ÇATALHÖYÜK 1997 ARCHIVE REPORT

1997 REPORT ON EXPERIMENTAL ARCHAEOLOGY AT ÇATAL : Manufacturing Bricks for the House Replica

Mirjana Stevanovic´

Thanks to the generous support provided by MEPTUR organized through the Turkish Friends of Çatalhöyük during the month of September 7-14, 1997 phase one of the Neolithic House Replica Project was carried out at Çatalhöyük.

The aims of this phase of the project were:

(i) to locate the most adequate sources of the building materials that can be used for the Neolithic house replica;

(ii) to make several soil mixtures - recipes - which can be used for the bricks;

(iii) to build the molds and manufacture the bricks

(iv) to carry out a controlled experimentation;

(v) to store the bricks during the winter.

The participants in the Project were in addition to myself, Ismet Ozkut, a local brick maker from Çumra, Hulusi, Ahmed and Ahmed, and Khalil from the local village of Kücüköy, who worked on acquisition of the raw materials and as Ismet's assistants. All the stages of this project phase were carefully monitored and recorded.

In this phase of the project I decided to concentrate on identifying and experimenting with raw materials for bricks.

According to the findings of the micromorphological researches at ÇH in previous years the source materials for bricks were silt loam and sandy silt loam sediments with finely fragmented plant remains and burnt aggregates, and in the later levels they comprise alluvial and alluvial fan deposits. Many of the bricks were made from natural sediments exploited from the surrounding region, and stabilized with vegetal remains.

The geomorphological and geoarchaeological study of the vicinity of the Neolithic site in the previous years shows that Çatalhöyük is likely to have been located at the southern edge of an extensive marsh or shallow lake during the terminal Pleistocen. Thus the ground surface soil in the Neolithic times was likely to have been backswamp soil. It comprises heavy, dark greyish brown (2.5Y 3/2) clay, which presently lays buried under the thick layer of upper alluvium.

My research proceeded on the assumption that it is very likely that the ground soil was used as building material in the Neolithic considering the quantities of soil necessary for large number of bricks and possibly for roofs, and considering the properties of clay which was deposited in the backswamp environment for construction.

I conducted the Gravity Separation Test on three samples of the Neolithic bricks from the site and in the same time on variety of other soils that are locally available and I was able to get them from a palaeochannel section south of the archaeological site. These are: soil from the upper alluvium layer, backswamp soil that represents lower alluvium, organic clay that lays under the backswamp soil and a sample of marl soil which lays under it. The results of the test indicated that by far the greatest similarity exists between the backswamp soil and the soil that the Neolithic bricks were made from. Even without this test it seemed that the backswamp soil had the best characteristics as building material (proportions of clay, sand and organic materials). Thus, I chose this soil to be used as basic soil for the bricks to be manufactured.

It is apparent at Çatalhöyük that variety of soils were used as building materials throughout the long history of the Neolithic settlement. At this point of research it is impossible to identify all these materials. The aim of this phase of the House Replica Project was to identify what seems to be the most commonly used building material. The backswamp soil was designated as such material. This is a heavy silt-clay that is notably lacking a coarse fraction, and can have organic values >5%, suggesting deposition in the 'backswamp' environment of flood basins.

However, in order to introduce another variable in the brick manufacture experiment I decided to use in addition to backswamp soil one more type of soil, the very soil that comes from the Neolithic site itself. That is the slack-soil from flotation which represents the mixture of soils from the Neolithic site. This soil gets deposited in the pit nearby the flotation tanks as the result of flotation routine. The flotation soil is quite sandy partially because it was lacking plant material that was separated in the process of flotation but also because large quantities of this soil come from the excavation units in the Bach and North areas of the site. These areas seem to feature bricks which were made of alluvial deposits with medium to coarse sandy clay loam.

Raw Materials used in my brick manufacture were:

… backswamp soil/Neolithic ground soil

… sandy clay loam from the Neolithic settlement that has been collected as a slack in the process of flotation

… mixture of these two soils

… vegetal materials, that is, straw and chaff mixture that can be found in the local villages, which is prepared for contemporary building activities as well as for fodder.

