Instructables

How or where do i make or find terra cotta clay?

ok so i am in nead of terra cotta because i have many projects i would like to do with it 

Clay is found, in some fraction, in many different soils, and there is a simple test for finding out how much clay is present in a given lump of earth. You thoroughly mix up the soil in a jar with water, and then let it settle.  

The clay particles are the smallest, and most easily suspended, and they settle out last.  This is compared to the bigger, heavier particles, like sand, which settle out first.  In fact clay particles are so small, and so easily suspended in water, that it may take a day or two for the clay to settle out the water completely.

A drawing of this soil+water+jar test is attached.  I borrowed it from here:
http://www.sustainableguide.com/articles/article.php?aid=A-4

There may also be organic material, like roots from plants, and that usually floats on top of the water, and doesn't settle.

The reason the jar-test is meaningful, is because it suggests a way of separating raw clay, from the other junk you don't want.   And the same method can be "scaled up". 

Instead of a jar you use a large bucket, or a plastic 40-gallon drum if you've got one. 

You mix your clay-containing dirt with water.  Then let it settle.  Then skim off the floating organic scum, leaves, roots, etc.  Then let it settle some more.  Then after a few days, when the water turns clear, try removing the water, by siphon, or pouring it off.  Then let the remaining mass dry out.  Then, provided the earth you started with had a good fraction of clay in it, this clay layer is on top, and waiting for you to scoop it out.

When it dries out completely, you can break it out in chunks.  The second picture shows a plastic barrel containing settled, dried-out clay, in my garage.

soil-jar-test--sand-silt-clay.jpgplastic-barrel-with-clay.jpg
Sweet technique, thanks for posting this!
connoboarder (author)  Jack A Lopez3 years ago
oh thank you that is really helpful!!
orksecurity3 years ago
It's a natural clay. Find a deposit in the ground, or buy it from someone who has done so.

It isn't all that expensive. One example of prices -- this isn't a recommendation because I've never dealt with them -- would be http://www.sheffield-pottery.com/Earthenware-Ceramic-Clay-s/30.htm
connoboarder (author)  orksecurity3 years ago
i was thinking more primative...but thankyou anyway
rickharris3 years ago
You don't say where you are, or your experience or what access to equipment you might have. All these would help us answer.

+2 on all above. As an addition IF you can find or make a large block of plaster of Paris you can use this to dry the clay - Pull up a BIG handful of wet soggy clay and push back and forth on the plaster block until the water is dried out and the clay is the required consistency.

Most people either live close to a pottery supplier OR can get their supplies through the internet - unless your on a very tight budget and or want to be very primitive.

We live on white clay deposits not too far down -
caarntedd3 years ago
I remember doing this as a school kid.

Dig up some clay. Put the clay lumps into a bucket of water. (This works for wet and dry clay as long as it has not been fired in a kiln, and is a good way to recycle unfired pots that may not have turned out the way you wanted). Let the clay soak until it is a smooth gooey consistency. (This could take a few days or more).

Filter the goo through some fine mesh or some sort of cloth to remove small stones etc. It may need a few passes. Trial and error.

You need a frame of some sort for this step. You can make one from timber (like when making mud bricks) or I made a "frame" out of bricks (just 3 bricks long and 2 bricks wide arranged in a rectangle) sitting on the ground in a shady spot.

Lay a large enough piece of cloth inside the frame so that it hags well over the edges, and pour the goo into it until your frame is full. Then fold the cloth over the top of the goo, and sit a timber board or something similar on top to hold everything in place.

Now just let it dry to the required consistency over a few days (depending on the weather) and check it often so it doesn't dry out too much. When it is right, slip your clay block into an airtight plastic bag and store in a cool place.

 As far as I know you can redo this as many times as you like with your old dried out clay and will still be useable.

Happy potting.
The hard part is the first one: finding clay to dig up.

(The one time I found a small deposit, it was actually pretty good as it stood. I'm sure that if I'd tried to dig out more I would have had to work harder at purifying it.)