How to Choose the Right Pottery Clay

For many beginning the journey of pottery making, sometimes it’s a bit hard for those that are beginning to choose the pottery clay body that works for them, but here’s the thing, knowing about the right pottery clay to use, and choosing the right based on set of factors that you should know about and various parts that you definitely should consider. This post will discuss how you can choose the correct pottery clay for yourself, and what types of factors go into it.

Table of Contents

The Factors

There are a few factors that you should know about, and we will go into detail about how you choose the one that you need later on. But, here is a list of the six different factors that you should know about, and the criteria to choose the clay body.

What you’re making, whether you’re hand building, sculpting, casting, or using the wheel
The surface texture you’re going for
The product usage that you’ll be utilizing
The firing temperature and the type of clay you’re firing
The size and the type of work you’re creating
The color effect of the glaze you use

These six factors are essentially what you need to keep in mind when you’re making some form of pottery, and we’ll discuss every single one of these factors in this post, and what works best for what.

Type of Pottery

There are different types of pottery that you will need to keep in mind when you’re doing this. Let’s take for example those who throw clay. For some, it may be best to use one type, but if you use it with hand-building clay, it will end up creating a lot of problems. Some factors go into this, and often, if you want to use multiple bodies, you should check to make sure they’re fit for the type of pottery work that you do.

So, what are the requirements of a hand-building clay body? Well, let’s discuss them. There are only two, and they are:

The strength
The plasticity

In terms of strength, this means how long the clay can keep the frame while it’s being made without having any sort of sagging, cracking, or overall just breaking down. Now, if you take say throwing clay, and try it with hand building, you’ll begin to notice that it actually can be a disaster because it just keeps on falling.

Now, another huge thing that you need to look at is the grog. With grog, you want to go high, and that’s because of the following:

It will hold the form
It’s better for larger and flatter objects, so if you’re making something big, you need a lot of grog
Having a high amount of this allows for better air drying time and a reduction of cracking.

So, if you’re going hand-building, you want to make sure you have the strength within this.

In terms of plasticity, this means workability. For example, you need to be able to make different things with hand building, including:

Shapes
Angles that could be sharp
Coiling
Slabs

These all take some form of plasticity, and with more plasticity, you’ll have a better time making a thing, so you definitely should make sure that can be done.

Another thing you should look into is weight. Hand-build forms are large, and often, if you want to make your life easier, you should hand-build a few of these things. how is that done? Well, it actually can be done if you factor in a bit of the kiln burning. For example, try the following:

Use pearlite with your materials
Add in some different types of kindling, and from there, see if it’ll burn better

Working with this to reduce the weight, tends to make your life much easier, and if you have a more organic burning area, it will help create a better firing schedule. You should experiment though, and see what hand-building clay works for you.

Now, for throwing clay, it’s a little bit different. We have a couple of other factors that we want to keep in mind, although they may be similar in some ways. They are:

Plasticity
Strength
Water absorption
Aging effects

Now, if you have these four factors, it will make a huge difference. You may want to look into different types of characteristics that can be put here. We’ll go into more detail on this.

Now, for plasticity, you need this, because if you’re going to be working at the wheel, it involves a lot of pliabilities. For example, you need to for the following:

Creating shapes when squeezed
Being able to turn these
Being able to pull the piece of pottery
Being able to push this around
Creating different types of shapes and sizes

Plasticity is probably the most important factor that goes into this. clay or porcelain balls are typically very plastic, so they’re good for throwing. But, as a general rule, the more plastic your clay is, the more it’ll shrink in a sense, and it has a great chance of warping when drying, so watch out for that.

For strength, you need to have a throwing clay that’s got enough to stand in an upright fashion when you’re making tall forms. You need some sand or grog in this, but in a sense, not nearly as much as hand-built clay may need.

Now, if you use grog or sand, you need to do the following with it:

It needs to be finer
It needs to not be too coarse to hurt the hands

You need some amount of grog to make stuff stand up, but the problem is, if you use a hand-building clay body, you’ll notice It’s very hard to move on the wheel, and lo and behold, it’ll hurt your hands. You should make sure it contains 9 percent max on the adhesives of the particles and not much more than that.

