Discovering the hidden history in pottery shards

Posted on March 24, 2015

The ceramics industry, which is still thriving today, came into being when humans discovered that they could form clay mixed with water into objects that could then be made more durable by subjecting them to heat. Archaeologists now know that humans have been making animal and human figurines from clay and other materials, and firing them in kilns that were partially dug into the ground from as early as 24000 BC, and that pottery vessels were used as far back as 9000 or 10000 BC for storing water and food.

The University of Pretoria (UP) is home to one of the largest ceramic collections in South Africa. The collection contains ceramic objects from the Near East, European ceramics from the Netherlands, Germany, France and the United Kingdom, as well as many contemporary ceramic objects produced in South Africa and other African countries. The best-known of these collections is the University’s Mapungubwe collection, which comprises a museum collection consisting of large number of cultural and heritage objects associated with Mapungubwe and a research collection that includes a vast number of complete or partially complete ceramic vessels and shards. The museum collection is exhibited and curated by the Department of Museums and Arts Management and the research collection is managed by the Department of Archaeology.

The majority of the artefacts that form part of the University’s Mapungubwe collection were excavated at Mapungubwe, a UNESCO World Heritage Site in the Limpopo valley. Archaeologists have been piecing together the history of the mysterious Kingdom of Mapungubwe for decades and have found that the civilisation that existed there extended from around AD 1020 to AD 1290, in other words, during about the same time as the Middle Ages in Europe. Researchers have established that the part of the site known as Mapungubwe Hill, was once the capital of a country as large as Swaziland surrounded by more than 200 satellite towns and that the royal court at Mapungubwe welcomed traders and people of influence from as far afield as Arabia and the Far East.

In order to make the most of the research opportunities offered by the vast collection of objects contained in the Mapungubwe collection (and specifically the research collection), the Faculty of Humanities recently launched a new faculty research theme (FRT) called ‘Ceramics and related collections’, which is headed by Professor Innocent Pikirayi, Head of the Department of Anthropology and Archaeology at UP. Prof Pikirayi hopes to rebuild the history and gain a better understanding of the peoples of southern Africa by analysing elements of this extensive pottery collection in a new state-of-the-art, specialist ceramics laboratory on the University’s South Campus.

Since pottery has, since the earliest times, been commonly used during the course of daily human activities such as the preparation and storage of food, pots in various stages of fragmentation are among the finds most commonly uncovered during archaeological excavations. These remains of material cultures are what archaeologists often study and refer to when trying to interpret and understand past societies. A further aim of the study of ceramics, also known as ceramology, is to reach beyond the physical ceramic object in an attempt to gain an understanding of the activities that characterised ancient societies in order to create a form of contact with prehistoric man.

One of the new ‘toys’ acquired by the University for the Department of Anthropology and Archaeology’s new laboratory is a hand-held X-ray fluorescence (XRF) spectrometer, which is an X-ray instrument commonly used for the routine, relatively non-destructive chemical analysis of rocks, minerals and sediments. The ease and low cost of sample preparation, combined with the stability and ease of use of the device, makes it ideal for the analysis of both major and trace elements in ceramic materials. This laboratory will also give researchers access to a variety of other state-of-the-art equipment, such as a petrographic microscope, which is a type of optical microscope normally used in optical mineralogy to identify rocks and minerals in thin sections.

A thin section is a laboratory preparation of a pottery shard, bone, rock or mineral sample for use with a polarising petrographic microscope, an electron microscope or an electron microprobe. A sample is prepared by cutting a thin sliver of material from the object or shard and grinding it optically flat. It is then mounted on a glass slide and ground smooth by using progressively finer abrasive grit until the sample is only 30 μm thick. This allows for the analysis of a previously unexposed side of the ceramic material, rather than running the risk of only analysing the material on the outer layer of the object, which could have been contaminated by the soil in which it was embedded for thousands of years. Although it sounds somewhat destructive, this method is ideal for use in ceramology as ceramic shards are normally quite plentiful and the size of the sample needed for analysis is miniscule (only 1–3 mm).

The aim of analysing the trace elements of ceramic materials in this way is to determine which raw materials and techniques were used in the production of the object. The trace elements identified in the process can also provide valuable clues as to the possible use of the object. Furthermore, the chemical data, in combination with a study of the vessel shape and decorative elements, can provide answers to questions about the distribution of prehistoric Iron Age ceramic materials. By combining the results of several independent analyses, it is possible to gain information on different handcraft traditions and about contact and relationships among different groups of people.

A great example of how information obtained through analysis can shed light on the activities of the inhabitants of Mapungubwe are the few fragments of Chinese celadon found on Mapungubwe Hill. These fragments are the only imported ceramics found at this site. Celadon originated in China and later spread to other regions in Asia, such as Japan, Korea and Thailand, which means that people from those countries – or at the least people who had contact with them – must have visited Mapungubwe at some time in the distant past. Celadon shards, with their characteristic glaze and colouring, are rare and valuable clues to international trade and have also been found at Great Zimbabwe and the many ancient trading ports along the east coast of Africa.

Professor Anders Lindahl, a professor in Laboratory and Experimental Archaeology at Lund University in Sweden, has been collaborating on research projects at UP for a number of years and is an international collaborator on the new FRT. His involvement with this FRT will include the training of personnel and students in both South Africa and Sweden in the handling of laboratory instruments and data processing. 

- