Where Do We Get Ceramic?
Ceramics refer to objects made from inorganic, non-metallic materials that are permanent after being exposed to heat. The word “ceramic” comes from the Greek word keramikos, meaning “potter’s clay” or “pottery”. Ceramics have been an integral part of human civilization for thousands of years, with the earliest known ceramic objects dating back over 20,000 years. Some major examples of ceramics include pottery, tiles, bricks, and porcelain.
The ancient history of ceramics begins with the discovery of fire and pottery around 24,000 BC. Pottery shards from Jōmon Japan date back to 14,000-300 BC, and fragments from Xianrendong Cave in China date between 20,000 to 10,000 BC. The Venus of Dolní Věstonice, a ceramic figurine from the Czech Republic, dates back to 29,000–25,000 BC. Ceramics allowed early civilizations to store and transport food, water, and other goods more easily. Ceramic art, sculpture, and architecture flourished in ancient Greece and Rome. Porcelain originated in China around the 7th century AD during the Tang dynasty. The Silk Road facilitated trade of ceramics across Europe and Asia from the 9th to 15th centuries. While largely utilitarian for most of history, ceramics evolved into an artform by the 19th century, alongside innovations in glazing and firing techniques [1].
Today, ceramics are found in countless aspects of human civilization, from dishes and cookware, to tiles and electronics. We continue to discover new ceramic formulations and applications in fields like engineering, medicine, and environmental science.
[1] https://ceramics.org/about/what-are-engineered-ceramics-and-glass/brief-history-of-ceramics-and-glass
Raw Materials for Ceramics
Ceramics are made from a combination of raw materials including clays, silica, feldspars, and quartz. The three main components are clay, silica, and flux. Clay is the main plastic ingredient and provides shapeability. Silica is the glass former and provides strength and durability. Flux helps lower the melting temperature and promotes glass formation. Some common raw materials used in ceramics include:
Clay – Clay is the most common plastic ingredient used in ceramics. It provides shapeability and plasticity when mixed with water. Common types of clay used include kaolin, ball clay, and bentonite (Source).
Silica – Silica provides the glassy phase in ceramics and improves strength and durability. Quartz is a common source of silica for ceramics. Other sources include flint, silica sand, and ground quartz (Source).
Feldspars – Feldspars act as flux to lower the melting temperature. They promote vitrification and glass formation. Common feldspars used include potassium feldspar and sodium feldspar.
Quartz – Quartz improves resistance to thermal shock and chemical attack. It increases mechanical strength and stability of the ceramic body.
These raw materials are precisely measured, mixed, and shaped into the desired ceramic products. The raw material composition influences the final properties and performance of the ceramic.
Clay
Clay is the primary raw material used in ceramic production. Clay is composed of hydrated minerals like feldspar and kaolinite that provide plasticity when mixed with water. The main types of clay used in pottery are earthenware clay, stoneware clay, ball clay, fire clay, and porcelain clay.
Earthenware clay is very porous when fired at relatively low temperatures like 1800°F. It has a coarse texture and absorbs water easily, making it easy to work with (“Types of Clay for Pottery – The Main Clay Types”, n.d.).
Stoneware clay becomes vitrified and non-porous at higher firing temperatures between 2200°F-2400°F. The feldspar content in stoneware clay causes the vitrification. Stoneware has low plasticity and absorbs little water (“Types of Clay for Pottery”, 2020).
Ball clay is very plastic and sticky, providing strength when added to other clays. Ball clay is added to stoneware and porcelain to improve workability. The name comes from how it is mined in balls or chunks (“Types of Clay for Pottery”, 2020).
Fire clay can withstand extremely high temperatures above 2300°F before vitrifying. It has high amounts of alumina and silica. Fire clay is often added to stoneware and porcelain mixes (“Types of Clay for Pottery – The Main Clay Types”, n.d.).
Porcelain clay becomes translucent white when fired between 2200°F-2400°F. It is made from kaolin clay and is smoother and less porous than other clays (“Types of Clay for Pottery”, 2020).
Most clay deposits were formed from the weathering of feldspar-rich rocks like granite. Clays are mined from open-pit mines and underground mines around the world.
Glazes
Glazes are an important component of ceramic ware as they provide a durable, glassy coating that makes the piece impervious to liquids and protects the clay body underneath. The main purposes of ceramic glazes are decoration, color, and surface protection.
Glazes are composed of silica, fluxes, and stabilizers. Silica provides the glassy base, fluxes lower the melting point of the glaze so it vitrifies at kiln temperatures, and stabilizers prevent leaching, crawling, and crystallization. Common raw materials used in glaze recipes include feldspar, quartz, kaolin, whiting, dolomite, and ball clay. In addition to natural materials, some glazes incorporate man-made materials like frits, stains, and zirconium silicate.
Glaze recipes must be carefully formulated and tested to achieve the desired characteristics in terms of color, texture, melting temperature, thermal expansion, and more. Factors like clay body, kiln temperatures, and firing atmosphere impact how a glaze melts and vitrifies during firing. Master potters often spend years perfecting their glaze recipes and techniques through extensive testing and observation.
Firing Process
The firing process is a crucial step in ceramics where the clay and glazes are hardened through exposure to high temperatures. There are several types of kilns used for firing ceramics:
Electric kilns are often used by hobbyists, small studios, and schools. They provide precise digital control over temperature. Gas kilns utilize propane or natural gas to generate heat and are preferred by some artists for providing atmospheric effects. Wood-fired kilns use wood as fuel and create unique natural ash effects on the surface. Dual media kilns can fire ceramics up to 2350°F and accommodate glass as well [1].
