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Things to Consider Before Buying Clay for Pottery

What is clay?

Clay is fine-grained earth that can be shaped when wet. It contains sand, minerals, tiny rocks and other natural soil components in different concentrations. Clay comes in a variety of textures and colors depending on their particle size and composition. Clays that have high concentrations of iron oxide tend to have a rusty, red or orange appearance while those with no iron at all look gray or even white, which is the case with porcelain clay.

Clay is used in a variety of fields and has endless applications. Industrial clay, for example, is commonly used in the building industry to make bricks, walls and pipes while it can also be used for 3D modeling design products. In this article, however, we’ll only cover clay used for pottery making. 

There are different kinds of pottery clay and they all have their own properties that make them more or less suitable than others for specific projects. Here are the properties you need to keep in mind when buying pottery clay:
  • Shrinkage: Clay shrinks when it dries, which means that your pieces will be slightly smaller once they go through the firing process. Shrinkage percentages go anywhere from 5% to 15% depending on the kind of clay.
  • Absorption: The absorption percentage refers to the amount of water a fired piece absorbs in relation to its own weight. It goes anywhere from 0 to 15%.
  • Firing temperature or temperature range: The temperature in which a piece needs to be fired at to reach maturity. These temperatures and the time the pieces need to be fired vary depending on both the type of clay and the size or thickness of the piece.
  • Plasticity: This refers to how easy it is to pull, shape or manipulate clay when wet. The higher the plasticity, the more flexible and easy-to-work the clay is.
  • Grog: Grog is clay that has previously been fired and then crushed. It comes in different particle sizes and it’s usually added to clay to give it a different texture and reduce the shrinkage of the piece. You can buy clay and grog separately and mix them together yourself, or buy clay that already has grog in it.

 

Types of clay for pottery

 

There are 3 main types of clay for pottery: stoneware, earthenware and porcelain clay. They are all used for different purposes and have different characteristics and properties.

Stoneware clay

Stoneware clay is the most versatile and easiest to work with. If you are a beginner who's trying pottery making at home for the first time, we recommend you to get stoneware clay. It comes in a variety of colors from white to dark brown. Once fired, pottery made out of stoneware clay is very durable, strong and non-porous, which means it will be capable of holding liquid without having to glaze it. 

It has a firing temperature range of 1100 °C (2000 °F) to 1300 °C (2370 °F) and it can be fired more than once.

Stoneware clay is ideal for making objects of any size, from small plates to big vases. You can use it on a pottery wheel or to make items using handbuilding techniques.

Earthenware clay

Earthenware clay tends to be thicker and heavier, but weaker than stoneware. The most common kind is Terracotta, it has a rich red color and is commonly used to make tiles and flower pots.

Earthenware clay is known to be a low-fire clay as it only needs to be fired at approximately 1100 °C (2000 °F). Items made out of this kind of clay are naturally porous, which means that they are not capable of holding any liquids; if you want them to be permeable, you’d need to glaze them and fire them a second time. This extra step requires extra time and materials, which might not be ideal for beginners.

Porcelain clay

Porcelain clay is very soft and more flexible than the other kinds of clay but it's quite difficult to shape. It requires a lot of water that needs to be strategically added to the mix while shaping it; if you don’t add enough water it quickly dries out and if you add too much water it can easily lose its shape and collapse. Learning how to work with porcelain clay takes time and a lot of practice, so it might not be the best option for those who want to try pottery making at home for the very first time.

Porcelain clay has the highest firing temperatures of the list, which varies between 1,200 °C (2,200 °F) to 1,400 °C (2,550 °F). Such high temperatures are quite difficult to achieve without a kiln

Porcelain pottery looks beautiful. However, you might want to wait until you’re more experienced to give it a try.

What’s the best clay for pottery wheels? Well, all stoneware, earthenware and porcelain clays work well on pottery wheels. As we explained before, some are easier to shape than others, but they are all suitable for wheel throwing.

How to make pottery clay

Making pottery clay at home is quite an easy process. There are a few techniques you can use to process clay, of which the easiest and most popular technique is known as “the wet method”. 

Making pottery clay from dirt or soil using the wet method consists of mixing soil and water in a big container and letting the mix sit for a few minutes to let gravity pull down the bigger rocks and sand to the bottom of the container, leaving just water mixed with clay on top. This water is then filtered using a fine cloth, leaving nothing but wet, smooth clay that can be used immediately or saved for later.

 

Where to buy clay for pottery

You can buy clay for pottery in different places depending on the quantity and type of clay you need. 

If you are looking to buy small quantities for making pottery at home just as a hobby, you can get them in most art supply stores or online suppliers.

If you are looking to buy more specific types of pottery clay, or if you want to buy over 20 lbs of it, we advise you to get it directly from a local supplier as it’s going to be cheaper than getting it online. Also, by going to a local supplier, you will get all the help you might need to buy the right kind of clay for your projects. Most suppliers make their very own clay so you will be supporting a local business too!

 

How to dry pottery clay

To dry pottery clay, you’ll need a kiln

A kiln is an oven used to fire clay and melt glass

There are gas kilns and electric kilns.

Gas kilns work with natural gas or propane. They give ceramics a darker color and a rustic, aged look. Electric kilns are easier to install and operate than gas kilns. They work with heating elements that are basically pieces of wire designed to resist the passage of electricity, similar to most heating appliances. 

Electric kilns are definitely the best option for both beginners and professionals. They come in a variety of sizes and prices that fit anyones’ needs. 

At Soul Ceramics, we are experts on electric kilns. We know everything about them! If you want to take a look at our catalogue, you can check our electric kilns page. If you want more information about them, here is an entire guide that will tell you everything you need to know about kilns and firing pottery. 

Can you put pottery clay in the oven?

No, you cannot fire pottery clay in a regular kitchen oven simply because it doesn’t reach the high temperatures clay needs to be fired to (at least 1100 °C or 2000 °F).

If you don't want to buy a kiln, you can always pit fire clay at home, but that’s complicated to set up and achieving the specific temperature needed for specific kinds of clay is even more difficult. If it’s too hot your clay will melt and if it’s not hot enough it won’t dry properly. So, if you want to fire pottery the right way, you’ll definitely need to buy a kiln.

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