Deciding on the type of clay you're going to use depends on what you seek to do with the pottery you make.
It can be difficult to decide on a clay, though, especially because there are a lot of different factors that determine the end results. It's important that you know what kind of materials you're working with if you're going to spend time on a project.
We've created a basic guide to the different types of clay that you're likely to use in any entry-level project.
A Guide to Different Types of Clay
There are three general categories that are used when referring to clay bodies. "Clay bodies" are essentially the particular compositions of the materials used for clay.
The general categories are earthenware, stoneware, and porcelain. Each of these has different characteristics that affect the workability, end result, and fragility of the product. There's also an additional "pure" clay called kaolin.
Porcelain is very dense and strong and can prove to be an exceptional material to use if you plan on creating pottery for any functional use. By this, we mean things like bowls and cups, because porcelain is able to hold heat or cold for longer periods of time than its counterparts.
It is not very porous, and this is why it tends to hold its temperature so well.
Some people have the impression that porcelain is difficult to manage while spinning, but the newer formations of clay have streamlined this and the material is quite malleable.
It usually comes in a finely grained white body, the color coming from its high kaolin levels. Once fired, the clay becomes exceptionally strong and durable, making it a great choice for those creations that will do more than sit on a shelf.
Because it is vitrified, it won't get contaminated by any other elements that you may put into the body. Porcelain holds color, it is cheap, and it's usually available.
Porcelains usually need to be fired at temperatures 2,190 to 2,550 degrees Fahrenheit.
Porcelain is known to have been developed in China, reaching its fully-evolved state somewhere around two thousand years ago. The material and practice of using porcelain spread slowly into Eastern Europe and East Asian countries.
The precision and craft that is possible when using porcelain are confirmed by an unprecedented amount of beautiful art created with it.
Stoneware is generally known for its need to be fired at a high temperature. It is also non-porous, and it fires into a pretty durable material. Stoneware should be fired at a temperature around 2,010 degrees Fahrenheit, up to just under 2,400 degrees.
Its natural colors can be various. There is stoneware that can be extremely light gray, tan, dark gray and brown. The material is typically not used for dinner plates or the like. Instead, it is used for large jugs and crocks.
Stoneware is often seen as a close relative of porcelain, although it can't truly be categorized as such because it has a few primary differences. Stoneware is known to be more opaque than porcelain, meaning that it is less able to allow light and other kinds of waves through its walls.
Kaolin is a Chinese substance that is known to be extremely pure, containing little-to-no impurities.
The substance gets its name from a town that is extremely close to where it is found. Kaolin is a difficult substance to work with at times, though, because it is not plastic enough to be easily molded in the hand.
It will break if it's treated too roughly, and it takes a skilled potter to work with it in just the right way. Once fired, the substance will become translucent and the surface of the pottery will become very shiny and smooth.
For this reason, potters never need to use a glaze with materials made of kaolin.
What Makes Clay "Good?"
All of the forms of clay listed above come in a variety of qualities. Some forms of earthenware might be better than stoneware, and some forms of porcelain might be better than earthenware. What matters is the quality of the clay at hand.
But what makes some clay high-quality and other clay low-quality? A number of things, but the most important is the presence of impurities. These impurities are typically sand. Sand deeply disturbs the quality of the clay at hand, making it brittle, hard to mold, and week.
If you're working with clay that is brittle, hard to shape, and easily broken, there are a few things you can do. To test the clay, roll it up into the shape of a pencil. Try and wrap that piece of clay around your finger.
If the clay wraps around your finger without any cracks or breaks, it might be decent clay. If the clay does break, however, it's likely that it's got a lot of sand in it.
There's a decent way to remove sand from clay that you already have, so don't throw your supplies out!
Take the impure clay that you have, fill up a bucket of water, and place the clay into that bucket. Put your hands in and break up the clay so that there are no noticeable chunks and the water has blended with the material evenly. Let that clay sit in the bucket for two or three days.
You'll find that the materials in the bucket have separated into three layers. The top layer is going to be sitting water, which you can just pour out. The second layer is your clay, and the third layer is all of the sediment and sand that was present in it before.
Separate the clay, and you should find that the material is much easier to work with after being purified.
Interested in Learning More?
You're likely creating pottery that will be in contact with plants or gardens. If you're making moves to create a beautiful, healthy garden, there are some things that you need to know.
If you're interested in learning the insider secrets of gardening the right way, we've got the information you need.