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Taking a Closer Look at the Past: the Microanalysis of Ceramic Artifacts in Archaeology Today

March 12, 2014 1:23 pm by: Kaitlynn

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By: Kamal Badreshany, University of Durham

Petrographic microscopes and stereoscopes. All photos courtesy Kamal Badreshany.

Petrographic microscopes and stereoscopes. All photos courtesy Kamal Badreshany.

When you walk across almost any Near Eastern tell pottery sherds are likely to crunch under your feet. The enormous amount of pottery found on archaeological sites in the Near East is the result of two factors. First is the rapid spread of pottery technology throughout the Near East after its introduction some time around 7000 BC. Second is the inorganic composition of pottery. Since pottery containers are not made of organic materials, such as wood or reeds, they survive over long periods of time and in a wide variety of climates without decomposing or significantly altering. Ceramics are therefore an incredibly important resource for archaeologists trying to gain a better understanding of ancient societies.

Ceramics are best known as one of the fundamental tools for establishing chronology but they have also been used by Near Eastern archaeologists, sometimes controversially, to make a variety of social, cultural, and economic inferences about ancient peoples. This is akin to trying to reconstruct a modern person’s social, ethnic, or national identity using items commonly found in their kitchen like mugs, dishes, Tupperware, or other items used for the preparation, consumption, and storage of food.

Hexagonal quartz grain in thin-section (center of image).

Hexagonal quartz grain in thin-section (center of image).

How do archaeologist extract important social and economic information from these quotidian objects and what are the limitations regarding what they reveal about ancient peoples?

Analyses begin in the visible world. For one thing archaeologists examine the different attributes of a ceramic objects to better understand what they were used for. The presence of a spout, for example, means pouring and can indicate a vessel was used for storing or consuming liquids. Burning or traces of soot on the outer surface of a vessel commonly indicate cooking pots or lamps. The analysis of the macroscopic features can even inform about belief or artistic influences. Fine craftsmanship, symbolism, or complicated production techniques may identify some vessels as high status or important ritual objects.

Light microscope image of a ceramic thin-section magnified 15x. The angular fragments are mostly composed of the mineral olivine. Chalcolithic Pottery, Syria

Light microscope image of a ceramic thin-section magnified 15x. The angular fragments are mostly composed of the mineral olivine. Chalcolithic Pottery, Syria

One of the main goals of ceramic analysis is to better understand ancient societies by recreating activities that took place in rooms and buildings found during excavations and how these change over time. The distribution of vessels used for cooking, eating and drinking, storage and other tasks may tell archaeologists about the organization of those activities.

Overall, the macroscopic attributes of ceramic objects yield a great deal of information for the archaeologist, but far more can be gained by studying the ceramic materials directly.

Scanning electron microscope image showing a basalt fragment magnified 250x. Neolithic Pottery, Syria.

Scanning electron microscope image showing a basalt fragment magnified 250x. Neolithic Pottery, Syria.

Archaeological science (sometimes known as archaeometry), uses scientific techniques to investigate directly the materials from which ancient objects are made. An archaeological scientist studying ancient ceramics would aim to analyze the atomic or molecular composition of the clays and other materials that the vessels are made from. This analysis is usually conducted by using complicated (and expensive!) pieces of analytical equipment such as light and scanning electron microscopes, spectrometers, diffractometers, and chromatographs – to name a few of the most common. Most instruments measure the interaction of matter with light over specific portions of the electromagnetic spectrum like visible light, X-ray, and infrared radiation. Each technique and instrument has advantages and disadvantages. As is often the case, the correct technique and machine depends on the research question or questions.

Point Energy Dispersive X-ray Spectrum of Naturally Occurring Titanium Oxide Grain in a ceramic Sample.

Point Energy Dispersive X-ray Spectrum of Naturally Occurring Titanium Oxide Grain in a ceramic Sample.

Archaeologists studying ceramic materials at large research institutions often have a variety of techniques and instruments at their disposal. The most commonly used can be divided broadly into two groups. The first, ceramic petrography, looks directly at the minerals, rocks, voids, and their relationships to other microscopic textural features in a ceramic sample. The objects in the sample can be identified because their properties, related to interaction with light being transmitted through them at a certain thickness, are known. This ‘thickness,’ known as ‘optimal thickness,’ is exactly 30 microns, and is achieved by slowly grinding and polishing a ceramic sample until what is commonly called a ‘thin-section’ is produced. Thin-sections are commonly analyzed using a light microscope or a scanning electron microscope.

Basalt fragments, probably added as temper.

Basalt fragments, probably added as temper.

The second group of techniques analyzes the bulk chemical composition of materials. Commonly used techniques include neutron activation analysis (NAA), inductively coupled plasma atomic emission or mass spectrometry (ICP-AES and ICP-MS), x-ray fluorescence spectrometry (XRF), x-ray diffraction, and gas chromatography. These instrument platforms provide quantitative bulk elemental or molecular measurements.

