Pottery and the colour Blue

Royal Blue

The History of Blue and White Pottery

Blue is one of the colours of the rainbow and it has become associated with many things over time. Perhaps the connections with the sky and the seas are the most strong. However it also been used to denote cold, loyalty, truth and conservatism. In past eras the blue coloured pigments for clothing were scarce and expensive leading to the colour being related to wealth and royalty eg Royal Blue. It is a colour that is not available as a natural ceramic pigment but needs cobalt ore to be refined to produce the highly intense blue colour. In the early days the ore was roasted and then further melted with a a glass to produce the early pigments of Zaffre and Smalt.

The origins of blue colour in pottery are a little confusing.

Ming Vase

The Egyptians are known to have been making blue coloured pottery since before 400AD but it was the Chinese cobalt blue and white pottery from the the Tang Dynasty onwards that led to a huge interest in blue and white in Western Europe. The introduction of tea to England escalated the interest in pottery tea sets especially blue and white.

Cobalt has been the source of pigments for English blue and white pottery since the eighteen century and these were the pigments used to make the famous Spode patterns of Willow and Indian tree. Since that time blue and white has never disappeared from our lives.

Blue and white in the 21st Century

Now old designs such as Burleigh compete with more contemporary blue patterns in our High St. Denby Imperial blue has stood the test of time being unique in colour, texture and appearance. Similarly, the English style of Burleigh ware created by the unique hand made tissue printing technique continues to attract buyers from around the world. New patterns like Blue Hydrangea from hand made producer Peregrine pottery continue to gain interest from those looking to buy English style with a modern look.

Blue Hydrangea from Peregrine Pottery

Burleigh ware

Denby Imperial Blue

The Pigments

Although modern blue ceramic pigments started with Zaffre and Smalt, their development has continued and modern day pigments provide high intensity with the ability to meet specific colour tones or firing temperatures. Whilst the use of the basic cobalt oxide in glazes is still common for craft or studio glazes looking for a low cost, the use of cobalt silicates and cobalt aluminate pigments has flourished. They extend the inter-mixable nature in glaze or coloured decoration and often provide improved dispersion characteristics. Some examples of the colour tones available using the different pigment types can be seen in the table below.
(NB Web colours are never an exact match for ceramic tones)

Colour name	Colour pigment	Colour shade
Matte Blue	Cobalt aluminate
Mazarine Blue	Cobalt Silicate
Royal Blue	Cobalt zinc silicate
Willow Blue	Special
Azure	Cobalt alumino-silicate
Flow Blue	Na-Ca-Cobalt silicate

Where next for Blue and White?

Whatever your interest blue continues to feature in pottery decoration across the world. I predict this fashion is unlikely to change soon. I would love to hear whether you agree and your thoughts on blue and white and why its appeal continues so strongly?

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

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Should I make my own Pottery Glazes?

Coloured glazes used by Tinkling toadstools

This question has caused a lot of debate among potters. It is a similar question to "should I make my own bread, cakes or pastry?" Clearly there is no right and wrong answer. People who bake their own bread and cakes do so for numerous reasons. Whether it is to reduce costs or make it fresh or make it taste better; all are valid reasons. However most do it because they like it and the self satisfaction it gives them to create something of value.

 Similarly, the potter will often claim that making glazes gives him the same type of satisfaction, is cheaper and gives him more scope for creativity! But lets look at the issues involved in making glazes in detail to see if his claims are true:-

 Costs

Glaze materials

There is little debate that buying the glaze materials to make the glaze can reduce costs significantly. Common materials such as clays, felspars, silica, frits and pigments are all readily available from a number of suppliers. However, often they are not in the ideal form to produce a glaze without additional processing. Most need at least a number of processing steps to make a satisfactory glaze. These steps include, preparing a recipe, grinding or mixing with water, sieving, magneting, testing, and controlling the glaze slip consistency using additives. The time and knowledge to correctly process and test the glaze are mostly overlooked when cost comparisons are made. For those with time to learn about glaze materials and the process this is not an issue. However for many hobbyists who are time poor it clearly does not make sense economically.They are better using reliable commercial glazes.

Creativity

Unique copper ruby glaze

Without doubt making your own glazes is a creative exercise. Again using the same cake making analogy as before, you have complete control of the make up of the glaze and how it will look after firing. Just like cake recipes there are thousands of recipes for glazes each giving its unique colour, texture and appearance depending on how its fired. This uniqueness is what many studio potters strive for.  By varying the pigments and make up of the glaze in theory you can innovate to your hearts desire! Therefore creativity can surely be improved by making your own glazes!

