Terracotta processing

Phase 01

Extraction

The processing of terracotta artifacts begins from the quarry, usually located next to the furnace for obvious practical reasons, where the clay is extracted in the summer, when the earth is drier. The earth, before being ground, is left to dry outside and then stored under a loggia. Contrary to other clays - already pure, or almost pure, in nature - the imprunetine galestro is rich in coarse and stony parts that must be eliminated to obtain a high quality product with good weather resistance.

Phase 02

Grinding

Once stored in the loggia, the earth undergoes a further selection of the stone as it emerges to the surface, thus the earth that will go inside the mill will have less impurities. The elimination of the stone is essential to obtain a high quality product with excellent weather resistance. The grinding is done by means of a hammer mill, these rotate at very high speed, crushing the earth which, through a grid that acts as a sieve, passes subsequently into the containment chamber.

Phase 03

Kneading

Once the earth has been ground and reduced to a powder, it is mixed with water, in different percentages depending on its use - which we will see in the processing techniques - by means of a mixer which, using a rotating arm, mixes the water with the earth.

terracotta production - ancient Mariani Mital furnace - Impruneta

Phase 04

Realisation

The creation phase of the artifacts takes place through various traditional techniques passed down for generations. "Posteggiatura" is the oldest technique, performed entirely by hand without the aid of casts; "A Guscio" processing involves the use of an internal mold on which the clay is pressed; finally, the "A Calco" technique uses modular plaster molds to faithfully reproduce decorations and shapes in negative.

Phase 05

Drying

The necessary drying phase before firing in the oven requires a very variable time depending on the season and the weather, and for some artifacts it can even reach two months. It is an indispensable process given that an earlier cooking than drying can cause the terracotta to break. During drying, the dark gray color of the artifact determined by the water becomes lighter. This process must be gradual to avoid deformations or cracks that can occur in the case of too early exposure to direct light and the heat of the sun.

Phase 06

Cooking

The cooking process, which now takes place with the gas-fired oven, was previously carried out in the Roman oven, fueled by wood. This process lasts about 60 hours. The maximum temperature peak is 1000 degrees, these must be reached gradually, as well as the descent, any thermal shock would compromise the artifacts inside the kiln.

Phase 07

Wetting

The process following cooking is wetting, once the products have been removed from the oven, already at a low temperature, they are placed outside and wetted with water. This process is essential to prevent terracotta artifacts from starting an internal fermentation process, which would lead to the object crumbling over time.

Phase 1

Extraction

Phase 2

Grinding

Phase 3

Kneading

Phase 4

Realisation

Phase 5

Drying

Phase 6

Cooking

Phase 7

Wetting

[ Processing ]

The Posteggiatura

The oldest of the processing techniques

Posteggiatura is the oldest of the techniques and is done entirely by hand, without the aid of any shape or mold. It is also the most difficult technique, being entirely entrusted to the skill and experience of the craftsman. Before starting, a drawing is made that reproduces the features of the vase and the relative measurements, taking into account the fact that the material, when drying, is reduced from 8% to 10%. The processing starts from a support surface, in terracotta or wood, on which the “foundation”, or the base of the object, is created by using a “hub” of earth, that is a clay ball, which is flattened with the hands to give it a circular direction, and leaving it a little raised at the sides so as to be able to attach the “wick” well: the clay, in fact, before being used, must be spread on a surface and given a elongated shape, like a long stick (or “worm”), called “wick”.

posteggiatura processing terrecotte Impruneta

[ Processing ]

By Shell

The artifact is made with the help of a shape

In the shell processing the artifact is made with the aid of a form, once in terracotta, today mostly in plaster, which is sprinkled with earthenware powder to prevent the clay … to stick. The clay is pressed from the outside following the methods of the previous technique, or by “parking” the wick around the form. The element remains stationary while the person, proceeding backwards, turns around pressing the clay on the shape itself. Once this phase is finished, the vase is immediately turned upside down on a support surface, then the shape is extracted.

[ Processing ]

In Cast or Mold

Cast or mold processing has been used in more recent times

Cast or mold processing has been used extensively in more recent times, between the end of the nineteenth century and the beginning of the twentieth century. It uses modular molds in terracotta, or more commonly in plaster, inside which the clay is manually pressed, in order to reproduce the shape of the product “in negative”. When the clay has partially dried, the walls of the external shape, generally equipped with festoons or decorations of different types, are removed, leaving the vase already defined in all its decorations and shapes. At this point the object is smoothed and finished in all its details.