During firing, clay undergoes irreversible physical and chemical changes. As temperature rises, clay particles bond together permanently in the process of sintering. The firing process vitrifies the clay, driving out water and organic compounds to create a dense, non-porous material. Maximum firing temperature determines the strength and other properties of the finished ceramic piece.
There are several standard firing temperature ranges corresponding to cones. Low-fire clays mature at lower temperatures up to 2,065°F (Cone 04-06). Mid-range firings for stoneware and porcelain reach 2,200-2,360°F (Cone 4-7). High-fire temperatures exceed 2,300°F (Cone 8-10) and result in more durable ceramics [2].
Forming Methods
There are several techniques used to shape ceramics into various forms and products. Some of the main forming methods include:
Throwing
Throwing is one of the most common ceramic forming techniques and involves using a pottery wheel to shape clay into symmetrical objects like bowls, cups, vases, and plates. The clay is centered on the wheel and then manipulated by the force of rapid spinning as well as the potter’s hands.
Slip Casting
Slip casting involves pouring liquid clay slip into a plaster mold so that clay coats the inside of the mold and forms the desired shape as it dries. Once dried, the excess clay is poured out of the mold. Slip casting allows for mass production of intricate, detailed ceramic pieces. [1]
Pressing
Pressing involves compacting clay in a mold using pressure. The clay is rolled out into sheets and then pressed into molds. An example is dry pressing, where clay powder is poured into a mold and compacted. This allows both small and large scale production.
Extrusion
In extrusion, clay is forced through a shaped opening or die. The continuous lengths or slabs produced this way can be cut to size. Extrusion allows for making pipes, rods, bars, and tubes.
Decorating
Ceramics can be decorated in various ways to enhance their aesthetic appeal. Some of the most common decorative techniques include:
Glazing – Ceramic glazes are glass-like coatings applied to biscuit fired pottery to create a waterproof surface and decorative effects. Glazes come in endless colors and textures and can be applied by brushing, dipping, or spraying. Glazes melt during firing to produce glossy or matte surfaces.1
Painting – Ceramic painting involves applying colored slips, engobes, underglazes, and overglazes to leather-hard or bisque fired ceramics. Popular techniques include brushwork, sponging, stippling, blending, and airbrushing. Paints chemically bond to the clay during firing.2
Staining – Ceramic stains contain metal oxides that are painted onto bisqueware and absorb into the clay body to create colorful designs. Common stain colors include black, brown, blue, green, yellow and red.
Printing – Printmaking techniques like screen printing, decal application, and stamping can be used to transfer images and patterns onto ceramic surfaces. Printed decorations are sealed by firing clear glazes over them.
Notable Production Centers
Some of the major regions known for ceramic production include:
China is the world’s largest producer and exporter of ceramic tiles. According to Statista, China produced around 7.31 billion square meters of ceramic tile in 2022. The main ceramic tile production centers are located in Guangdong, Fujian, and Shandong provinces.
Italy has a long tradition of ceramic production, especially in centers like Sassuolo and Civita Castellana. Italian manufacturers are known for their innovative design and style. Major Italian ceramic tile brands include Marazzi, Florim, and Panaria.
Japan has a ceramic history stretching back over 12,000 years. Major production areas include Seto, Tokoname, and Arita. Japanese ceramic styles like Imari porcelain and Kakiemon are famous worldwide.
Mexico is one of the top producers of ceramic tile in North America. The main area of production is in Jalisco state. Mexican ceramic tiles are known for creative designs and bright colors.
Modern Ceramic Uses
Ceramics play an important role in modern society with a wide variety of applications. Some of the most common uses of ceramics today include:
Pottery – From decorative vases and bowls to tableware, ceramic pottery remains an popular artform and household item. Modern pottery uses refined clays, glazes, and kilns to create beautiful objects.
Floor and Wall Tiles – Ceramic tiles cover floors, walls, countertops, and other surfaces in homes and buildings. Tiles are durable, easy to clean, and come in a vast array of styles and designs.
Advanced Ceramics – Engineering ceramics possess exceptional mechanical properties and heat resistance for use in automobiles, electronics, aerospace components, medical implants, and more (Traditional and Modern Uses of Ceramics, Glass and Refractories).
Abrasives – Ceramics like silicon carbide and aluminum oxide are very hard, making them ideal for grinding and polishing applications.
Refractories – Ceramics withstand very high temperatures, so refractory ceramics are used to line high-temperature kilns and furnaces.
While retaining their traditional uses, ceramics continue to enable new technologies and drive innovation in manufacturing and construction.
Future of Ceramics
The future of the ceramic industry looks promising due to innovations in materials, manufacturing processes, and sustainability efforts. According to the April 2021 issue of ACerS Bulletin, additive manufacturing is driving advances in the ceramic industry by enabling more complex shapes and microstructures.
Ceramic manufacturing is also becoming more automated, leading to increased consistency and efficiency. Companies are exploring new ceramic materials like nano-ceramics that have enhanced properties. There is also a push towards more sustainable production methods and recyclable ceramic products.
Growth areas for ceramics include electronics, energy storage, healthcare, and construction. Ceramic components are being used more frequently in electronics due to their insulating and piezoelectric properties. The construction industry is utilizing advanced ceramic coatings and additive manufacturing for buildings. Overall, innovations in materials and manufacturing will enable ceramics to meet the demands of modern technology and sustainability.
