Appreciating ceramics and the pottery process
What is Pottery?
Pottery involves shaping and firing clay to create vitrified objects, typically vessels designed to hold water and food. In Western classification, pottery is generally categorized into three main types: earthenware, stoneware, and porcelain. This classification is based on characteristics such as the type of clay used, the hardness of the fired piece (biscuit), density, water absorbency, and the presence or absence of glaze.
It's interesting to note that the criteria for classifying ceramics can differ slightly between China, Japan, Korea, and Western traditions. Furthermore, the ancient craft of pottery is thought to predate the invention of the potter's wheel.
Earthenware
A low-fired ceramic ware that is not fully vitrified and thus has a porous body with a high absorption rate. Despite its delicate nature, earthenware is surprisingly resistant to thermal shock, making it practical for both cooking and food storage. Throughout history, it has played a significant role in cultures worldwide, appearing in forms ranging from traditional handicrafts to ceremonial art across every continent.
It's also worth noting that the term "terracotta" is often used specifically for unglazed earthenware. Ultimately, the defining features of earthenware are its low firing temperature and the necessity of glazing to achieve a waterproof finish.
Porcelain
A white ceramic ware that is made of kaolin or China clay, which contains a large percentage of vitreous substances, such as feldspar and quartz. The high firing temperatures, generally ranging from 1200 to 1400°C, is crucial in giving porcelain its exceptional strength and characteristic translucency, allowing light to pass through, and it's very low water absorption rate. Another distinguishing characteristic is the clear, resonant sound it produces when tapped, often compared to that of metal.
Stoneware
A vitrified ceramic ware whose body color is not pure white. It is fired at high temperature of around 1100℃. Due to its hardness and density, stoneware is quite durable and resistant to chipping and breaking, making it well-suited for everyday use. It features an opaque body and offers good heat retention properties. While some stoneware pieces remain unglazed, glazing is a common practice to enhance their visual appeal and further improve their waterproof qualities.
Pottery Fabrication Techniques and Methods
Shaping of clay can be done in various ways, which can be chosen according to the characteristics of the clay (prepared clay ready for working) and the desired form.
Pinching
Hand-building is a fundamental pottery technique that involves shaping clay with your hands, without the use of a potter's wheel or molds. This is the earliest pottery forming method, dating back to the Neolithic period.
The process typically begins with a ball of clay, which you gradually shape into a pot or other vessel by pinching the clay between your fingers and thumb. As you work, you rotate the piece to ensure an even thickness of the walls.
This technique is especially accessible for beginners and offers a wonderful introduction to the tactile experience of working with clay.
Coiling
a handbuilding pottery technique where forms are constructed by building up walls with ropes of clay. These coils are carefully stacked upon one another and joined together by firmly pressing or "luting" them together. This process begins with shaping a base, followed by the gradual addition of coils. Each coil is then bonded to the one below with a pinching motion, ensuring a strong and lasting structure.
Wheel throwing
Placing a mound of clay on the wheel and lifting up the walls by using the speed of rotation and hand pressure.This process involves centering the clay on the wheel, then using hands and tools to mold it into symmetrical shapes, like bowls or mugs etc. The rotating wheel provides a dynamic element, allowing the potter to control the clay's shape and form, creating a variety of ceramic pieces. Trimming of the surface using the wheel is distinguished from throwing.
Molding
Press molding is where clay is forced into a mold to replicate its shape. Slip casting, refers to liquid clay (slip) being poured into a mold to form a layer on its inner surface. Slump molds are also used to create bowl-like shapes by draping a slab of clay over the mold's surface. Pouring or pressing clay into a terracotta, plaster or wooden mold. It is suitable for mass production or making sculptural, complex forms.
Slab building
Flat sheets of clay, called slabs, are cut and joined together to create 3D ceramic forms. It's a versatile method for making angular shapes and intricate designs that can be challenging to achieve on a pottery wheel.
Decorative Techniques
Slip coating
Slip, a liquid mixture of clay and water, is used in pottery for decoration, texture, and joining. This clay slurry can be painted, trailed, or dipped onto pottery, often before glazing, either as a base or a decorative element. When the clay body's color is undesirable, a white slip is often applied before a transparent glaze and firing
Painting
Underglaze
A technique where pigments are applied to the clay surface before it is glazed, at the green-wear or bisque-wear stage, allowing for vibrant, durable designs that are permanently fused into the piece. Unlike glazes, which may change color or become translucent, underglazes retain their original color intensity and often have a matte finish.
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​Overglaze Enameling
​Where colored designs or patterns are applied to a finished glazed surface, then fixed with a third, lower-temperature firing at 700-800°C. This process allows for a wider range of vibrant colors and intricate details that might not be achievable with underglaze techniques. This method allows for a more diverse color palette, including vivid colors and metallic effects like gold or silver luster, which may not be possible with underglaze techniques that require higher firing temperatures.
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Oxide Wash
A glazing technique where metallic oxide washes are applied to an unfired, usually white, glaze to create color variations and designs. These oxides, like iron, copper, and cobalt, react with the glaze during firing, resulting in different colors and shades. This method is commonly used in majolica and other decorative pottery styles.
Carving
Usually performed at the leather hard stage
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Intaglio
carved into the surface of the clay before it's fired, creating a negative space that will be filled with a contrasting material, like a different color clay or glaze. The resulting effect is a raised or recessed design that stands out from the background.
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Relief decoration
​Decoration represented in low relief by carving away the background.
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Sgraffito
A contrasting color (like a colored slip) is applied to a leather-hard clay piece, and then the top layer is scratched away to reveal the clay body or an underlying layer of color. The word "sgraffito" comes from Italian, meaning "to scratch".
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Piercing
a decorative technique where holes or patterns are created by carefully cutting right through the surface of a clay pot.
Impressing
Also known as stamping or embossing, is a decorative technique where a pattern or texture is created by pressing objects or tools into the soft clay surface. This process leaves a relief design, a raised or indented pattern on the clay, which can be used for both decoration and to add texture.
Sprigging
A pottery technique where low-relief designs are applied to greenware before firing usually at the leather hard stage. These designs, called "sprigs," are created by pressing clay into molds and then attaching them to the pot.
Slip trailing
Where thick, liquid clay (slip) is squeezed onto a wet or leather-hard clay surface using a fine-tipped applicator, like a syringe or squeeze bottle. This creates raised lines or patterns that can be colored to add texture and visual interest.
Inlay
Where contrasting colors or materials are embedded into a ceramic surface to create designs. This is achieved by incising grooves or carving designs into the clay and then filling them with different colored clay, slip (a diluted form of clay), or even underglaze.
Clay marbling
Also known as agateware (mimicking the appearance of agate stone), involves combining different colors of clay to create swirling, marbled patterns on a pottery piece. This can be achieved by layering different colored slabs of clay and then wedging or rolling them into a desired shape, or by using a slip marbling technique.
Gilding
Applying a thin layer of gold or gold-colored substance to the surface of the pottery, creating a decorative and luxurious look. This technique can be achieved through various methods, including applying gold leaf to an adhesive or using gold-colored paints and glazes.