Terracotta – probably the oldest kind of ceramics
The name terracotta comes from Latin and is composed of the words terra (earth) and coquere (to boil) and means “boiled earth” or “fired earth”. Essentially, terracotta consists of clay as a shaping component and a small amount of feldspar to bind the mass. Unlike porcelain, the manufacturing process of terracotta does not prescribe a minimum temperature firing. This explains why there are so many different grades within this material definition. Low-fired terracotta, for example for building ceramics or low quality flower pots, obtains its final strength already at a firing temperature of about 650 °C. If the clay is “layered” with fireclay, the result is a denser consistency of the body and the terracotta can be fired at a higher temperature for more demanding use. This results, for example, in frost resistance for garden terracotta or greater resistance to impact.
The glaze is the decisive factor for the usability of terracotta products. Building and garden ceramics are often only finished with simple clay glazes, which the user likes to perceive as rough, unglazed surfaces. In fact, however, even such clay glazes create a higher density of the body and thus better durability. Unlike porcelain, terracotta is also suitable for so-called “cold painting”, i.e. an unfired application of colours and decorations. The finishes, usually applied as oil paints, are varied, vibrant and beautiful, such as most ceramic garden gnomes for outdoor decoration. Such colours adhere much better to the body than to porcelain, but are neither weatherproof nor UV-resistant.
Depending on the origin and colour of the terracotta clay and the subsequent intended use, many decorative items are also made from unglazed terracotta. Large planters of Mediterranean design, garden statuettes and figures made of red clay are particularly popular and widespread. The world’s most famous unglazed terracotta is probably the 8,000-strong Chinese terracotta army, created around 200 BC by the Qin dynasty and named the 8th wonder of the world.
Terracotta is particularly suitable for creative moulding and is often worked by hand. The Greek Tanagra figures made of terracotta date back to the 4th century B.C. The cradle of moulded, dried clay goes back to prehistoric times (about 2 million years B.C.) and is attested by excavations of small figures from this era.
The diversity of terracotta
In contrast to porcelain, which was mostly intended and produced for the better-off social classes, the production of terracotta is far less expensive and dedicated to “the common people”. It is a raw material-oriented craft that settled in Europe in the regions where suitable clay deposits could be found. Over the years, this craft developed into a small industry and gained its own profile. The Italian “Impuruenta terracotta” attributed a high frost resistance to its product, as the clay had a high mineral content and could be fired to a dense strength. Cheaper and lower fired was the “Siena terracotta”, which was also Italian. Around 1400 AD, terracotta production developed in Germany in the “Kannenbaecker Land”, a region in the Westerwald around Ransbach-Baumbach, Höhr-Grenzhausen and almost as far as Koblenz. There, mainly pipe bowls, oil lamps, vases, jugs and inexpensive table ceramics were produced, which were later developed into the so-called salt glaze. Probably the most consistent areas of origin for today’s utilitarian table and kitchen terracotta are the regions of “Roca in Catalonia” (Spain), Civita Castellana and Treviso (Italy), The Porto Region (Portugal), Batang (Vietnam), Lampang (Thailand), Fujian Province and Shanxi Sheng Province in China.
Due to globalisation and the transparency that comes with it, almost all companies are trying to develop their own individual product profiles for their terracotta and ceramics. Durability, size, colour, type of use and, of course, price are the main factors. To find one’s way through this almost infinite variety of possibilities is reserved for only a few experts. Within the framework of our “OEM business”, we realise many different contract productions in different countries, e.g.
- Pipe bowls
- Packaging for the food industry
- Ready to serve ice cream and dessert
- Fire pots
- Flower vases
- Bowls and dishes
- Plates and accessories for buffets
The specifications and requirements for the respective items determine the country of origin, region and manufacturing plant. To fully disclose this diversity here would not only go beyond the scope, but would also reveal an important competitive advantage of Holst Porcelain. However, the following generally valid basic rules can be assigned to terracotta.
- As a rule, the glaze firing is above the hard firing
- rom about 1,150 °C the clays of the terracotta melt and burn in the fire
- Terracotta is not thermal shock resistant
- Terracotta is not basically heat resistant (*)
- Terracotta is not basically ovenproof (*)
- Terracotta is not basically suitable for use with food (*)
(*) otherwise the terracotta is specially made for this purpose.
