What Clay To Work With?

Clay is one of the most versatile and widely used materials in pottery and sculpture. The type of clay an artist chooses to work with can have a significant impact on the final outcome of their creations. There are several major categories that clay can be divided into based on properties like firing temperature, plasticity, color, and texture.

The four most common types of clay are earthenware, stoneware, porcelain, and terra cotta. Each has their own unique characteristics that make them suitable for different applications and artistic goals. Some clays are better for handbuilding and sculpting, while others excel at throwing on the pottery wheel. Understanding the strengths and limitations of various clays will help artists select the right material for their needs.

This guide provides an overview of the major clay categories, their key attributes, and what types of projects they are best suited for. With the right clay body, artists can bring their creative visions to life in ceramics.

Clay Types

There are several main types of clay used in pottery and ceramics. Knowing the differences between these clays can help you determine which is best for your project.

Earthenware is a porous, opaque clay that is fired at lower temperatures, usually between 1700°F-2100°F. It comes in a variety of colors including red, brown, buff, and white. Earthenware has a coarse texture and absorbs water easily, making it ideal for items like flower pots and decorative pieces. It is one of the most commonly worked clays.

Stoneware is less porous than earthenware and non-absorbent when fired between 2200°F-2400°F. It has excellent strength and durability. Stoneware clays are typically grey, brown, or reddish-brown. They are commonly used for kitchenware, ovenware, and other functional items.

Porcelain is a highly refined, white clay that becomes translucent when fired at very high temperatures of 2300°F-2600°F. It has very low porosity, providing an impermeable, glass-like surface. Porcelain is smooth, strong, and delicate. It is ideal for items like tableware, figurines, and high-end decorative objects.

Terra cotta is an unglazed, porous earthenware clay that has a distinct orange-red color. It is naturally semi-permeable and has a coarse texture. Terra cotta clays are typically low-fired between 1700°F-2100°F and are commonly used for flower pots, garden ornaments, architectural decoration, and artistic sculptures.

Earthenware Clay

Earthenware clay is one of the most common types of clay used for pottery. It’s a porous, opaque clay that is fired at lower temperatures than other clays, usually between 1700-2100°F. Earthenware has some key properties and uses:

Properties:

• Porous and absorbent – earthenware can absorb water
• Opaque appearance
• Fired at lower temperatures around 1700-2100°F
• Prone to chipping and cracking
• Heavier than other clays

Uses:

• Pottery such as vases, pots, cups, plates
• Decorative and functional tile
• Bakeware and oven-proof dishes
• Flower pots and planters

Earthenware’s absorbency and lower firing temperature make it a versatile, beginner-friendly clay for a wide range of pottery uses. It’s an accessible and affordable option for crafters and artists.

Stoneware Clay

Stoneware clay is dense, strong, and nonabsorbent. It has high firing temperatures, typically between 2200°F and 2400°F. This higher temperature allows the clay to become vitrified, making it a durable material that is fully waterproof and nonporous. Stoneware maintains its shape well during throwing and is great for both functional ware and sculptural pieces that require more structural strength.

The main properties and characteristics of stoneware clay include:

• Dense and strong – It has very low porosity so it does not absorb water.
• Vitreous and nonpermeable – The high firing makes it completely waterproof.
• Withstands thermal shock – It resists cracking from sudden temperature changes.
• Wide firing range – It can be fired between 2200°F and 2400°F.
• Low shrinkage – It has about 10-15% shrinkage from wet to fired state.
• Good plasticity – It is smooth and durable for throwing on the wheel.
• Available in various colors – Natural colors and stains can create various looks.

Stoneware has many uses including:

• Dinnerware – Plates, bowls, mugs, and more.
• Kitchenware – Jars, pitchers, teapots, and other items.
• Outdoor pieces – Planters, yard art, and architectural elements.
• Sculptures – From abstract to realistic figural works.
• Tiles – For floors, walls, countertops, and backsplashes.

Porcelain Clay

Porcelain clay is known for its white color and strength when fired. It is made from kaolin clay that has been fired at very high temperatures between 2,200°F and 2,460°F. This makes porcelain harder and less porous than other clays. Porcelain can be molded very thinly and maintain its shape, resulting in delicate, translucent pieces.

Some key properties of porcelain clay are:

• Very white in color, even after firing
• Low absorption rate, resulting in a non-porous surface
• Highly resistant to staining and water absorption
• Very strong and durable after firing at high temperatures
• Can be molded thinly while maintaining structural integrity

Porcelain is ideal for creating tableware like plates, cups, vases, figurines, and other fine pieces where strength and whiteness are desirable. The translucency of thin porcelain makes it perfect for lighting fixtures as well. Artists also use porcelain for sculpture and decorative wares. When mixed with other clays, it can be used to create unique hybrid ceramics.