Now water absorption, it’s a big part of this. that’s because the longer you work with a lump of clay, the softer it’ll become when you’ve got water mixing in with it, and it’s got an increased chance of collapsing, and this also plays a huge part in limiting the size of your work. The water absorption rate is another huge factor. As a general rule, you should think of the following:

If the clay is plastic, it’ll absorb way less water than those with coarse materials
They’ll tend to be less stiff, but it also makes it harder and tiring to do this without hurting your joints
A good clay is one that’s balanced in these three factors especially

When it comes to throwing clay, watching how much water gets absorbed into this is a huge thing, especially if you’re looking to understand how to throw pottery clay well, and if you want to make a piece that’s just the right size, and one that’ll work for you.

Now, with those three factors there, let’s talk about number four, which is the effects of aging. Aging is a good thing when it comes to clay bodies, and if you’re going to be throwing it, it’s a very helpful thing, since it leads to better clay workability. To do this, you have to put it out in the open air for a couple of days after you mix it, and before you cover it. This allows for small microscopic organisms to go into the clay, and from there get bigger.

So why do you want this? Well, it’s because of the following:

These little creatures create organic polymers
This adds to more plasticity in the clay with none of the drawbacks that might come from fine particle clay
The only drawback is that this can stink in many cases
If you do this, you should note that it’s got nepheline syenite in it, so you shouldn’t store it for more than three months due to particle ionization

Aging can help, and you should make sure that you’ve got a clay body that will work with this, and not go against the effects of aging that would be there, and in turn, you’ll be able to create the best and most workable clay pieces that you can as a result of this.

Now that you know that there are factors that affect each of these different types, let’s talk about the other factors that go into actually choosing the correct pottery clay.

Size and form

If you’re going to be making something bigger, you need a strong clay body, as mentioned before. If you don’t have this, ultimately the following will end up happening.

Shrinkage
Accuracy issues

Clay shrinkage happens in drying and firing. However, it does shrink at different rates, from as little as 4% to as much as 15. That means you need to account for the size, and the form of this, and you need to account for the temperature shrinkage that can happen.

For some of these the higher the firing, the more shrinkage you get. In some tests, if you fire it at cone 6, it’ll shrink about 11% or so. If you do a bisque fire, it also might shrink as well, about a percent or two. It shrinks in drying and during both normal and bisque firing.

That’s why it’s important to do test batches when it comes to this stuff. That way, you’ll know for certain how bad the shrinkage will be.

You need to account for this, since if it’s got more water in it, the more shrinkage you’ll get. As well, if it has a lot of water, it may also reduce in terms of strength too. You need something that has a certain shrinkage rate, but also something malleable too. When choosing a clay, this is a very important point, and it’s something that many tend to forget, but it’s a huge part of it, and if you want good results with clay making, this is ultimately the thing to do.

You should also keep in mind that if it does end up getting small when throwing or building, it’ll get even smaller when firing. That means you’ll want to ensure that you keep all of your clay bodies mixed fittingly, and also make sure that if you need to test fire, you’ve got the right kind of clay for this, and test a batch before you do.

What you’re making

You need to look at the machinery that you’re using as well. this isn’t just the throwing wheel, it’s much more. Using these types of machines will help you improve the state of your clay, but, these also affect the type of clay you’re going to use.

If it says it needs to be mixed with a clay mixer, do this. You should look at the strength, the plasticity, and also the water absorption and weight if you’re wondering whether to use clay, but this also applies to how you work with it. Knowing how to accurately and adequately use this with your equipment is a huge part.

Some of the clay processors you may be using are:

Pugmills
Clay mixers
Tools to wedge
Shaping tools such as the wheel, slab roller, and an extruder
The kiln that you’re using, how long you’ll be able to use the kiln, and accessibility

These are actual factors that determine the clay that you should get, and the tools of the trade do have a large part in how you’re going to be utilizing these in the future as well.

Firing temperature

Clay bodies have a huge variance in terms of the temperature that you fire it as well. clay bodies, along with glazes, have different maturation temperatures, and this affects the type of clay body you’ll need to use to fire.

