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.

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.

Starting out in Pottery? Read this first!

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

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

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

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

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

Start with a pottery class

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

Choose a Quality Clay and Glaze supplier

Clay Body

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

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

Process the clay and glaze as recommended by the supplier 

Orton Cones

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

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

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

Only once skilled add your own artistic flair

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

Developing  your own style and delight in making something unique

Lori Duncan Raku

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

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

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

Keep on learning and enjoy

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

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

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

Above all enjoy!

Good Luck
Happy Potting
The Potters Friend

Burnishing unfired clay pottery

Burnished ware by David Greenbaum

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

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

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

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

 So What is Burnishing and how is it done?

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

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

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

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

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

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

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

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

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

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

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

How to Choose a Pottery Class

The Benefit of Classes

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

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

Be clear on your needs

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

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

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

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

Choose the right teacher and class

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

Some helpful links

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

Good Luck and enjoy!

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

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

Details of UK pottery classes

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

How To 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.

Raku Pottery

What is Raku Pottery?

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

The process in brief

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

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

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

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

The Process in detail

The Clay body

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

A typical body recipe might include by parts weight:-

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

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

The Glaze

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

Raku (glaze) firing

Northern Kilns Raku kiln

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

Types of Raku kiln

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

The Reduction Process

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

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

Safety

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

Top 10 Pottery Making Tips for the more experienced Potter

Pottery making is a fun but sometimes frustrating hobby. You never know exactly what your results will be when you open that kiln door! Here are my tips to make pottery making that little bit more rewarding......

1. Keep records of everything you do-that way you learn quickly and can repeat your successes and avoid your failures.

2. Label your buckets not your lids- don't learn the hard way that you have just glazed your speciality piece in the wrong glaze!

3. Buy a kiln with a modern controller. Modern controllers are now relatively inexpensive and give you such freedom to control the firing in a way that best suits your product.

4. Keep drying of your product consistent. Drying too quickly is one the most common causes of glaze or clay faults.

5. Learn something about the materials you use. Armed with a little knowledge you can save so much time.e.g. Does glaze go off? What happens to my clay if it freezes?

6. Keep your clay in good condition by covering it with plastic when not in use. That way it retains its plastic condition.

7. Plaster moulds need to be replaced after 40-50 casts. It is false economy in slip casting to continue to use old moulds. These may give inconsistent thickness, pinholed ware and much more besides!

8. Use Orton cones or Bullers rings in your kiln. That way you know your kiln is performing OK and you can spot potential problems such as element failure before they become disastrous.

9. Give some pieces to your loved ones or to charity. The feel good factor will keep you motivated.

10. Continue to share your passion with others. Go to pottery classes and learn something new or join an online pottery group.



Alternatively why not test your pottery knowledge with my quick pottery quiz

More information and other technical articles on pottery and ceramics can be found at my website www.pottersfriend.co.uk

Go now to sign up for my free newsletter.

What is a glaze?

A mature pottery student recently asked me the question 'What is a ceramic glaze?' I hesitated whilst contemplating how to answer what initially seemed a very simple question. In the end I gave him 2 answers , a non technical one and a technical one. The precise amount of information he required depended much on how he wanted to use the information.

Sometimes too much information only leads to confusion!

For example an evening class student wanting only to paint pottery and later have it glazed and fired by an established potter needs only basic information.

In contrast a student studying pottery making and ultimately wishing to make and fire his own glazes needs a much more detailed chemical approach.

The Answers

These are the answers I gave him:-

1) A pottery glaze is a glassy coating applied to the surface of a ceramic to create a smooth, impervious, and decorative finish.

2) A pottery glaze is a mixture of ceramic materials which may often include minerals such as felspar and silica, a glass like component such as frit, clay as a suspending agent, and pigment as colouration. Many other minerals or oxides may also be used. These materials are finely ground in water to produce a glaze slip. Other organic and inorganic additives may at this stage be added to aid application. The slip is then applied to the ceramic body and fired to a sufficiently high temperature for the components to physically and chemically react to form a smooth glassy coating that bonds strongly to the body. Normally a temperature in excess of 1000C is required.

Do you have any simple questions you want answering? Please let me know.

More information on pottery making can be found at my website The PottersFriend

Pottery Clinic

Glaze blister at high magnification

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

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

I look forward to answering your questions