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Building Ceramics/Statuettes/Garden Ceramics
High quality garden terracotta, ornamental ceramics
Cooking & Oven Ceramics, Jugs,Tableware, Food Packaging
High-quality kitchen, table and tabletop ceramics
The classic terracotta from Holst Porzellan
Since many years are producing classic terracotta for the Mediterranean kitchen in the Mediterrano series. This is a clay-feldspar quality with a brick glaze that undergoes its second glaze firing at around 1,000°C. Glaze firing. This type of terracotta is suitable for use as a food contact item and complies with EU directives and LFGB regulations. The articles in this quality class are temperature-resistant up to 300 °C and are ideal both for preparing and gratinating food and for serving directly to the guest. The surface of the articles absorbs water and does not correspond to the density of porcelain. The edge impact strength of this ware is internationally defined as 0.04 joules (ft.ib.force).
However, due to the material composition and firing temperature, ceramic is by no means as robust as white hard porcelain. The typical red-brown brick glaze is a natural product and gives each bowl an individual appearance. Ceramics are much more sensitive and should only be used commercially with caution. A Spanish, Portuguese or even a Latin American Restaurant is well acquainted with this ceramic and its special treatment and knows how to handle the goods with care. Please observe the following instructions.
- Rinse the bowls carefully before using them for the first time.
- Rub the bowls with plenty of olive oil and heat the unfilled, new bowls to 250°C. In this way you naturally and hygienically reduce the open porosity of the hard ceramics.
- Avoid frequent rinsing with aggressive alkalis. It is best to rinse the ceramics with clear water. When used in the oven, many residues practically clean themselves. After rinsing, do not stack the dishes. The residual moisture in the open-pored ceramic must dry out with sufficient air circulation. In a bumper shop, you can accelerate the drying process in the pizza oven or in the oven.
- Avoid edge impact; ceramics are considerably more sensitive to impact than porcelain.
- Never stack more than six bowls on top of each other at the mise en place, otherwise the dead weight of the stack can cause damage even to the lower bowls.
- Always serve hot bowls (coming out of the oven) on a porcelain plate (from Holst). It is not only about protecting the guest, but also the furniture and table settings.
- Do not store food in the dishes. Liquids in particular sink quickly into the open-pored ceramic.
- Always give a cooled ceramic dish sufficient time to reach normal room temperature before placing it in the oven. Otherwise, the ceramic dish will crack due to thermal shock.
- With the necessary care and proper maintenance, ceramic bowls, like porcelain, have a virtually unlimited lifespan.
The High Terracotta from Holst Porcelain
The essential difference between High Terracotta and normal terracotta is the composition of the raw materials and a higher firing temperature. In combination, both components result in a higher thermal and physical stability of the product and thus better usage properties. In contrast to classic terracotta, the material is “dense”, i.e. it no longer absorbs liquids and thus has a higher, more audible sound. The edge impact strength increases from 0.04 to an average of 0.15 joules, illustrating the approximately four times higher material stability compared to conventional terracotta. All items in “High Terracotta” grade are produced in a double-firing process. The bisque firing, which lasts about 5.5 hours, reaches maximum temperatures of 1,050 °C and dries out the body completely. The special character of this grade is created by the admixture of hardening, mineral additives and the use of pre-fired fireclay powder, which are added to the clay. What these consist of in detail is a company secret.
Glazed High Terracotta receives the glaze firing with maximum temperatures of 1,090 °C for a further 4 hours. Only high quality clay feldspar glazes are used, which are primarily designed for use as food contact items. Manufacturers of ice cream and convenience products even use High Terracotta vessels for ready-to-serve finished products that are stored and transported in the supply chain chilled down to minus 29 °C.
High Terracotta has a much higher thermal load capacity and can be heated up to 350 °C in a pizza oven, gas oven or Cobi-Steamer and even exposed to open flame.
High Terracotta ceramics are considerably cheaper than porcelain and similar to porcelain in their specific usage properties. In the ovenware segment in particular, High Terracotta offers comparable usage properties to porcelain with lower energy requirements and a lower price. High Terracotta is particularly suitable as
- Casseroles and casserole dishes
- Baking dishes and ramequins
- Serving dishes for gratinating
- Fire pots
- Lanterns and oil lamps