How to Choose the Right Pottery Clay for Your Project
Pottery clay comes in four primary types—earthenware, stoneware, porcelain, and slip—each with distinct qualities suited to different projects. Earthenware is affordable and easy to use but remains porous after firing. Stoneware offers excellent durability and is ideal for functional pieces like tableware. Porcelain provides a refined, vitrified finish and fires to a bright white and even translucent with certain recipes. Slip is highly plastic and smooth. Choosing the right clay depends on your firing setup, intended use, and skill level.
One of the wonderful things about pottery is the immense selection of materials that potters and ceramic artists have to choose from. Of course, for a beginner, that’s also a slightly intimidating thing – out of the hundreds or even thousands of options, how do you choose the right clay for a given project?
Fortunately, making the right selection doesn’t have to be complicated. Just as a woodworker will tell you that different woods are appropriate for different furnishings or finishes, different clays are best for each specific type of project, glaze, or firing temperature.
This month, we’re looking at the main categories of pottery clay. For each one, we’re giving some information on the types of projects that each lends itself to most effectively, as well as some details about firing temps. We’re also sharing some of the challenges each type of pottery clay can present so that you can choose a clay that fits both your project and your experience level.
What Is Pottery Clay?
Just about any clay that’s found on Earth has been used for pottery at some point; the ones that are best suited for the job have been continually worked and improved over time to become the vast range of commercially available pottery clays on the market today.
All types of clay started as rocks and shells or crystals that were gradually worn down to tiny particles. Unlike sand, where you can see and feel individual grains, the individual grains of clay are too small to be seen with the naked eye. Clay grains are usually broad and flat, which gives clay the ability to be formed and hold its shape while it’s being worked, dried, and fired. The chemical properties of the various rocks and crystals that make up a pottery clay determine its color, workability, and firing temperatures.
What Are the Main Types of Pottery Clay?
Nearly all pottery clays fall into one of four main categories, each with unique strengths and weaknesses.
Earthenware Pottery Clay
Earthenware clay is the most popular type of pottery clay; hence, its other name is common clay. It most closely resembles the kinds of clay we find at the surface in nature and is typically high in impurities. Earthenware clays are available in a wide range of colors, including red, orange, terracotta, brown, white, and pale grey.
Earthenware clays are the easiest to work with and least expensive due to the shorter firing cycles. This reduces energy costs. They fire at the lowest temperatures of any clay, between Cone 6 (1828° F) and Cone 03 (1987° F), meaning that even small entry-level kilns can successfully fire earthenware pieces. In exchange for this ease of workability and low firing temperature, earthenware clays are a bit less durable.
These clays are good for general-purpose pottery projects, including sculpting, wheel-throwing, hand-forming, and other techniques. Flowerpots, sculptures, and even homewares can be made from earthenware clays, but it’s important to pay attention to the clay’s porosity when choosing it for something like dinnerware for daily use.
Earthenware clays don’t undergo vitrification (reaching a glass-like state) when they’re fired, so they remain porous even after their trip through the kiln. If you’re using earthenware clay to make a piece that will be used to hold food or drink, make sure to choose a glaze that will provide an adequate barrier between the clay and the food/drink.
Stoneware Pottery Clay
Much denser than earthenware clays, stoneware clays offer increased strength and durability over their less-dense cousins. In fact, the name “stoneware” comes from the fact that these clays, when fired, produce a product that closely resembles solid stone. It’s available in colors ranging from white to rich brown and is typically very smooth and fine-grained.
Stoneware clays are also easy to work with but will usually cost a little more to fire than earthenware clays. Stoneware fires at higher temperatures, from Cone 5 (1186° F) to Cone 10 (2345° F), so some smaller kilns may not be able to get hot enough to fully fire stoneware pieces. Once fired, however, stoneware is the most durable pottery, with incredibly high resilience and toughness.
Stoneware is an excellent choice for making practical, everyday items like tableware. When fired, stoneware clay is considerably less porous than earthenware and can even produce a vitrified surface if fired hot enough.
Stoneware clays are very workable and are typically used in hand-forming and wheel pottery.
Porcelain Pottery Clay
Porcelain clays can be turned into exquisite pieces with fine details and a stunning smooth finish, but they do come with some additional challenges.
Porcelain undergoes vitrification during its hotter firings, leaving the finished piece with a glass-like surface. Thanks to the high amount of kaolinite contained within, porcelain is almost exclusively found in white and off-white colors.
Porcelain clays are both more expensive and considerably harder to work than earthenware or stoneware. Porcelain clay is more elastic than the other types but not as plastic – meaning it’s harder to form into a desired shape and is more likely to collapse and lose its form than other, heartier clays. As such, beginners should get well-versed in slinging earthenware and stoneware clays before venturing into the world of porcelains.
If you’re planning to fire porcelain, you’ll need a kiln that can fire to at least Cone 10 (2345° F) or higher. Bone china clay, a type of porcelain, is commonly fired up to Cone 36 (3272° F) to obtain its rich glassy finish.
The difficulty in working porcelain means that it’s frequently used in slip molding instead of free-form techniques like hand-forming or wheel throwing. Experienced potters can produce good results on the wheel, but it takes practice to deliver quality work. Porcelain is commonly used in fine tableware but is also found in several utility roles – in toilets and other plumbing fixtures, as an insulator in electronics, and in other cases where a strong and reliable glassy finish is required.
Ball Clay and Liquid Slip Pottery Clay
Slip and ball clay are essential components in ceramic and pottery production. Slip is a liquid mixture of clay and water, often used to cast shapes in molds, join pieces of clay together, or decorate surfaces. It can also serve as a base coat in various glazing techniques. Ball clay, on the other hand, is a fine-grained, highly plastic clay that enhances the workability and strength of ceramic bodies. It’s commonly added to other clays to improve their plasticity and binding properties. Both materials play crucial roles in shaping and refining ceramic ware before it’s fired in the kiln.
Still Need Help Choosing a Pottery Clay? Call the Experts!
Call us today at 888-838-3625 or email info@clay-king.com for guidance and assistance on selecting the right kind of pottery clay for your next project.
Should you be slinging earthenware, stoneware, porcelain, or ball? We can help you decide. We carry clays of all types and colors from producers like Mammoth Clay Company, Laguna, Amaco, and Kentucky Mudworks. We’ll be glad to talk you through your options and help you zero in on the products that will take your pottery to the next level.
Call us today to get started on your clay-shopping journey: 888-838-3625
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