Unless you are familiar with natural clay, it would be a good idea to take a small sample. In a short period of time, you will be able to determine whether you have collected sand, mud, clay, or likely some of each. If your test yields a very low percentage of actual clay, you may need to examine your collected soil area for a better source.



Gather a good handful of what you are confident is clay, and process it in one of the following ways:



1.) Collect a chunk of clay, allow it to dry, smash it into small chunks, then soak.

See step #6 for detailed instructions.



2.) Toss the entire chunk into a bucket of water, stir on occasion to break up the clump

See step #5 for detailed instructions.



No matter which step you choose, only a sample is necessary. You don't want to gather a lot of material only to discover you've collected nothing more than mud.



In the photo shared in this step, you will see what looks like a glass of leftover iced coffee that sat out overnight.





Note the layer at the very top, which is water.

In the middle, a thin strip of valuable good stuff, called Terra Sigillata, which translates to 'sealed earth'.

For ease of reading, it will be abbreviated as terra sig or terra from here.





Bottom layer - clay, sludge, and other sediment. This is the layer we will harvest for workable clay.



In this step, we will address the both the bottom layer, and also the middle layer, which is basically a wonderful suspension of the finest clay particles. This slippery liquid is very useful as a glaze, and depending on the clay body, can produce a glossy, or even a satin finish. If you are experimenting with harvesting your own clay, I highly recommend dabbling a bit in using your own terra sig, even if only for the experience. For a wealth of information regarding this wonderful by-product of harvesting your own clay, I highly recommend a visit to Ceramic Arts Daily



If you wish to collect a bit of Terra, use a turkey baster to suction the water from your test sample, which will expose the next layer of Terra. Use the turkey baster to gently suction only the Terra from the sample, and transfer it to a jar with a lid. Baby food jars are perfect for storing terra. Save until you are ready to glaze an item which has been previously fired in a kiln.



Once you determine if you like the finished look of an item glazed with sig, you can collect even more, as it stores well when kept sealed.



Once you have remove the first two layers, water and terra sig, the 'good stuff' is at the bottom. Put your fingers into the bottom layer, and you will be able to feel the thickness, compared to the previous two layers. If you do not feel anything thick that resists your fingers, you may need to go back to the collection site and try again.



Not up to trying to make your own? You can actually order TERRA SIGILLATA from The Ceramic Shop