When you fire clay, sometimes the clay that you use can affect different things. For example, the following can happen:

It may shrink
It may affect the state of the glaze
It may affect the porous nature of it

For some clays, if you’re going to single fire, you have to use a certain type. Earthenware, for example, is a good one if you’re single-firing. But, porcelain can’t work in that way and instead needs a bisque. That means earthenware pieces can be made slightly smaller if you’re single-firing, but it also affects the types of glazes that you can use with this.

When you’re looking to think about what type of pottery you’re going to make, you also need to think about the clay, and how it might affect the kiln and such as well. It does play a huge part, and you’d be amazed at the difference this may make.

There are three different firing temperatures, and while yes, all of them are pretty hot, they still make a difference. They are:

Low fire: fired at a lower temperature, but good if you’re looking to bisque, or maintain a design on your piece
Mid-range: used to help dry the piece out, and ultimately can be used as the main firing temperature for pieces without a certain glaze of stain on it
High fire: used for a high-temperature piece, and if the clay matures at a high rate, you should be using this. Typically, not used for a long time with decorative pieces, and when you single fire, you only use this for about an hour or so

If you’re going to be firing, you should know your different types of clay, so that you can use these effectively.

Glaze effects

Clay glazes can also affect the type of clay as well. clay comes in three different colors, and they are:

White
Off-white
Terracotta

This can affect the glazes that you choose, and the finished ware as well. You may look at the clay body, and it says that it requires only certain types of glazes or some of the glazes should only be used on some types of glazes.

Ideally, if you’re going to be working with a certain type of clay, you should do a test tile first before you continue. That way, you can look to see what you get from this. to do this, you do the following:

Shape some tiles, typically with slab pottery, but you can use throwing clay as well
Use some of the glazes, especially translucent ones
Fire them, and see the difference

You can also do this with different types of clays as well, such as may be trying this with earthenware clay fires, and then porcelain, before you commit to this. As of note as well, these darker clay colors can be quite messy, and the same thing goes with a dark glaze. They’re much harder to clean off the floor, hands, and even tools, and they can stain clothing. If you’re going to be working with this type of clay, you should make sure you take the right cleanliness actions before you begin, and if you’re going to be working with multiple clays, you need a recycle bin for every single type, along with a wedging board, and don’t share the dark and light clay so that it doesn’t contaminate the place.

When it comes to clays, the glazes do matter, and you’ll be able to create different types of pieces that you’ll be able to enjoy no matter what, and you’ll be able to make the right kind of clay body for yourself too.

Buy or make your own

Finally, you can choose to buy your clay bodies or make your own. Some people like to make their own, and that’s because of the following:

If you’ve got local clay around, it can create a cool piece
It offers a sort of uniqueness
Can cost less money
It might way less
You can use custom clay bodies

However, it often may lead to different results. If you need a certain amount of sand or grog to it, it may be best if you choose the bought clay.

With bought clay, you get different advantages as well:

It’s convenient
Easier on you
You don’t have to wedge the clay
It often can be easier to figure out what types of glazes you use
Less experimental, so it might be more user-friendly for those beginning

You can get commercial moist clays, and if you’re not the type of person that has a lot of materials to start that would help with mixing the clay, sometimes it’s easier to buy your own. But, this often can weigh a lot more, and it does rack up after a long time. It often can be quite hard, and you might realize that it’s harder for you to get some. But, with mixing clay yourself, you don’t have to worry as much about shipping or expenses. However, whatever you do, know that they fall into those three types, and you’ll be able to adjust them as needed

For many, these commercial clays are the way to go, and if you know how to use them rightfully, you’ll be able to create some of the best and most creative pieces that you can. Using the right kind of clay is important because it affects the overall state of the work itself. You’ll be able to utilize this effectively and be able to create the best pieces possible. Know about the factors that affect choosing your clay, and get the best kind of clay that you can for this. You’ll save yourself a lot of heartaches whenever you do choose this, and you’ll be able to as well decide the various aspects of this, and be able to make the right kind of clay body not just for one piece, but for all of the clay pieces you make.