Labour Expenditure in gathering Raw Materials:

In one instance three workmen invested 15 hours of work and they were able to dig out 0.802m3 of backswamp soil. They used spades and picks. Thus in one working day the three of them supplied almost one Tone of soil. The transportation of this soil to the site took 2.5 hours using a car. Acquisition of vegetal temper took 1 hour and one person. Water supply is difficult to measure.

Brick manufacture:

Total number of manufactured bricks in this season is 272. Sixtyeight bricks were in size 120x30x8cm; 68 bricks were 60x60x8cm; and 136 bricks were in size 30x30x8 cm.

Brick sizes at Çatalhöyük vary considerably. In the newly cleaned and excavated sections at Çatalhöyük we have some control of brick sizes that were used in the Neolithic. However, our sample is not large enough to show if there were standardized sizes of bricks in the Neolithic. In order to account for the most common brick sizes at Çatal I decided to manufacture my bricks in the three sizes that are described above. In the future experimentation (mainly in 1998) some brick-replicas will be made in exceptionally large sizes (close to 2m in length).

Five piles of soil mix were created in the course of the brick manufacture. They differ in the soil type and quantity of vegetal material that was added.

Soil mix #1: 36% of flotation soil, 64% of backswamp soil. In this soil mixture straw/chaff component was 16% and 84% was soil.

Soil mix #2: 30% of flotation soil and 70% of backswamp soil. Chaff and straw component was 10% and soil 90%.

Soil mix #3: 100% backswamp soil. In it the vegetal component was 16% and 84% was soil.

Soil mix #4: This soil mixture contained 14% of vegetal material and 86% of backswamp soil.

Soil mix #5: 16% was made up of vegetal materials and 84% of backswamp soil.

Drying time: In a very warm and dry conditions it takes from 7 to 15 days for the bricks to dry. Once dried the bricks were very hard and compact. Ismet demonstrated this by dropping a medium size brick from ca. 70cm on the ground and the brick did not fall apart. Also, transporting dry bricks from the area of manufacture to the storage are was not a problem at all. This experiment shows that bricks that are up to 120 cm long did not need to be moulded in situ on the walls. Future experiments will show if this was the case with larger bricks as well.

Brick Marking: I decided to mark the bricks by making an impression in them while they were wet in order to recognize later which bricks come from what soil mix (soil mix 1-5).

0 = bricks made of soil pile 1

X = " " 2

III = " " 3

XX= " " 4

no marks= " 5

Sampling Strategy:

Archive samples were taken from the five soil mixture piles. That is, 2 kg. of soil mixture was taken in a sample for the future reference and analysis. These samples remain for now packed in the dig house at Çatalhöyük. One brick sample, cut out of a finished brick I gave to Wendy Matthews for micromorphological analysis. One brick sample from the same brick was taken by me and was shipped to Philadelphia for analysis.

Experimentation:

In addition to manufacturing the bricks, an experimental test was carried out to see how would bricks made without addition of vegetal material hold. In this experiment I used three groups of soils: backswamp, flotation soil and the mixture (1/2&1/2) of the two. There were three groups of bricks made, each including 2 large brick, 2 medium and 2 small bricks. Changes on these bricks during the process of drying were carefully monitored and recorded.

The concluding remarks on the experimental bricks: all the bricks, but one developed cracks and in most instances the cracks were fatal for those bricks. The only brick that did not crack is a small size (30x30x8 cm) and made of flotation/sandy soil. This experiment indicates that backswamp soil or the flotation soil or their mixture if used for brick manufacture without vegetal material produces unsuccessful bricks.

Conclusions:

It is very obvious after the brick manufacture that the brick size, shape and surfaces change in the process of drying. Bricks size changes when they shrink and crack; their shape changes by curving of the brick; and brick surfaces develop impressions that indicate types of other materials that the bricks come in contact with as they dry. The relevance of impressions or irregularities in the bricks if spoted on the Neolithic samples can be great for the Neolithic architecture. They can indicate the environment/the ground on which the bricks were made and dried, and the length of time that they spent in such a place. Also, they could indicate if bricks or mortars were wet when brought in contact during building of a wall.