CERAMICS

Ceramics is one of the earliest forms of artistic expression used by mankind.

It is a way to connect with the clay of mother earth, not only to create functional objects, but also ceremonial ones.

A link with our origins where artistic beauty, practical utility and religion can come together.

Here we solve the doubts that you usually have about this subject and we explain everything you need to enter this fascinating world.

ORIGIN OF CERAMICS

The term pottery comes from ancient Greece and was the name of a popular neighborhood in Athens where a large number of potters lived, or what today with this new term we would also know as potters.

The words pottery and ceramics are used interchangeably and can be considered synonyms although there is still some debate as to whether there are differences between the two, we will clarify this issue below.

Humans have used fired clay since before metal. One of the oldest surviving pieces of pottery is a bowl found in Jiangxi province, southern China, dating back 20,000 years and some place the famous Dolní Věstonice venus made in terracotta as early as 29,000 BC.

WHAT IS CERAMICS?

What defines the term ceramic in terms of material is the fact that it was created from clay with a subsequent firing.

It also refers to the work of the potter, to the craft of creating this type of baked clay objects.

The concept of clay implies a series of specific characteristics, such as being the product of the decomposition of rocks and being made up of very fine particles (less than 0.004 mm in diameter), although the requirement to be a raw material used in ceramics can be extended to any mixture of non-metallic inorganic material susceptible to heat treatment.

This very fine thickness of the clay “grains” is the key to its behavior as a mass, bound by the water it contains, which is why sand is not clay even though it may also contain water, since the particles are coarser and disintegrate.

A consequence of the fineness of its particles is that during firing they will fuse together to form a rigid unit or block.

There is a wide variety of types of clays used, including mixtures of materials obtained by various processes, which could be called synthetic clays.

Taking into account in the definition of clay the requirement of coming from the sedimentation of matter coming from rocks of the Earth, some synthetic materials, which are also fired in a kiln, would not be clay and therefore not ceramic, as is the case of those based on PVC, such as polymer clays.

Ceramics is also called the process of manufacturing any type of object from clay and its subsequent firing or heat treatment.

Ceramics understood in a broad sense are not only artistic pieces, works of pottery or tiles. Its application in industrial areas has been increasingly implemented in recent decades since the 1970s, thanks also to the development of new manufacturing techniques. In the United States alone, the advanced ceramics industry is worth more than $13 billion.

THE DIFFERENT TYPES

While many of the materials and techniques remain largely unchanged today, their rich history means there is a lot of terminology to contend with. With a range of firing methods and an even wider range of different clay varieties, for many of us with limited knowledge, it can be confusing.

Although all traditional pottery is clay-based and most varieties are kiln-fired, the type of clay used and the temperature at which this clay is heated produce very different effects. It can sometimes be difficult to determine exactly which category your pottery falls into.

Three main categories of ceramics are usually determined (although there are more classes and subclasses), these are:

• Earthenware
• Stoneware
• Porcelain

The composition of the clays used, the type of additives and the firing temperatures determine the nature of the final product.

You can find more information in our guide to ceramic types.

There is also an “advanced” or industrial ceramic that takes into account the strongest and most resistant components known. These ceramics are often used in the manufacture of consumer products, construction, scientific equipment and machinery, cars or vehicles, and many others.

Nowadays, the term ceramic has a broader meaning and sometimes takes into account various materials such as glass, cemented materials and ceramics for industrial and technological applications.

WHAT IS THE STRONGEST AND HARDEST CERAMIC?

Depending on their composition, structure and processing, very different ceramic materials can be obtained, we explain their characteristics and applications, some of which are surprising!

INCLUDING ALL MATERIALS OF THE CERAMIC INDUSTRY

The hardness and strength of the ceramic depends on the specific composition and the manufacturing process used. Ceramics with a high content of silicon carbide, aluminum oxide or silicon nitride withstand wear and high temperatures well.
Silicon carbide ceramics are known for their hardness and abrasion resistance, making them ideal for use in applications such as ball bearings and brake discs.

Aluminum oxide ceramics are also very hard and are often used in cutting tools.

Las cerámicas de nitruro de silicio tienen una gran resistencia al desgaste y pueden soportar altas temperaturas, por lo que son útiles en piezas de motores y bolas de cojinetes.

Zirconia composite ceramics withstand impacts well. This material is used in bulletproof vests and shields.

It should be noted that although these ceramics can be very hard and wear resistant, they can also be brittle and prone to cracking or breaking under strong impact or stress.

This material is also very resistant to extreme temperatures, which is why it is used in rocket engines to protect them and in other areas such as the base of launchers to insulate against the high temperatures generated during re-entry into the Earth’s atmosphere.

The strength of a ceramic material is determined by its microstructure and the type and number of bonds between particles. Factors such as the purity of the constituent materials, the presence of defects or impurities and the temperature and duration of the firing process determine the strength of the final ceramic product.

WHICH IS THE HARDEST HOUSEHOLD CERAMIC?

As for household ceramics, depending on the composition, temperature and firing time, we would have a “continuum” of resistance to impacts and scratches, ranging from terracotta or unglazed earthenware to high purity porcelain.

It should be noted that glaze is a glass-like material made of silica, alumina and other oxides. It is known for its durability and resistance to scratches, stains and odors and is often used for cookware and other household products.
Any unglazed ceramic will chip, crack and scratch relatively easily.

