There are many terms in the ceramic material context that we need to clarify. Ceramic (from the ancient Greek "Kéramos" which means clay) defines an inorganic,
nonmetallic material, malleable in natural state, stiff after firing.
Usually it is composed by different materials: clays, feldspars (sodium feldspars, potassium feldspars or both), silica sand, iron oxides, alumina, quartz. Such an articulated
mix determines the presence of flattened molecular structures, called phyllosilicates. Their shape, in the presence of water, gives the clay some plasticity and makes
processing easier and more successful.
Over time the term "ceramic" has taken different connotations, depending on different geographical areas. The various kinds of ceramic are used for manufacturing amphoras
and wine vessels.
To clarify the differences among the ceramic materials' types, here are each one's features in relation to their oenological usage:
THE BAKED CLAY: typically brownish red, firing changes from 960° (1760 °F) to 1040° (1904°F). Traditionally it is used for paving and pottery. It is the material used for the most widespread jars, jugs and amphoras (Georgia, Spain, Central Italy) applied in the oenological processes.
ADVANTAGES: very malleable in production, low cost, low firing temperature (lowering the costs of energy).
DISVANTAGES: high porosity, which results in remarkable oxygen permeability and related oxidation of the content. Besides, the porosity causes deep contamination, making cleaning and sanitizing much harder.
THE STONEWARE: it is used mostly to produce bathroom and kitchen tiles and is characterized by firing temperature between 1200° (2192°F) and 1350° (2462°F). The main feature is that there is practically non-existent porosity. Artificial mixture containing white burning clays and quartz-feldspar rocks, which allow the vitrification, are used to get white stoneware. This material has been used in recent years to create oenological vessels.
ADVANTAGES: very high physical endurance, automated processing and easiness of cleaning and sanitizing.
DISVANTAGES: the little porosity allows a very low oxydoreduction (essentially insignificant). The values are reduced by 80%-90% comparing to oxydoreduction permitted in wooden barrels.
THE PORCELAIN: invented in China around the VIII Century, it is made with kaolin, silica (or quartz sand) and feldspar. The kaolin sometimes gives plastic properties and the typical white porcelain color; the quartz is the inert component, exercising a degreasing function (moreover it allows the vitrification); finally the feldspar which is called fondant because, melting at lower temperatures than kaolin, reduces the ceramic mixture firing temperature (1280°C, 2336°F). There are different kinds of porcelain, typical of a given production's area.
THE PORCELAIN IS HARDLY EVER USED TO CREATE OENOLOGICAL VESSELS, DUE TO ITS GLASS-LIKE FEATURES.
THE CLAY: clay's firing temperature depends on the alumina's quantity contained in it. The clay is naturally very malleable, because the water in its structure improves its plastic features and turns it into a material very simple to work with, even by hand. When it is dry, but it has not yet been fired, it becomes rigid and fragile. When it is exposed to an intense heat, it becomes permanently solid.
TAVA'S AMPHORAS CERAMIC MIXTURE
The material used for TAVA's amphoras is the result of close synergies between oenologists, wine producers and technicians specialized in the production of ceramic mixtures.
This close cooperation in looking for materials best tailored to the demands of the winemakers, has made it possible, after years of field testing, to develop a particular mix among the main ceramic products, which is in compliance with the requirements of the oenological world and allows to eliminate those problems that have been the cause of the scarce popularity of ceramic vessels in the wine industry.
The specific characteristics of the ceramic mixture used for TAVA's amphoras are:
TAVA amphoras are fired at a very high temperature from 1200°C (2192 °F) to 1260° (2300°F). This allows the ceramic to be able to get an oxygen permeability that varies from levels slightly lower than those of wood to a total absence of oxydoreduction.
SANITAZING AND CLEANING EASINESS:
Thanks to specific porosity levels, the contamination of the liquid inside the ceramic is superficial, permitting a great ease in cleaning and sanitizing.
THERMAL INSULATION HIGH CAPACITY:
Ceramic's thermal insulation properties are superior to those of cement, allowing an ideal insulation of the content.