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

Sources of materials

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

Borax granules

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

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

Materials for body making

Body materials

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

Materials for glaze making

Frit granules

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

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

Materials for decoration

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

range of onglaze decorating colours

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

Range of ceramic stains

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

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

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

Summary

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

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

Comments welcomed?

Happy Potting

The Potters Friend

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

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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.