Clay

What is Clay?

Clay is amazing! when combined with water and mixed well it can be plastic and flexible, capable of being shaped into a variety of forms. When dry it can become hard and keeps its shape. When heated up and cooked to higher temperatures it changes its structure and can become hard like rock. It can make hard beads and tools, as well as holding water and making cooking pots, cups and dishes.

Some Basic Terms

Clay - is an earth that is often red, tan, or grey and is notable because it is both sticky and stiff. When wet it can be formed into shapes and dried and heated to make things like bricks, pottery and ceramics

Ceramics - stuff made out of clay that has been hardened by heating.

Pottery - Both the act of making, and the things made by forming clay.

Firing - The way that you heat harden clay into usable ceramics. At 1100 degrees all of the water that is bound in the clay is driven off, and the clay makes a total chemical change so that even if soaked in water it will never go back to being mud.

Plastic/ plasticity - the quality of being able to be shaped and molded without breaking.

Earthenware - Clay that is still semi porous after it is fired. This clay fires between one thousand and two thousand degrees Fahrenheit.

Stoneware - A type of clay that fires above 2000 degrees Fahrenheit, and has vitrified, a word that means that the surface becomes solid and non porous.

How to Find Clay

Clay is heavy fine particles of a few different minerals. Some common clays are Kaolin, Smectite and Illite. These minerals form because of tectonic movement like volcanoes and geysers. Clays form when water gets trapped in minerals where there is also a high content of silica. Clay is recognizable because it is plastic, which means that when you mix the powdered clay with water it can bend and form without falling apart.

There are two kinds of clay that you are likely to find. The first is called Primary clay. This is clay that is going to be exactly where it was formed in the earth. Places that you might find primary clays are: near tectonic events, hot springs, earthquakes and other places where the clay formed. Most stoneware and fancier purer clays like porcelain are primary clays.

The other kind of clays that you might find are called secondary clays. Secondary clays were moved by erosion and water from one place to another. These clays may have gotten deposited by a river or stream flowing. You will often find secondary clays in places where water carries soil. Since the clay particles are heavy they will often settle and accumulate. Secondary clay can be on the banks of creeks and rivers, in the bottom of seasonal creeks and lakes, as well in layered deposits in places where water used to run. In many places people harvest their clay from sedimentary deposits that used to be underwater, but are now on the sides of cliffs and hills. This clay is dry and needs to be mixed with water before it can be used. Earthenware is almost always secondary clays because in the process of moving they have mixed with other minerals.

Look for clay

Keep an eye out for road cuts and low summer stream banks where you can find secondary clay deposits -Look for stripes of red, tan or grey that don’t match the surrounding landscape.
-Clay particles are often heavier than surrounding dirt, and they are plastic so they will stick together in layers under deposits of silt, sand and dirt.
-in areas with water, clay will often have a smooth surface when wet and smear in a smooth, not granular way when scooped of cut into with a shovel.
- If clay is dry it will crumble in a chalky way, but when mixed with water will hold together. -Try making a ball of your possible clay and letting it dry. See if it stays in its shape, and becomes hard, this is also a good test for real clay.

Clay vs. Loam

What about things that feel like clay, mould like clay, but are not actually clay? Loam is a word that geologists use to describe earth that they find that is a mix of sand, dirt and some clay. Unfortunately loam is usually less than half clay and is often what people use as a basis when they are making things like bricks, it is not particularly good for making pottery or more functional vessels like bowls and plates. How can you tell if your clay is loam, and what can you do to fix it?

How to Tell if Your Clay is Good Clay

For both tests If your clay is dry you might need to add water and knead the mixture in your hands until it is wet enough to be moldable, but not so wet that it just sticks to everything.

Coil test Make a thick coil of clay, about an inch thick, and four to six inches long. Hold it by one end. If you can dangle the weight from one end without the tube of earth breaking and falling then you probably have decent clay, since only clay is sticky enough to perform like that.