Technical restrictions

In practice, however,  there is considerable science behind making acceptable glazes:

• The glaze needs to technically match the body or the glaze may just peel off like old paint. 

• There is a limit to the range of compositions that can be made- for example some recipes will just never make glossy glazes.
  
• The firing cycle and atmosphere have as great an affect on the glaze appearance as the recipe.

The fired glaze surface of functional tableware needs to pass the requirements of legislation e.g. toxic metal release into foodstuffs.

So if you want to be creative with glazes you also need to have some technical knowledge. Potters without a scientific background may struggle to understand these technical parameters and hence making glazes could ultimately become more trouble than its worth.

Health and Safety

Unleaded Glaze

In recent years this issue has grown in importance for potters making their own glazes. Lead, for example, is being phased out in commercial glazes and its use and safety has been severely questioned especially in the USA. Other materials such as Barium compounds need to be used within strict guidelines for safe use. Even pigments such as cobalt and nickel oxide have been questioned over their safety. Clearly there is a lot to learn technically to comply with health and safety during the making of glazes. These issues are understood by commercial glaze manufacturers who can provide up to date data sheets on the glazes they manufacture and supply.

Equally important is an understanding of the legislation that applies to the fired product to meet the demands of the end market. Functional tableware has to meet much more legislation than ornamental ware in the various countries around the world.

Summary

In summary making your own glazes safely and successfully is much more difficult than at first appreciated. Technical and health and safety issues are not easy to overcome. However for a potter or hobbyist with a scientific understanding he can indeed be more creative and lower some material costs by making his own glazes. For the uninitiated it will be a long road of trial and error and frustrations. For those determined to try I recommend you do some reading and preparation online or in the wealth of books available before you begin. 

Good Luck and 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.

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.

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.

Opacification of Glazes

Glaze opacifiers are materials which when added to a glaze change the level of transparency of the glaze. Glazes are often described as clear/transparent or opaque. In order to achieve color tone and hide the body color it is often necessary to add opacifier particles which stay discrete in the glaze after firing. Materials which have a significant difference in refractive index from the parent glaze produce the most effective opacification. To the right you can see the effect of adding an opacifier to a transparent glaze. It becomes whiter and milky (opacified ) in nature and flows less.

Below you can see the effect of adding opacifier to a transparent glaze containing different colored pigments

Top = transparent glaze            Bottom = opaque glaze

Typical glaze opacifiers are zircon (zirconium silicate), tin oxide, and titania (titanium dioxide). 

Zircon opacifier powder

Zircon

Zircon is the preferred opacifier for glaze due to the low cost, inertness and stability in glaze. To achieve full opacification, the opacifier content and the particle size are important factors. For addition of zircon to the glaze mill during grinding a particle size of 95% less than 3 microns and a content of 5-10% ensures sufficient opacifier is dispersed to create optimum opacity.  

However an exceptional level of opacity can be achieved by pre-melting the zircon into a glass (called frit) and then using the frit as part of the glaze recipe. These frits are transparent before firing but crystallize zircon during the glaze firing process to give a high level of opacity. 

Tin Oxide

Tin oxide has historically been used as a glaze opacifier but its high cost has limited its recent use to low temperature majolica or special effect glazes. At a level of 5% in a transparent glaze a high level of opacity can be achieved. Its lower solubility in glaze compared to zircon means that lower levels of tin oxide can be used to create the same level of opacity as zircon.. Tin gives a slightly blue white tinge and also has a lesser effect on the glaze appearance than zircon which increases glaze viscosity during dissolution.One major drawback of tin is it reactivity with some oxide pigments. For example, with chrome oxide a pink discoloration may result from the formation of a chrome-tin spinel crystal.

Titania reactive glazes

Titania

Titania is also a very costly opacifier and is used primarily where reactive special effect glazes are required. Like zircon it has a higher solubility than tin in the glaze and even at levels of 4%  tends to give a yellow tinge to the glaze after firing. It readily reacts with other materials in the glaze to create many unusual crystalline phases on cooling.This is ideal for special effect glazes but undesirable for standard opaque glazes.

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.

Go now to sign up for my free newsletter.

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 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
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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.