The Wonderful World of Clay
(Sample Article)
Intro
Stiff. Sticky. Sloppy.
Moldable. Muddy. Messy.
And most importantly, fun.
How could slabs of such densely packed dirt become your grandmother’s fine china or your latest living room accent piece?
Welcome to the wonderful world of clay.
Basics
To begin, it’s not exactly dirt.
“Clay is a mix of minerals and organics and it’s found in the ground, it’s not exactly like dirt because it’s a specific chemical makeup that makes it specific to clay. A lot of that has to do with the way its minerals interact with water. The water content in the clay minerals makes that stickiness and it holds together and that’s really what you want,” says Hood College art and archeology professor Jenna Gianni.
What makes clay the magical moldable material that it is? Just add water.
“The water, plus the natural soils and minerals is what makes clay so special, because when its wet it allows us to make essentially anything we want,” says visiting Hood College art and archeology professor Taylor Pasquale.
The clay becomes incredibly strong once it’s fired in a big oven called a kiln.
“It’s virtually indestructible once it's dry, unless you crush it up into a fine powder it’s not going anywhere. That’s why when we study civilization from hundreds and hundreds of years ago, we’re looking at this stuff because it lasts and it tells a story,” Pasquale says.
And you can’t find it just anywhere either.
“If you try to dig up dirt in the backyard and you try to make something with it there’s no control there,” says Gianni.
Gianni further explains that all around the world there are different types of sedimentary material mixed and tightly compact with a special consistency of minerals, natural soils and chemicals that create clay. These tightly compact clay formations are called clay deposits. The durability
and strength of that clay depends on where those clay deposits are formed. determine what type of clay you are working with.
So, if you flood your lawn like a hurricane hoping to make clay, don’t expect anything but a grimy backyard and a high-water bill.
Types of Clay
Clay — seems simple, but what is it really?
There are so many different types. Some of it is brown like the soil in a garden, or rusty red like autumn leaves, or even bright white like a fresh coat of snow.
All of which have names: earthenware, stoneware, and porcelain.
“They’re both very specific in their names and abilities, but extremely interchangeable in their use,” Pasquale says.
The two major forms are called primary and secondary.
“Darker clay bodies are considered secondary clay and porcelain is considered a primary clay. Secondary clays were formed, but through erosion, they got washed away to different areas and they pick up stuff and these are the stoneware and the earthenware,” Pasquale says.
They’re obviously interconnected, but if you don’t understand them, the terminology can become a bit muddy.
Earthenware
“Earthenware clay is typically fired at a lower temperature because the makeup of the clay would not last in a kiln with temperatures going above 2,010°F,” says Cassidy Stoner, owner of Frederick Clay Studio in downtown Frederick, Maryland.
It’s also fairly inexpensive. On average it costs $17 for 50 pounds of earthenware clay.
The most common type of earthenware ceramic piece is terracotta. Usually, you’ll see these in the home and garden section of your local hardware stores like Home Depot and Lowe’s. They’re burnt red and orange in color, and you’ve most likely seen them seated on a porch or window-sill holding petunias, pansies, or other pretty flowers.
“They are not quite as strong, but the reason they have a lot of red in them is because they have a lot of iron content in them and impurities that make them that color,” Stoner says.
Stoneware
In terms of strength, the stoneware is one step above the earthenware clay.
“Now, the stoneware is a bit of a stronger clay than the earthenware, but it’s not as strong as the porcelain. It’s a happy medium between the two really,” Stoner says.
Happy medium indeed. Your stylistic preference will determine the type of glaze you use, and the temperature your piece is fired at. Stoneware can be fired in a kiln between 2150-2260°F for a mid-fire, or 2200-2336°F for a high firing. And it has less impurities than the earthenware, giving it a muted gray color.
You can find stoneware pieces in most stores like Walmart and Target — and especially stores like Home Goods and Crate & Barrel, who sell a mass amount of kitchenware products that are made out of stoneware.
The stoneware is a little more expensive than the earthenware. The average price of standard stoneware clay is $30.
“Community studios like ours use a lot of the stoneware clay, because it's stronger than an earthenware clay, but it’s not as expensive as a porcelain clay,” Stoner says.
Porcelain
Finally, the most expensive and the strongest clay. The porcelain.
“The porcelain clay body has formed in the earth for thousands and thousands of years and is usually dug up right where it was formed. So, it’s nice and pure and it doesn’t collect any dirt,” says Stoner.
The porcelain is stiff. It takes time and patience to work with it, but the finished piece is the most durable of the three clay bodies. It takes a lot of heat for the glaze finish to properly melt onto porcelain clay, which is why it is fired at 3272°F.
While porcelain may be harder to break, your bank just might. On average standard porcelain clay can cost between $50 - $60.
It’s expensive, it's flashy, it’s your grandma’s fine china.
Takeaway
If you’re thinking about buying your own clay, or signing up for a community ceramics class, remember: the clay you use is mostly a stylistic choice.
“I like to use porcelain for sculptures, but I also sell mugs and cups and bowls and for that I use stoneware. There really isn’t one type of clay that’s more popular than the other because each one is still useful depending on your project of piece. It’s more about the vision you have for your project, so if it makes sense to you, then it’s a good piece,” Gianni says.