As for porcelain, it is made from kaolin, feldspar and quartz. It is known for its strength, hardness and wear resistance. Cookware and tableware made from porcelain are commonly used in homes for their durability and strength.

THE DIFFERENCE BETWEEN POTTERY AND CERAMICS

Although these terms are used to describe different types of household items or various artistic pieces, both pottery and ceramics mean the same thing. The two can be used interchangeably for anything that is formed from clay, then fired in a kiln and glazed or decorated according to the desired finish.

However, ceramics is a more general term that can include building components, floor tiles, roof tiles or sanitary ware.

While the term pottery is more restricted to popular tradition and culture, and to the work of making objects for food use, such as wine jugs, oil pots, etc.

Original artwork by Enrique Vásconez

CERAMICS AS ART

Of course it can be!, depending on the object created?, the process?

The process of working ceramics by hand modeling can be an art, influencing the psyche of the individual who “creates”. And the criteria for deciding whether the object created is an art object or not would already be somewhat arbitrary.

The fact that utensils are made with a practical character, as for example a jar, does not exclude that the object possesses a beauty that confers it the nature of an artistic object. However, we must agree that there is a certain difference between a handmade vase or a sculpture and a plug made in a mold (ceramics was a material quite used some time ago for its characteristic of insulating electricity).

For all these reasons, a distinct area will be all the work considered as ceramic sculpture.

There is a wide repertoire of methods and ways to create, whose differences are, among many others, in what technique the potter uses to treat the form, what method he uses to achieve the colors, or how to fire the clay, modifying the time and/or temperature of the clay.

In turn, the materials used, the function of the object created (artistic, functional, religious), its applications, or the styles employed define a wide range of ceramic classes.

CERAMIC MATERIALS

There are four main materials or elements:

• Clay
• The tools
• The potter’s wheel
• The kiln

THE CLAY

It is the raw material par excellence. It is abundant and accessible to obtain, with it a great majority of pottery works are produced.

However, although the vast majority of ceramic production is made with natural clay, there are many differences between the results obtained depending on the types of clays we choose.

To classify the materials used in ceramics, two criteria are usually used: one is the composition and the other is the application given to the piece.

Depending on the composition there are carbides, oxides, nitrides, sulfides, etc. This type of compound gives us materials such as ball clay or kaolin, which is highly prized and an essential component of porcelain.

Depending on the application or use of ceramics, we could speak not only of artistic ceramics, but also of industrial ceramics, which include abrasive products, cementitious products, so-called advanced ceramics (which are made of certain very specific compounds containing aluminum oxide or silicon carbide), refractory products (which withstand high temperatures and are also thermal insulators), etc.

You can read more in our publication on materials for artistic ceramics and pottery.

THE TOOLS

Before tools, the first thing used in pottery is proper clothing and often an apron.

Towels for cleaning and chamois cloths for smoothing surfaces will also be used.

Cutters (such as a fishing line held together by two pieces at the ends to cut large pieces of clay), as well as knives, are used as utensils.

Wooden tools, brushes, etc.

Measuring elements such as a caliper to see widths and thicknesses.

THE POTTER’S WHEEL

This element is millennia old. We have all seen it on many occasions and it is really hypnotic to see how it works.

It consists of a circular surface that is kept rotating while the part is being shaped.

First it was moved mechanically by hand or with a handle, then methods were devised to move it with the foot and thus both hands could be used continuously. Finally we have the electric lathes.

Lathe work requires a skill that takes years to learn and is difficult to master, requiring good fine motor skills.

In this incredible video you can see something you rarely get to see nowadays: A wonderful potter from India working clay with a single wheel, a chance to see how it was made thousands of years ago.

THE KILN

The first kilns consisted of holes in the ground, later different structures were built. Firewood and charcoal were used.

Then came fossil fuels such as oil and oil derivatives, and later gas.

Later we would have the electric ones, easier to use, to install and safer, they are manufactured with different designs and opening zones.

At all times we are talking about a kiln manufactured specifically for ceramics, a conventional kitchen kiln will not work.

AT WHAT TEMPERATURE THE CLAY IS FIRED

There are several types or phases of firing at different temperatures. When the pieces go through the kiln twice, it is in the second phase when there is a greater difference in temperature between the types of clay used.

Mono-firing:

If we cook the pieces only once, we would be talking about mono-cooking, which is not the most appropriate, since not all materials offer an optimum result and we obtain pieces that are too porous and are not suitable for culinary use.

Two-stage firing:

It is more common and recommended than the previous single process. These two phases are:

• Bisque: The clay is fired at around 1000º and we could already talk about ceramic, but it is still porous.
• Second firing: The temperature required by the material and the result we are looking for is used.

There is also a three-phase option, which is recommended if we have worked with materials such as grease or polishes.

For the second firing there are some guideline temperatures for different types of ceramics:

CERAMIC TECHNIQUES

The ceramist trade is as old as humanity itself, we can find an infinity of techniques that come from the mists of time, all of them ranging from the most basic, which is the modeling of the piece of clay with your own hands, to the most avant-garde that are used today benefiting from technology.

The techniques used to create from the initial clay can be grouped into those that apply to the shape (from the initial kneading of the clay to the final decoration), those that use color (with mixtures of different clays or already moving on to painting, glazing, etc.) and those that use the firing process as another artistic phase in which to achieve aesthetic effects, as in the case of Raku.

You can read all you need to know in our ceramic techniques section.

SUMMARY:

Here are some frequently asked questions about some of the main concepts:

You can also access some of our main ceramic guides below: