Ceramics – basics and composition
Ceramics is a general term for a hard and durable, yet relatively brittle material used to produce all traditional pottery and tableware, regardless of the exact manufacturing process or combination of ingredients. All ceramic materials (including terracotta, earthenware, stoneware, faience, and porcelain) are made from clay, which primarily consists of aluminium oxide, silicon dioxide, and water.
Other elements, such as potassium oxide and iron oxide, may be naturally present depending on the type of clay. Manufacturers may also add these and other minerals or substances to the clay mixture to achieve specific properties, such as a smoother texture, a particular colour, or increased resistance to breakage. These are known as additional compounds (sometimes referred to as inclusions).
Everything from the grain size of the clay to its water content affects the physical characteristics of the material, including colour, plasticity, porosity, and firing behaviour. The specific combination of ingredients used for a given type of clay is known as the clay body.
How is ceramic tableware made?
Individual ceramic pieces are shaped from the clay body, either by hand or mechanically, into the desired form – whether a plate, bowl, cup, tray, or another type of tableware. Each piece then goes through one or more firing processes at temperatures well above 550°C (around 1,000°F) in a specialised oven called a kiln.
Exposure to high temperatures causes a physical transformation that makes the clay hard, durable, and resistant to moisture.
Depending on the desired result, each ceramic piece is usually coated with a glaze, either before or between firing stages. Because many types of clay retain a certain level of porosity even after firing, the glaze seals the surface and prevents the tableware from absorbing moisture from food and drink.
Manufacturers may use transparent glazes when they want the natural colour of the fired clay to remain visible. In most cases, however, glazes become opaque during firing and are chosen for the decorative, coloured finish they give to the final piece.
Vitrification – what does “vitrified” mean?
Many types of ceramics are fired at very high temperatures and held there long enough for the clay to become partially or fully vitrified. Vitrification is the process by which ceramics reach a point of partial melting. At these extreme temperatures, clay and minerals fuse together, forming a dense, crystalline, glass-like structure.
The term comes from the Latin vitreum, meaning glass, because this process gives the clay glass-like properties. This transformation significantly strengthens the material and makes it far less porous than non-vitrified ceramics. In some cases, fully vitrified pieces do not require glaze for sealing purposes, as the glaze becomes purely decorative.
Earthenware, stoneware, and porcelain – what’s the difference?
Different clay bodies and firing processes give ceramics different properties. These physical characteristics determine how each type is used, how its quality is perceived, and its overall value. Despite their differences, all of these products share one thing: they all begin as clay – which means they are all ceramics.
Terms such as earthenware, stoneware, and porcelain refer to specific types of ceramics with distinct physical properties, appearance, and levels of porosity.
Porosity – the key difference
One of the most important differences between ceramic types is porosity, or water absorption. According to international ASTM standards, porosity is measured by immersing a ceramic piece in boiling water and then leaving it in room-temperature water for several hours. The difference between dry and wet weight shows how much water the piece absorbs.
Based on these measurements, ceramics are broadly classified as:
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Porcelain and fine china: absorbs less than 0.5% of its weight in water
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Stoneware: absorbs less than 3%
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Earthenware: absorbs more than 3%
These measurements are important because water absorption directly affects durability and prevents lower-quality ceramic products from being incorrectly labelled.
Modern, high-quality manufacturers often exceed these standards. For example, Costa Nova stoneware achieves water absorption below 0.3%, which is stricter than the typical limit for classic porcelain. In practice, this means premium stoneware behaves like a professionally vitrified material, ideal for serious hospitality use.
Common ceramic types found in kitchens and restaurants
Earthenware
Earthenware is the most basic type of ceramic. Compared to other types, it is usually made from the least refined clay bodies and fired at the lowest temperatures, using a process similar to prehistoric pottery techniques.
Because of this simple process, earthenware must be relatively thick to maintain durability and is highly porous. It must be fully glazed if intended for contact with food or liquids.
Terracotta is a common example of earthenware. A terracotta flowerpot clearly illustrates how fragile it can be and why it is rarely used for food service.
Due to its porosity, chipped or cracked earthenware can quickly absorb water and food residue, which may lead to bacterial growth. For this reason, earthenware is rarely used in professional hospitality settings, except occasionally as decoration.
Stoneware
Stoneware is a relatively modern development and represents a significant technological advancement over earthenware. It is more durable and far less porous, allowing pieces to be thinner and lighter. Almost all restaurant tableware that is not classified as porcelain is produced as stoneware.
Stoneware is fired at high temperatures to achieve a strong, durable finish and is known for its earthy, rustic appearance, which brings warmth and authenticity to the table.
It is typically fired to a semi-vitrified or fully vitrified state and often has a creamy or off-white base colour. Manufacturers may use transparent glazes to highlight the natural body colour or coloured glazes with decorative effects. The most durable stoneware is labelled as fully vitrified.
Premium manufacturers such as Costa Nova develop carefully engineered clay bodies and fire them at very high temperatures, achieving extremely low water absorption (<0.3%). This makes stoneware suitable for fine dining, luxury restaurants, villas, boutique hotels, and gastro bars seeking a natural look with professional performance.
Advantages of stoneware
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High durability and resistance to chipping
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Excellent heat retention
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Versatility (often suitable for ovens, microwaves, and dishwashers, depending on manufacturer specifications)
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Easy maintenance when vitrified
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Strong value over time due to long lifespan
Limitations of stoneware
Stoneware can be slightly heavier than porcelain, and over time may show subtle signs of wear from cutlery. This does not affect functionality, but may matter for those who prioritise a pristine appearance.
Porcelain and “china” – what’s the difference?
The term “china” is often used loosely to describe ceramic tableware in general. Formally, it usually refers to a partially or fully vitrified material made primarily from fine white kaolin clay.
Because kaolin was first discovered and used extensively in China, and China was historically the largest producer of fine porcelain, the term “china” became synonymous with higher-quality ceramic tableware.
What is porcelain?
Porcelain is a ceramic fired at very high temperatures (typically 1,250–1,350°C) and made from:
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Kaolin – provides whiteness, strength, and heat resistance
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Feldspar – melts during firing and binds the material, creating a dense, glassy surface
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Quartz (silica) – improves thermal resistance and reduces shrinkage
This produces a vitrified, semi-translucent ceramic that is stronger than it appears.
Modern commercial porcelain, such as that produced by Costa Verde, combines traditional porcelain bodies with advanced firing and glazing techniques to deliver durability, colour stability, and professional hospitality standards.
Choosing ceramic tableware for hospitality
When selecting tableware for a restaurant or hotel, consider:
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style and concept
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intensity of use
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service volume
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guest expectations
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washing, storage, and logistics
Stoneware and porcelain are not “better” or “worse” than one another. They are different answers to different needs.
In premium environments, the most refined solution is often a combination:
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stoneware for emotion, character, and signature presentation
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porcelain for precision, uniformity, and high-volume service
This balance defines contemporary luxury: not uniformity, but consciously curated choice.