Why It began with a handful of clay picked up on a walk in the Purbecks. And reading the autobiography of a local potter Guy Sydenham who dug his own clay. But really it started when I was a child digging holes in the back garden. Connection to place - memories - sustainability - tradition
What is Clay?
Clay is one of the main ingredients of the earth’s crust. It is formed over millions of years and has existed for millions of years. Some of the clay deposits close to me are from the Eocene period, which is around 45 million years old.
Clay was originally igneous rock such as granite that has been eroded over time. Often there is a period after which it will have been submerged underwater. It may well be layered with sand and silt.
Clay is made of several different minerals, which can vary a lot, but mainly alumina, silica and chemically bonded water. It will likely also have other trace minerals – the main one being Iron which can colour the clay red, yellow and even green. If you find white clay then you are very lucky.
Clay can be found almost anywhere. Wild clay is simply any clay that has not been dug from an industrial pit, but found out in nature (or your garden!). It can be on the surface (think of a muddy squelchy field you walked through) or beneath (as in your garden when digging a flowerbed). You can look online for geological maps – this site is helpful.
It is ofen found close to water; rivers – lakes – and shoreline – but do be mindful to not take it from an area where it may disrupt the integrity of the land such as a riverbank.
A small sample is ok to claim, but any more you should legally ask permission of the landowner. Always be resepctful.
Is it Clay?
Coil test – make small worm of clay and wrap around your finger – If it crack and crumbles then it’s either not clay or doesn;t have enough clay minerals in it. Clay will be sticky and squdgy when it’s wet, and soft and plastic when a bit dryer.
You can just use it straight from the ground, if it is already soft and maluable (i.e. has water in it). However it may contain plant matter or stones that could cause problems later down the line when you fire it.
Processing your win will be a little time consuming, but in my opinion worth it. First dry the clay completely. It may be helpful to break it into small pieces. Put it in a bucket and submerge with water. Leave for a day or two to fully absorb the water. I use a battery drill with a paddle tool to mix it. Next screen through a sieve to remove large impurities. Then your clay needs to be dried out to be usable. This can be done by spreading the slip out on a plaster batt, or a wooden board.
Once firm enough, wedge the clay to bring it together. You have some wild clay ready to use.
The next stage will be to test your clay. This means firing it. All clays behave differently, and can change quite dramatically when fired. The maturing temperature of clay varies from earthenware to stoneware. Underfired it will not vitrify, and be porous or even crumbly. Overfire and it will blister and melt. You can also mix different clays together in small percentages to get varying results.
Create small pinch bowls, and also little test tiles. You can mark the back with a ruler to see what the shrinkage is which can be helpful. You can also keep in a liquid state to use as a decorating slip. Dry to a powder to add to glazes.
There are some great books written by potters generously sharing their wealth of knowledge and traditional ways. Below is a list I found incredibly helpful a starting point.
Miranda Forrest – Natural Materials
Brian Sutherland – Glazes from Natural Materials
Matthew Blakley – Rock Glazes
Suzanne Straubach – Clay (a history)
Also special thanks for Grace Jones and her PHD