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..

Digital printing of ceramics

Digital printing of ceramics and decals

Digital printing of decals and ceramic tiles is already well established. Computer generated images can be printed directly onto ceramic tiles via special inkjet systems. Alternatively a photocopier type system can be used to print onto decal paper. Of course both these systems require special machines and ceramic inks or toners to produce optimum results. Nevertheless these systems are causing a revolution in the ceramic tile industry.

The detail of decal printing

Ricoh desktop ceramic printer

In the case of digital decal, you can either create a drawing or photograph and then convert it to a digital image suitable for printing on to decal paper. The image is produced as a decal by a photocopier type machine. After printing the image is sealed to the paper with a covercoat and allowed to dry. The decal can then be applied in the same way as conventional decals by a water slide method. Decorators have the choice of either outsourcing decals (small quantities) or for large quantities buying a machine and toners and printing themselves..

The detail of ink jet printing of tiles

Pigment	System	Temperature	Colour
Yellow	Zr-Si- Pr	1250 °C
Red Magenta	Zr-Cd-Si-Se	1250 °C
Cyan	Zr-V-Si	1250 °C
Black	Fe-Cr-Co-Ni	1250 °C
Primary 4 colours used in ink jet printing

In the case of ink jet printing, the digital image is converted to a ceramic image using a specially adapted ink jet printer and special inks. The ceramic tile passes beneath the printer head and the ink jet colour nozzles deposit the image on the tile.

Gamma Ink Jet Tile Printer

Typically up to 10 ceramic colours are used to produce high quality digital images, 4 similar to the primary colours shown above plus additional spot colours. Browns, coral reds and white are commonly used to fill gaps in the colour space. Special printer heads are used to cope with the highly abrasive ceramic inks. For maximum definition and colour intensity special glazes are sometimes used as the base for printing the coloured image. The printed item can be fired almost immediately after drying.

3d Printing of Ceramics

I am constantly amazed at the ceramic challenges I see each year. Whilst making pottery and ceramics is an ancient tradition, new industrial processes and products (or the re-introduction of many older techniques) continue to stretch the imagination.

3d printed sugar bowl

Both in the UK and USA, 3 dimensional digital printing is one such technique. Developed initially for rapid prototyping of plastic objects it is now being used for small special ceramic parts. The potential to build up a ceramic mug  layer by layer  from a computer image is certainly feasible.
 I have seen the initial prototypes which have been glazed and fired. Many technical challenges remain for this process to be viable commercially but I have no doubt that in the long term this will happen.
For more information about this technique see the link project below:-
 University of Bristol project

3d printing using liquid clay syringe

3d extruder printing

This type of printing is also in the early stages of development for ceramics. Many questions remain particularly control of rheology and removing air pockets and machine development.. However the picture on the right shows how the process works. An air powered syringe forces liquid clay out of the nozzle to build up the object in layers. The head could be computer controlled to map out a digital design.
Potentially the ceramic designer can be creative in designing complex forms as well as simple shapes.
Picture and link to more information kindly provided by Ceramic 3D Extruder (FabLabZuidLimburg) / CC BY-NC 3.0

So what does this mean to the hobby or studio potter?

The opportunity to make low cost efficient designs which can be personalised to meet your customer needs. Digital ceramic decals are already established and widely available. But keep following the progress of 3d printing as the potential is endless. Perhaps now is the time to look at ways these techniques can expand your opportunities?

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.

Shiny Pottery Without The Glaze!

Roman red gloss terra sigillata bowl with relief decoration
Photo from Museum Römerhalle Bad Kreuznach

Terra Sigillata

After reading about burnishing recently I researched the technique even more and came across Terra Sigillata which literally means 'clay with little pictures'. This definition makes sense if you look at many of the early pots made using this technique which feature figures in relief. However later pots similarly described do not contain figures. So Terra Sigillata has come to be known as pottery manufactured with surface slips which when fired produce a glossy surface ranging from a soft lustre to a brilliant glaze-like shine. Samian ware is also sometimes used to describe all varieties of terra sigillata including undecorated ware.

The history

Ancient Greek pottery neck amphora showing a swordsman.

Image Courtesy of Marie-Lan Nguyen

Most well known for its use in ancient Greek ware Terra Sigillata now describes specific types of plain and decorated tableware made in Italy and in Gaul (France and the Rhineland) during the Roman Empire. These vessels have a range of glossy surfaces and are often found in their characteristic colour range of pale orange to bright red.They were produced in standard shapes and sizes and were manufactured on an industrial scale and widely exported.
The sigillata industries grew up in areas where there were existing traditions of pottery manufacture, and where the clay deposits proved suitable. The products of the Italian workshops are also known as Arretine ware, and have been collected and admired since the Renaissance.

