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Production of Iberian ceramics (Protohistory)

Date: 
Thursday, 12 July, 2012 to Saturday, 23 November, 2013
Responsible: 
Natàlia Alonso (Universitat de Lleida)
Grup de reconstrucció històrica Ibercalafell
Ramon Cardona (Centre d'Estudis Lacetans)
Josep Pou (Centre d'Estudis Lacetans / Ciutadella Ibèrica de Calafell)
Number of Participants / Visitors / Audience: 
20

Introduction
Ibercalafell, one of our associated partners in OpenArch, have been carrying out an experiment related to Iberian ceramics production in Verdú, Catalonia, a town located in the province of Lleida http://goo.gl/maps/luItx in cooperation with the University of Lleida (through Recercaixa), the Centre d’Estudis Lacetans and La Ciutadella Ibèrica de Calafell.
Verdú is a famous place in Catalonia due to its ceramic production tradition. There are still workshops and kilns which preserve all the traditional elements and ceramicists who work keeping the ancient techniques of firing pottery in kilns of Arabic typologies. These type of kilns are an evolution of the ancient Iberian and Roman vertical flue and direct flame kilns.

Main objectives

The experiment aimed to know the production system of the Iberian pottery through all processes starting from the structure where ceramic objects were fired. A reproduction of a big diameter Iberian vertical flue kiln in 1:1 scale was made. The model was the kiln of the Casa Grande de Alcalá de Júcar (3rd Century BC) excavated by S. Broncano and J. Coll (Coll, 1987).

A second goal is to know the internal organisation of an Iberian kiln. It is not easy task to load and unload it and a good achievement ensured a lesser decrease after firing. The correct positioning of the different size vessels into the kiln implies the use of different shape supports with the aim to improve the stability of the raw clay pieces. Loading/unloading only for a side door it makes conditional the working tempos of the craftsman. This is a delicate operation and the experimentation may provide a lot of knowledge about the working process of this Iberian craftsmanship.

A third important step is the lighting and firing of the vessels for hours. The experimentation of this process will provide data about temperatures, temperatures control, kiln stabilization, and it will help to understand the process of ceramic production a the main conditioning element of the Iberian ceramic styles, the firing of different size pieces, the reduction and oxidation processes in Iberian times.

Construction of the kiln

The construction of the experimental kiln in Verdú started in 2007 based on archaeological evidences although it has been speculated in relation to the cover. It was also experimented with the materials and the preparation: straw, clay, adobe (sun-dried bricks made of clay and straw).

In 2007-2012 phase, the construction of the combustion chamber takes place. A circular ditch (diameter: 3,50m / height: 1,80m) is excavated. The construction of the perimeter wall is made with 236 adobes (size: 48 x 24 x 9). For the construction of the central pillar, 176 adobes (size: 30 x 15 x 9) were used. The size of these smaller adobes was the same as those in the excavation of the original kiln of the Casa Grande. The adobes were made with clay from the close town of Arbeca and mixed with straw (approximate mixing ratio: 20-25%). Adobes were tested to prove the resistance to high temperatures. They were cooked progressively from 30ºC and 120ºC to eliminate the hygroscopic water first, then to 450ºC to eliminate the structural water and finally to 1060ºC. The result was positive as the pieces resisted the high temperatures.

The most complicated part was the construction of the grill and nozzles. The original kiln had 53 of them.

In the later phase (2012-2014), it is considered to build the firing chamber (laboratory) taking into account the lack of archaeological data from the excavation. At this stage, the experiment has an added difficulty because until this phase the kiln was made based on a well preserved original kiln. The upper level work line starts from a hypothetical approach regarding the shape and the cover as there are only few centimetres preserved of the original kiln upper level.

For the firing chamber construction, 920 adobes would be used. An engineering study was made previously regarding the laboratory shape. Several theories of interpretation were considered. An architectonic study was ordered with the aim to consider the possibility to build the upper level using the false cupola system, done with the approaching of adobe rows.

Before proceeding with the firing of the kiln, the praefurnium and the plastering of the kiln were also made. In July 12, 2012 the kiln is fired, the door is closed with adobes and four sensors are installed. The datalogger station controlling the devices will get information. The firing starts at 9:00AM and, after 18 hours, it stops at 3:10AM.

In July 21, the structure is revised. The pyrometric results show a maximum temperature peak of 600ºC.

Ceramics reproduction

After the success of the kiln firing, it is proceeded to order 160 Iberian pieces of ceramics using a potter’s wheel. Mr Magí Sambola, a local and experienced craftsman, will be in charge to produce them to fill the kiln. At this stage is when the participation of La Ciutadella Ibèrica starts.

A wide range of vessels are in the proposal, preferably bigger size are needed (amphorae, kalathos, etc). A crucial issue is the positioning of the vessels into the kiln, a 3D software will be used to have an approach about how to put the pieces into the kiln.

Early 2013, Mr Sambola works in the elaboration of the vessels. In January 7, the staff of La Ciutadella went to Verdú to see the works on the spot, learning from the craftman how the pieces were being made in his workshop and a visit to the kiln. In September 2013, the archaeologists of Ibercalafell and the Centre d’Estudis Lacetans prepare and repair the kiln for the firing. In October 19, the kiln was successfully loaded. In October 27, the kiln’s door was closed with adobes and sensors to get temperature data were put in different sections of the kiln. The cooking of the ceramics lasted 18 hours. In November 23rd, the kiln was open and we could check the pieces were successfully cooked. Most of them can be seen in the houses of La Ciutadella for the public and all the experiment process has provided a lot of information that we can use as well in the dialogue with visitors.

Images

Ciutadella Ibèrica staff visiting craftman's...
Photo of the pieces during the cooking...
Opening of the kiln with the vessels cooked