The techniques vary in the kinds and amounts of elements they measure effectively. Neutron activation analysis and inductively coupled mass spectrometry can measure the quantity of minor and trace elements found in a sample, like thorium, uranium, and cesium to concentrations on the order of parts per billion. Inductively coupled plasma atomic emission measures commonly occurring elements like silicon, iron, and aluminum. In the most favorable conditions x-ray fluorescence spectrometry can measure major, minor, and trace elements, but with less precision than other technique, on the order of parts per million. X-ray diffraction identifies the different mineral phases (series of different atoms with an ordered structure) in ceramic samples. Gas chromatography (GC) identifies organic compounds, like fats and lipids but is not commonly used to analyze the ceramic materials directly, but rather residues that accrue on their surfaces through use. The technique is useful for identifying the contents held in ceramic vessels in the past and has been used to identify wine and honey residue in vessels, giving an indication to their function and contents.

Clay full of tiny marine fossils called foraminifera, their presence indicates the clay used for this sample was derived from chalk outcrops.

Clay full of tiny marine fossils called foraminifera, their presence indicates the clay used for this sample was derived from chalk outcrops.

Different kinds of information are gained from petrographic and bulk analysis and the techniques are complementary. Both are concerned with understanding the origin of the ceramic materials in order to identify production centers. Identifying the origins of vessels at various sites then allows for reconstruction of trade between sites and regions. Petrographic analysis yields information about ceramic production and the spread of technology. For example, we can examine the voids and overall grain size in a sample to determine whether a vessel was hand or wheel formed. This is not be possible using bulk chemical methods. The properties of the clay and the minerals found in ceramic samples indicate at what temperature and for how long vessels were fired. The minerals, rocks, and clay pellets in a sample can identify the mixing of clay materials and provides an understanding of why certain materials were selected, indicating the intended use of the finished product. Bulk analysis, on the other hand, serves to reinforce petrographic data and can provide very precise chemical signatures for the clay outcrops where materials used to make a group of ceramics were taken.

El Amarma tablet mentioning Alashiya.

El Amarma tablet mentioning Alashiya.

Putting the information gained from the petrographic and chemical analysis of ceramics together can often allow for reliable, wide ranging, social, political, and economic interpretations of the past, which would not be possible using macroscopic studies alone. These have begun to transform our understand of the past in large and small ways

Petrographic analysis has been used, for example, to help better understand the political landscape of Late Bronze Age through analysis of the Amarna letters. The Amarna letters are Late Bronze Age correspondence written on clay tablets between the Egyptian Pharaoh, his vassals in the Levant, and other great powers. The tablet were found at Tell el-Amarna in Egypt but were sent from all over the Near East. Yuval Goren of Tel Aviv University petrographically analyzed the clay from which the Amarna tablets were formed, working on the assumption that these tablets were made of material available locally to the senders. As a result of these analyses, the geographical location associated with a number of place names previously unidentified discovered. Most importantly, the major Late Bronze Age kingdom of Alashiya, which based on Goren’s petrographic and chemical analyses of the letters sent from there to the Egyptian pharaoh, was convincingly identified as being located on Cyprus.

Phoenician maritime amphora.

Phoenician maritime amphora.

Another study, conducted by Elisabeth Bettles then of University College London, investigated the distribution of different types of Persian Period (539-332 BC) transport amphorae, thought to originate from the Phoenician city of Tyre, using a combination of petrographic and chemical analyses. These amphorae are often thought to have been used to carry goods such as olive oil and wine, many of which were sent throughout the territory of the city-state by a central administration. Her work showed the existence of a highly centralized production system for these vessels, indicating the presence of a centralized redistributive economy during that period. The distribution of these amphorae, covering parts of southern Lebanon and northern Israel accorded well with historical documentation about the extent of the territory of Tyre during the Persian Period, helping to reinforce our understanding of the borders of the city-state during that period.

Archaeological science has contributed a great number of techniques for the analysis of ceramic materials, increasing the ways in which we can understand past societies. Future developments in the field will surely contribute new instruments and techniques, continuing to increase the information that can be retrieved about past societies through the study of ceramic materials.

Kamal Badreshany is Research Associate in the Department of Archaeology at the University of Durham. 

Some other links to check out:
PETRODATABASE

Thin Section Petrography of Ceramic Materials

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Ancient Near East Ancient Near East Today ANE Today Archaeology ASOR Ceramics Kamal Badreshany Microanalysis Near East Near Eastern Archaeology University of Durham
Taking a Closer Look at the Past: the Microanalysis of Ceramic Artifacts in Archaeology Today Reviewed by Kaitlynn on . By: Kamal Badreshany, University of Durham [caption id="attachment_7000" align="alignleft" width="231"] Petrographic microscopes and stereoscopes. All photos co By: Kamal Badreshany, University of Durham [caption id="attachment_7000" align="alignleft" width="231"] Petrographic microscopes and stereoscopes. All photos co Rating: 0
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