What is a Sigillata slip made of?

Refined Kaolin particles

Terra Sigillata, is made up of finely separated clay particles in water. The clay particles are mostly composed of kaolinite crystals which have a flat plate-like structure.  These particles therefore have a high width to height ratio, called the aspect ratio making it easy for them to fit together in a stack just like a pack of cards.The platelet however are tiny and at less than 2 microns wide can only be viewed using at high magnification microscope. To put this in perspective a human hair measures approx 70 microns in diameter-35 times the size!.

How Does it Work?

When the slip is applied to the surface of a clay article as several very thin layers, the flat plate-like particles align naturally to give a smooth reflective finish. The application process is critical as applying one thick layer is likely to cause the layer to crack as it dries and shrinks. The slip can be successfully applied to leatherhard or fully dry clay. However the best results are reported as being by applying to it to dry ware that has had the surface roughened using 120 grit sandpaper.

For a shinier appearance a quick polish of the surface with a piece of chamois or plastic film or even with a finger tip is effective. This increases the fraction of platelets laying flat on the surface thereby creating increased reflected light.

How does this differ from burnishing?

Polishing and burnishing can give a highly reflectively surface finish but it is a highly labour intensive process. It requires the potter to compress the clay with a polished rock or the back of a spoon in small circles for hours on end until the whole surface has been compressed. This process causes  the clay platelets on the surface to lie flat, while all the other coarse particles are pressed down into the surface. However it creates a very smooth, highly reflective surface.

In contrast, Terra Sigillata avoids the laborious polishing process by naturally laying down a thin layer of aligned clay platelets. Minimal polishing is required to achieve the same high shine as hours of burnishing.

Making the slip

You can make terra sigillata slip from almost any raw clay or clay body that contains kaolinite. However, only a portion of the starting material will contain sufficient fine clay particles to make a good Terra Sigillata. It is therefore important to use a separation process to split the 'good' clay from the 'bad'. This involves first mixing the clay then allowing it to sediment before decanting off the good material.The yield and performance of the slip will be influenced by the particle size of the clay. Therefore in general finer starting clays produce better slips and yield.

Details

The first step is to make a highly fluid de-flocculated suspension of the clay of SG 1.15. A mix of sodium silica/soda ash deflocculant and water is used. After sedimenting for approx 20 hours the ultra fines are decanted off to be used to produce the slip. The suspension at this stage is very watery and needs to be concentrated by evaporation or gentle heating of slip. Approximately 10% of the initial starting material suspension will remain to be used as slip.The slip needs to be approx SG 1.15 for best application.

Applying the slip

Application is made to the dry clay body by using a wide, thick soft brush heavily loaded with slip. Long flowing strokes should be used and drips should be avoided. if a drip appears remove it immediately with your brush. Work around the piece, building up thin coats until I the surface begins to conceal the sanded texture. If available a potters wheel can be used to give an even application. Overall, it needs a very fine coat of slip to avoid cracking and peeling of the layer.The success of this process is a matter of experience-as different slips require layer thickness for optimum effect.

Polishing of the applied Slip Surface

As soon as the the slip layer looks touch dry the surface is polished with a piece of grocery bag plastic or soft material. Amazingly the surface should develop a bright shine in just one polish.

Firing of the slip applied ware

Like burnishing, the terra sigillata surface needs to be low fired for best results but this depends on the clay slip and the underlying body used. Whilst a true burnished surface is recommended for firing at less than  cone 012 (875C), a terra sigillata-coated surface lightly polished can sometimes be fired as high as cone 02 (1125C).

Red terra sigillata also changes colour as well as gloss as the temperature is increased. Starting with orange red then brick red, it will finally turn red-brown before fusing due to the high iron and flux content.

Other clays like stoneware, ball clay and china clays will give white to a light tan depending on their source and chemistry.

Colouring of the Terra Sigilatta

Fine oxides or finely ground ceramic stains can be mixed with the slip to create a wider range of fired colours. However in general the greater the addition of stain the lower will be the gloss on the finished product. Best practice requires the stains to be thoroughly dispersed using a ball mill process. However very finely divided oxides like copper carbonate or cobalt carbonate can be added in small quantities without significant loss of shine.

Summary

Clearly the making of Terra Sigilatta is a skilful but labour intensive process. The decanting process is critical to obtaining the highly decorative glossy finish. However the quality of finish with the soft buttery feel is worth the effort. Indeed many alternative effects have been  obtained using the sigilatta slip in underglaze or combination with other potting methods. It still amazes how the ancient potters developed such sophisticated pottery effects over 2000 years ago. Modern pottery continues to learn from the past by application of our  greater scientific understanding! Long may it continue!

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.

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.

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.