Guide to Ceramics: Types, Materials, & How
Traditional types of ceramic pottery
Common examples are earthenware, stoneware, porcelain, and bone china. Clay is one of the widely available raw materials for creating ceramic objects. Different types of clay and combinations of clay with different variations of silica and other minerals result in different types of ceramic pottery.
Earthenware
Earthenware is pottery that has not been fired to vitrification, which is the process of crystalline silicate compounds bonding into noncrystalline glass compounds. This makes the pottery more porous and coarser to the touch. Earthenware pottery was the most common type of ceramics until the 18th century. Terracotta, a clay-based and unglazed ceramic, is a common type of earthenware. Today, we commonly see planters made from terracotta, along with bricks, water pipes, and more.
Stoneware
Stoneware is a vitreous or semi-vitreous ceramic, meaning it is coated in enamel to make it appear glassy and to make it nonporous. Stoneware is fired at high temperatures compared to other ceramics. It is typically an earth tone color because of impurities in the clay and is normally glazed.
Porcelain
Porcelain ceramics are made by heating materials, generally kaolin clay, in a kiln to temperatures between 2,200 and 2,600 degrees Fahrenheit. Porcelain is a very heat-resistant and strong material compared to other types of ceramics. This is because of the vitrification process and formation of the silicate mineral mullite when fired. Common types of porcelain ceramics are bathroom and kitchen tiles, vessels, decorative sculptures, and more.
Bone china
Bone china, also known as fine china, is a type of porcelain that is known for its translucency, high strength, and chip resistance. It is made from a combination of bone ash, feldspathic material, and kaolin, and was developed by English ceramicist Josiah Spode around 1800. Because it is such a strong material, bone china ceramics can be shaped into thinner forms than porcelain. It is vitrified but is translucent due to differing mineral properties.
Ceramics throughout history
The oldest known ceramics
The oldest ceramics that have been found date back to at least 25,000 BC. Uncovered in Czechoslovakia by archaeologists, these ceramics were in the form of animal and human figurines. They were made from a mixture of animal fat, bone, bone ash, and clay and were fired in ground kilns at low temperatures around 1000 degrees Fahrenheit, or simply dried in the sun to harden.
First functional ceramic vessels
The first examples of functional ceramics vessels are believed to be from about 9,000 BC and were likely used to store food, grains, and water. This was also around the time that small farming communities became more common in Asia, the Middle East, and Europe.
Decorative glazes and surface design
Early ceramics were generally simple in design and texture and were fired without glazes. In the 6th and 5th centuries BC, Greek Attic vases showed the first known use of oxidizing and reducing atmosphere during firing to achieve surface patterns and varying colors.
The invention of the wheel
One of the first breakthroughs in the fabrication of ceramics was the invention of the wheel in 3,500 BC. It allowed potters to go beyond the restrictions of hand building, and to dive into creating pieces with radial symmetry.
The introduction of porcelain
Around 600 CE, Chinese potters introduced high-temperature kilns and developed porcelain from kaolin clay, which is also known as China clay. This opened up possibilities for less porous and much stronger ceramic vessels. Throughout the 16th century, low fire earthenware remained the most common type of ceramic in Europe and the Middle East. It was not until the Middle Ages that trade through the Silk Road allowed for the introduction of porcelain and high-temperature kilns throughout Islamic countries and Europe.
Modern-day ceramics
Over the course of thousands of years, the ceramic industry has undergone a huge transformation. After World War II, ceramics contributed to the expansion of technology, electronics, medical equipment, transportation, and more. Today, you can learn ceramics for artistic or practical purposes.
How to learn ceramics
The Crucible offers a unique place to learn the different ceramic and pottery building techniques of pinching, coiling, and using slabs, in addition to press molds and slip casting with plaster molds. Students have the opportunity to explore different glazing techniques in low fire, high fire, and other firing alternatives, such as raku firing. Functional tableware, vessels, sculpture, installations, and mixed media—the possibilities in ceramics are endless for youth and adults of all levels.
Types of ceramic materials
Ceramics are omnipresent from our kitchen pantries to tool closets. They go far beyond the simple use of a ceramic vessel or sculpture and are applied in everything from science to mechanical engineering.
Ceramics FAQs
What is the cone system used to measure kiln firing temperatures?
The cone system measures how hot the kiln is and how long the clay body is fired in the kiln. Cones are essential when firing so that you know when your kiln has reached the necessary temperature and if the kiln was evenly heated. Each cone has a number assigned to it that corresponds to a specific temperature range. For example, cone 03 indicates a temperature range of about 1960 to 1987 degrees Fahrenheit.
