Sourcing Clay // how and why
When it comes to choosing the clay I work with, there are a few practical factors I consider and a wide range of options to choose from. I could dig up clay and really take it back to basics; however, that approach is not always suitable for everyday use, so it doesn’t inspire me when I aim to make pieces people can enjoy and use for a lifetime. This choice is personal to each potter and depends on the intended function of the pottery being made. Wild-sourced clay is wonderful, and if it tickles your fancy, then I say get out there and dig! When I am sourcing bags of clay from a manufacturer or a ceramics supplier, the first thing I do is research the company and the specific clays they offer. There are several questions I endeavour to answer that reveal whether the clays and the company are a responsible, ethical and sustainable choice for my work.
The 3 questions I feel are most important are:
What are the raw ingredients?
Where are they coming from?
How are they produced?
I know from asking and digging that little bit deeper that the main clay I use is made up of:
Fireclays and marls from South Staffordshire and Shropshire
Ball and china clays from Devon & Cornwall
Grog from Cheshire.
I also know that it is a panmilled body, which demands considerable skill and experience from the operative to produce. The raw materials are blended in specially adapted panmills, machines that in a former life were used for blending chocolate at Cadbury’s, and are now repurposed for this precise, artisanal process. i love knowing this little fact!
Understanding where my ingredients are mined and produced is always at the top of my ‘must know’ list, and it helps me determine the most sustainable option for my practice. Because I live in the UK, I tend to favour materials that have not been imported from distant countries — not only to reduce the carbon footprint associated with long-distance transport, but also to be confident in the ethical standards and labour practices involved in extraction and supply.
Basically, importing raw materials from abroad is often cheaper than sourcing and extracting them within the UK, but the mining standards in some countries can cause serious harm to people, animals and the environment. Read my glaze-making post for more about that. Unfortunately, it’s common practice to withhold the ingredients’ origins, and they are not printed on the packaging or included in the product descriptions. I have to contact suppliers directly — and not all of them are willing to disclose that information.
The clay I predominantly use, and will use as an example here, contains Ball clay and China clay sourced from Devon and Cornwall. Most pottery clays include Ball and China clay in their mixtures, and you can also purchase these materials in raw form if you want to make your own clays or glazes. Both China clay and Ball clay are mined internationally as well. Through ongoing research and asking questions, I have learned how to identify where particular ingredients are mined. If you want to buy raw China clay or Ball clay, there are many types to choose from; the specific mining locations are not always stated explicitly, but the labels and terminology they use can be interpreted if you know what to look for.
For example, I now know that EPK China Clay is mined in Florida, whereas Grolleg China Clay is mined in Cornwall, and Hymod Ball Clay is mined in Dorset, or Hyplas Ball Clay is mined in Devon. It really is a MINED_FIELD!
Imerys : St Austell, dry mining plant in Cornwall.
I suppose what I’m trying to show is that making sustainable choices as a potter takes quite a bit of knowledge and effort, even when it’s as seemingly simple as sourcing a bag of clay. Even if I were lucky enough to have a charming ceramic supply shop within walking distance of my studio, that convenience alone wouldn’t automatically make it the most sustainable option for me. Yes, the reduced personal carbon footprint from fewer trips would be a real benefit, but the clay itself might still be imported, and I would need to take the extra steps to confirm whether it has been sourced and produced responsibly.
As an individual maker, it’s important to me that any pre-made clays I use have been carefully researched and come from a reputable, trusted source.
I do this because I don’t want it to have a massive carbon footprint or for my main material to be full of ingredients that were mined unsustainably, disregarding human rights, or contributing heavily to global greenhouse gas emissions. So I ask questions of anyone willing to answer them — which can sometimes annoy suppliers — but I do it anyway, because responsible choices matter to me and to the future of the craft.
Doing your own research
If you're a potter and you're thinking about approaching your clay supplier to ask a few of your own questions, it's useful to understand the difference between a manufacturer and a supplier.
A manufacturer is a company that produces clay on site, sells it directly from their own website or shop, and provides their pre-made clay bodies to other suppliers. They may also list and sell products from other manufacturers on their own site or in their shop, which can, of course, be a little confusing.
A supplier is a company that imports and distributes pre-made clay bodies from a number of manufacturers from their own warehouse or shop directly. Therefore, to get technical information about a clay body, it is usually best to ask the manufacturers themselves, as most suppliers will only hold basic product details. To begin your research, explore the websites of the suppliers and manufacturers you are considering buying from; you should be able to find out how long they have been in business, whether they are family-run, and whether they distribute throughout the UK, Europe and/or worldwide. You can then decide how much you value those factors.
Digging a little deeper, what you really want to discover is the origin of the raw materials used in the clay and where and how the clay is processed and formulated. With so much to choose from, it is sensible to select a clay that suits your intended function, then contact the manufacturer personally to find out what’s in it and where the components come from. Understanding that a UK manufacturer will either produce or outsource the materials and then use machinery to mix them and create their own signature clay bodies gives you useful base knowledge.
Information about the exact manufacturing process and ingredient lists is not readily available on most websites, and what you do find is often not very detailed. However, in most cases, if you ask the right questions of the manufacturer, you will get the answers you need. Having a clear comprehension of these practices is of great value to any potter who wants to be responsible and make informed, conscientious choices.
The production of pre-made clay
The industrial production of making clays has been around for about 100 years and has developed through many refinements. All pre-made clays are made up of a carefully formulated recipe, and different methods are used to blend the raw ingredients, add the correct amount of water and then pug the mixture to create the desired consistency. The two most widely used approaches to produce clay bodies in commercial settings are the traditional slip house method and the panmilling method.
The slip house method begins with dug clay being placed into large vats of water called blungers. At this stage the clay is thoroughly mixed to create a smooth slip. That slip is then passed through a series of sieves and magnets to remove any foreign or coarse particles. This is an important step because the raw clay often contains a variety of impurities from the ground, such as stones, coal and other debris, which could cause issues during shaping and the subsequent firing process
The next step of the slip house method is to remove the excess water in a machine called a press filter. The machines have a special cloth inside that has been designed to allow only water to pass through it.
The clay is pushed against the cloth to remove the water and create solid slabs of plastic clay known in the industry as cakes.
The final step is pugging to form the finished clay for use. A pug mill is a simple extruder with blades that cut and compress the clay, feeding it in at one end and forcing it out the other. It is at this stage that grogs and sands are also blended in to adjust texture and performance. Unlike smaller studio-sized pugmills, the machine’s exit point is sized to produce 12.5 kg blocks, which can then be cut at the correct point, bagged and prepared for sale to a supplier.
The panmilling method is not as widely used these days; however, it remains one of the best approaches for mixing highly grogged or flecked clays. Rather than adding clay to a vat of water, water is poured into a revolving pan containing the dry materials; this action mixes them together and forms lumps of clay that are later pugged and bagged. Some manufacturers consider sustainability part of their core business practices, while others do not prioritise it when making material choices. So ask them, and support those who do.
To wrap this up — as I could keep waffling on forever — if you’re a potter wanting to make more ethical and sustainable choices, start by asking your clay supplier a few questions: find out what’s in the body you use and then research those ingredients.
If you’re a conscious consumer of pottery, be aware that many ingredients can be unethically sourced, including the clay itself; even if a piece looks gorgeous or the maker is charming, it’s reasonable to ask about the origins of their materials.