Terra Cotta Clay

Terra cotta clay is made from sedimentary clay that has been fired at a high temperature, giving it a distinctive reddish-orange color. It is a highly porous type of earthenware clay. Some key properties and uses of terra cotta clay include:

• It has a coarse texture that allows air and moisture to pass through it easily.
• It is porous and absorbent, which makes it suitable for handbuilding techniques like coil and slab building. The porosity allows water to evaporate while the clay is drying.
• When fired, it becomes harder and more durable while still retaining its porosity.
• It has low plasticity, meaning it is stiffer and less malleable than other clays.
• Terra cotta has excellent thermal properties and can withstand extreme temperatures. This makes it suitable for baking, grilling, and oven use.
• It is commonly used for making flower pots, vases, bricks, roof tiles, and other architectural elements. The porous quality helps protect buildings in hot, dry climates.
• Terra cotta sculptures, busts, and decor pieces are popular because they have an antique, antiqued look.

Choosing Clay

When selecting clay for a project, there are several factors to consider based on the type of piece you want to create:

Intended Use: If making functional pottery like mugs or bowls, choose a sturdy stoneware or porcelain. For sculpture or decorative pieces, choose a clay based on desired aesthetic.

Firing Temperature: Match the clay type to your available kiln. Earthenware fires at lower temperatures, stoneware at mid-range temps, porcelain at highest temps.

Color and Texture: Choose a red or brown earthenware for a rustic look. Porcelain is pure white. Stoneware comes in grey, buff, white. Terra cotta has an earthy finish.

Skill Level: Beginners may want to start with an easily workable earthenware. More advanced potters can work with delicate porcelain.

Kiln Availability: Make sure you have access to a kiln suited to the firing requirements of the clay you choose.

Project Size: Small sculpture or jewelry pieces can be made from porcelain. Larger pots and vessels require sturdier stoneware or earthenware.

Test different clays to see which you enjoy working with most. The characteristics and workability of the clay will impact the finished results.

Preparing Clay

Once you have chosen the appropriate clay for your project, some preparation is needed before you can begin sculpting or throwing on the wheel. The main techniques for preparing clay are wedging, slaking, and kneading.

Wedging involves cutting the clay block in half, standing it on its side, and pushing it in to reform the block, while squeezing out any air bubbles. This helps homogeneous the clay by blending different moisture levels, removes air pockets, and aligns the clay particles. Wedging is best done on a plaster bat or wedging table.

Slaking is mixing clay powder with water until it forms a smooth paste free of lumps and dry spots. Start by sprinkling bits of dry clay into a container of water, mixing continuously. Once thoroughly mixed, allow to sit for at least 4 hours before wedging to distribute moisture evenly.

Kneading clay by hand is essential for conditioning it to the right stiffness. Similar to wedging, kneading blends moisture and aligns particles. To knead, flatten the clay slab, fold it over itself, then press down with the palm of your hand. Rotate and repeat until the clay is uniform. Kneading helps remove air pockets as well.

Taking the time to properly prepare clay results in a consistency that is smooth, elastic, and lump-free – ideal for shaping intricate forms without tears or cracks.

Storing Clay

Proper storage is crucial for maintaining the quality and workability of clay. Here are some tips for storing clay:

Keep clay in sealed airtight plastic bags or containers. This prevents the clay from drying out. For best results, knead the clay before sealing to remove any air pockets.

Store clay in a cool, dry location away from direct sunlight. Ideal temperatures are between 60-70°F. Avoid fluctuation in temperatures as this can cause condensation.

For long term storage, consider freezing clay. This stops the aging process. Defrost frozen clay slowly in the refrigerator before using.

Place clay on boards or wax paper if storing directly on shelves. Don’t stack plastic bags directly on top of each other as this can cause clay to flatten.

Clean clay working surfaces and tools before storing clay. Bits of dried clay can contaminate fresh clay.

Label clay with type and firing temperature. This helps keep track when working with multiple types of clay.

Avoid storing clay long term, more than a year. Clay can expire over time, becoming difficult to work with.

With proper storage methods, clay can be kept workable for months. Follow these tips for storing clay based on your workspace and projects.

Conclusion

When choosing the right clay to work with, it’s important to consider the type of project you want to create and the level of skill you have. The four main types of clay each have their own properties that make them better for certain applications.

Earthenware clay is very beginner-friendly but susceptible to chipping and cracking. Stoneware clay requires higher firing temperatures but results in a very durable finished product. Porcelain clay is difficult to work with but can be fired at very high temperatures to become translucent and delicate. Terra cotta clay is natural clay that has good absorption properties to allow planting directly into finished pieces.

It’s a good idea to test out small amounts of different clays when you are new to pottery. Consider the firing temperatures you have access to as well as the characteristics you want for your finished pieces. Proper preparation, storage and handling will help any clay maintain its ideal consistency.

With some knowledge of the different clay properties and types, you’ll be able to choose the right clay for your next pottery project.