Snake test Roll a snake of your possible clay about finger thick between your fingers. Wrap the snake around your finger. If it can do this without breaking (some small cracks are okay) then you might have good clay. If the clay seems to move more like jello than play-doh then you may have a lot of super fine silt in you clay that is making it less usable.

Make Bad Clay Into Better Clay

If you are going to make your clay into usable clay the first test is to see how much work that you are going to need to do.

1. Take a clear glass or plastic jar and fill it about a quarter of the way up with your clay.
2. If your clay is dry smash it into dust before you do this.
3. If your clay is sticky and wet, make sure that it is not one hard lump.
4. Fill the rest of the jar with water. Put the lid on the jar and Shake it until all of the earth is mixed in completely with the water in one big muddy slurry with no big lumps.
5. Place the jar on a flat spot and watch it for about two to three minutes. The first things that will happen is that any plant matter, light organic dirt, leaves, roots, and such will float to the top. Similarly anything that is heavier like sand and rocks will immediately settle. The silt will take a bit longer to separate and sink down with the sand.
   
   

Everything that is still floating in the center is the clay layer. This is what you will want to separate from the rest of your earth. If the layers of dirt and plant are really big then you will need to screen for all of that matter. If the layer of sand is really big then you will have to do some separating.

Separating your clay!

To fix up your clay you are now going to need to separate out those three layers, the plant/organic layer, the clay layer, and the sand and silt layer. Some tools that will make this process easier will be:

• A garden hose or access to water
• At least two large buckets
• A fine screen, with mesh in it not too much bigger than a window screen.
• A board that you can dry your clay out on
• A cloth bag or pillowcase that you don’t like.

If your clay seems really dry, or really hard then you are going to want to dry it out in the sun and pummel it with a hammer or rock until it is a pile of dust. If your clay is sticky and mud like you can either dry it out and repeat like above, or you can just use it straight and consign yourself to more time spent stirring it to a slurry.
Put all of your ground clay or mud into one of the big buckets. Ideally, it should not fill more than one half of the bucket. Fill the bucket the rest of the way with water and stir well until everything is mixed smoothly. Let the mixture sit for a least a couple of hours so that everything can re-hydrate to the same level.

Pour your clay water slurry from one bucket into the other bucket through the screen. This is going to separate out lots of the small rocks, big pieces of sand, and much of the plant matter that might be contaminating your clay.

Add more water, and mix the strained slurry again. Let this sit overnight

Your bucket should now have a couple of definite layers in it. On the top there may be any plant matter that did not make it out on the screen. You can simply skim all of this off. There should then be a layer of clear water. Under that just like in your jar you will see a thick cloudy layer. This is your clay. Underneath there should be a layer that feels like silt and sand. It is.

Pour all of the clear water and the clay layer back into your first bucket without pouring in the silt and sand.

Now you have a bucket of just clay and water! Pour the whole mess into your pillowcase and let the water finish dripping out! Turn out the whole mess of clay onto a board and let it sit for about a day or so until it is dry enough that you can start playing with it!

Fire your Clay Traditional Style

When you fire your clay the first thing to remember is that you want to go slow! Heating up your pot too quickly is likely to make your pot crack and explode.

1. Make a big fire in a barbecue or a fire pit
2. Slowly warm your pot or pots up around the fire, turning them every few minutes so that all sides get evenly heated
3. As the pots warm up move them closer and closer to the fire until they are too hot to touch, then move them using tongs. This whole process of pre warming your pots should take at least an hour.
4. Open the fire up so that it is spread out with an open space in the middle
5. Put your pots in the open space and let them hang out there for a few minutes as they continue heating.
6. Slowly move the fire back together around the pots
7. After they have been successfully sitting in the fire for ten minutes or so begin moving adding more wood, building the fire up around the pots
8. Make the fire large and hot, keep it burning for at least an hour. At this point some people add charcoal to make a hotter fire with lots of coals. Other people use dried cow patties for a similar effect.
9. Let the fire cool naturally and only go to dig out your pots when the fire is cold to the touch.