Cones are placed in the kiln when firing to absorb heat, and as they reach the desired temperature, the tip begins to bend. You can watch the cones through the window in your kiln to make sure the kiln is heated evenly and the temperature is being reached.
What does it mean if clay or glaze is low, mid, or high fire?
Low fire clay fires in the kiln between 1940-2109 degrees Fahrenheit. The pro of low fire clay is that it is easy and economical to fire, however, it is porous and not the best option for liquid-bearing vessels. Mid-fire clay fires between 2157-2232 degrees Fahrenheit, making it easily fired in an electric kiln. It is a versatile clay, strong once fired, and not porous. High fire clay fires at about 2381 degrees Fahrenheit. It is durable and waterproof, making it a long-lasting and strong option. The downside of high fire is that it is best to fire it in a gas kiln, making it less accessible to most potters.
What are reduction and oxidation and what do they do?
Oxidation and reduction refer to how much oxygen is present in the kiln when the clay is fired. An oxidized atmosphere has lots of oxygen, while a reduced atmosphere has very little. This can change the texture of your clay and interact with specialty glazes.
What is the difference between using a gas kiln and an electric kiln?
Electric kilns are more common in both home and professional studios because of ease of convenience and setup. Electric kilns work well for low and mid-fire clay, while gas kilns work for high-fire clay. Compared to gas kilns, electric kilns do not require special permits. Gas firings generally result in earthier colors and can be used in reduction firing to achieve interesting surface textures.
What are the safety concerns for using clay? Can I use it safely at home?
When you are working with clay, one of the most important precautions is to protect yourself from inhaling the powder that results from dried clay. This contains silica, which can hang in the air for hours and can damage your lungs. In order to protect yourself, wear a mask, understand what ingredients are in the clay you are using, and use premixed, wet clay bodies.
What are Ceramics
From a chemical point of view, ceramics are defined in terms of what they are not. They are non-metallic and inorganic solids – in other words, what we are left with when we take away metals and organic materials.
For many people, ceramics mean things like tableware, roof tiles, flowerpots, coffee cups, bricks in a fireplace, or a pizza oven or tiles on a kitchen wall. These products are known in the industry as traditional ceramics.
But beyond these everyday household items, there exist various other cases where ceramics are used.
Refractories as a part of ceramics are used as a refractory material because of their resistance to heat, mechanical stress or chemicals. Since they keep their shape and strength at high temperatures, they are used in all extreme-temperature industrial processes, primarily in metallurgical processes but also cement, glass, energy, chemical processes and more. Refractory ceramics are constantly innovating in close cooperation with these high-temperature processes to support their transformation, and a strong and autonomous European industry cannot be conceived without refractories.
Technical ceramics are considered to be one of the most efficient materials of our time. They are applied in many industries and include established products, such as insulators, engine parts, catalyst carriers, bone replacement, filters, and many others.
Technical ceramics are an active contributor to the well-being and construction of a resilient, carbon-neutral European society, and to achieving the goals and objectives of the EU Green Deal.
Technical ceramic components can tolerate higher temperatures and loading forces with a significant increase in the number of successful run cycles when compared to traditional materials. This means a considerable enhancement of efficiency, which is often a key factor in the indication of sustainability.
This process creates commercial products that are diverse in size, shape, detail, complexity, material composition, structure and cost.
Ceramic products that use naturally occurring rocks and minerals as a starting material must undergo special processing in order to control purity, particle size and particle size distribution.
These attributes are integral to the final properties of the finished ceramic.
Chemically prepared powders are also used as starting materials for some ceramic products. These synthetic materials can be controlled to produce granules or powders with precise chemical compositions and particle size.
The next step is to form the ceramic particles into a desired shape. This is accomplished by the addition of water/steam and/or additives such as binders, followed by a shape-forming process.
Some of the most common forming methods for ceramics include pressing, slip casting, extrusion, tape casting and injection moulding. More recently, we have observed a growing use of ceramic 3-D printing in technical ceramic applications with benefits not only in terms of functionalities but also in terms of resource efficiency.
The products are dried and heated to produce a rigid, finished product. Some ceramic products such as electrical insulators, dinnerware and tiles may then undergo a glazing process. Ceramics for advanced applications may undergo a machining and/or polishing step to meet specific engineering design criteria.
