new wheel. It is worth asking if it can be repaired locally within the warranty if anything goes wrong..

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 Teach Children about Pottery

Make it Fun
You make their first contact with pottery a fun enjoyable experience. Once they have the interest then you might want to add a little practical knowledge. Of course you want your children to be safe so only use safe materials and provide basic hygiene equipment, and instructions such as -wash your hands, and don't put anything in your mouth.

Where should you start?
Most children are familiar with playdo or plasticine. They have probably moulded these into shapes before. So let them use their imagination to form something that means something to them. Air drying or oven bake modelling clay products (suitable only for age over 3 years) similar to plasticine can be used which allow the pieces to be hardened into permanent shapes.

What next?
Once stimulated you might want to demonstrate how to roll a ball and make a sausage of clay and coil it to make a circular shape. Let them experiment making shapes themselves. Once adept at creating coils you might want to show them how to stack the coils to make a bigger shape. Plastic cutters such as used in cookery can be used to cut out shapes from a flattened out clay just like cutting shapes out of pastry.


What about painting colours?
Many of the items once air hardened or oven baked can be painted with acrylic paints. This allows children to learn a painting skill. The use of different size or shape of tip on brushes can help with children of different skill levels or ages. These skills can then be readily adopted and used with ceramic paints as the child progresses to making real pottery.

What about older children?
Older children need more to keep their interest so create a project and set them a challenge of making an item such as a coin tray. The same materials can be used as for younger children.

Alternatively get some real pottery clay and get them used to its feel and how water affects it and allows it to be smoothed or reprocessed when it dries out..  Of course this might become more messy but that's all part of the fun. Learn that large sections of clay crack on drying and why!

Sculpting tools can be used to  allow even more skills to be developed and create a personalisation of the work.

It is important to note that all items produced from the above information should be considered as purely decorative. Under no circumstance should they be used as food contact items.

Real pottery
In order to make real functional pottery special ceramic materials, glaze and colour need to be used as well as firing in a pottery kiln at very high temperatures (greater than 1000C). This requires some specialist knowledge and expertise. Pottery classes would be recommended at this stage to progress in a safe and friendly environment.

Acrylic paints and a domestic oven WILL NOT produce functional pottery.

More information about getting children to work with clay can be found at 'Teaching Tips for clay' Even 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.

Art Deco Ceramics

A time of great design or merely time for a change?

Art Deco ceramics are commonly associated with specific designers such as Clarice Cliffe, Susie Cooper and Charlotte Rhead whose striking designs changed the face of modern pottery. However the term covers a much wider range of pottery styles as well as architecture and fashion. But was it truly a time of great design or merely time for a change? Let us examine the evidence.....

The history of Art Deco

Ravel conical ware by Clarice Cliffe
Photo by Leonard Griffin

Art Deco is said to have begun in France in the 1920s and developed internationally especially in Europe and America until the late 1930's. However it was not until the revival in the 1960s that the term 'Art Deco' was introduced. Until that time it was called 'Arte Moderne' or 'Arte Decoritif'. Since that time many modern potteries have developed patterns based around similar principles.
The advent of Art Deco changed the face of pottery in the UK at the time. The bright colours and geometric shapes of Clarice Cliffe especially, was a long way removed from many of the chinese inspired pottery designs that had gone before. However many shapes and designs were influenced by Mexican and Egyptian styles. A revolution in design was in the making! In the UK the popularity was aided by young new designers and and the advent of advertising and to a degree mechanisation. Designer labels grew as a marketing trend and women designers had phenomenal success. It became a necessity for small potteries to find new designs to beat off the threat of imports from Germany and Czechslovakia and Japan.

Clarice Cliffe

Original Bizarre on Athens Shape
Original Picture by Harvey

Clarice Cliffe, probably the name most associated with Art Deco style, was born in Tunstall, Stoke on Trent in 1899. She joined Royal Staffordshire Pottery aged just 17 and briefly studied art at the Royal College of Art in London. Her skill was such that she rapidly became a top designer of ceramics and was probably the first to design both the shape and decoration of UK commercial tableware. Cliffe produced some of the most exciting designs of the times ware adorned with bright colours such as Original Bizarre.

Crocus pattern
Photograph by  Andy Titcomb

Her success resulted in numerous designs being release in commercial volumes between 1927 and 1939. However it was the more conservative 'Crocus' pattern which was regarded as her signature pattern.
Pieces of Clarice Cliffe are now highly collectable and include such striking designs as the conical ginger sifters. Collecting is made easier by the fact that virtually all Clarice Cliffe pieces are clearly marked with her name using a rubber backstamp or litho.

Susie Cooper

Kestrel pattern
From National Museum Wales

Born in 1902 in Stoke on Trent, she entered the pottery industry at A.E. Gray & Co in 1922 and trained under Gordon Forsyth. Brightly coloured abstract geometrics and cubist patterns were her trademark and she developed some stunning designs such as Kestrel and the cube shape galaxy pattern. By 1929 she had left Gray and started her own pottery painting business and this initiated a long and distinguished design career spanning 60 years. Her designs were highly practical with 'fitness for purpose'being a common theme. A black triangular back-stamp with the words Susie Cooper Productions was used until about 1932. After this time a variety of signatures was used.

Charlotte Read

Tube lined plate by Charlotte Rhead
Photo by Chris Bertram.

Born in 1885 into an artistic family in the potteries town of Burslem, Charlotte Rhead studied art at Fenton School of Art. Working for a local company Wardle and Co she learned the skill of tube lining. It was this skill and the influence of her time at Wood and Sons which set her career apart as a designer. Later in 1926 working for Burgess and Leigh she mainly produced ornamental or luxury pieces using her tube lining skill.

Other Art Deco ware

Shelley Vogue shape cup and saucer, designed by Eric Slater 1930

Harmony Art Ware ginger jar - Eric Slater 1932

The Shelley Family was a highly acclaimed producer of Art bone china in the art deco style. Apart from the elegant 'vogue shape' it produced highly decorative vases such as
'Harmony Artware'. Eric Slater was the designer responsible for many of the hugely successful designs.

The Wedgwood family also produced a range of ware in art Deco style. Using a range of designers such as Keith Murray, Skeaping, Makeig-Jones, and Ravilous they continued to create outstanding designs throughout the 1930's. Makeig-Jones in particular changed the image of Wedgwood ware with her inspirational 'Fairyland Lustre' range of patterns.

The Modern Era

Wedgwood Jasper Conran

Clearly many of the Art Deco designs of early period have inspired post year 2000 patterns. Classic, timeless and elegant, almost all top pottery brands have some element of Art Deco in their range. Wedgwood, Portmeirion, Dudson and Steelite each include high coloured decorative patterns or striking geometric shapes. This is not by accident and I can only conclude that the Art Deco period was truly a time of great design!

I would love to hear your comments?

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.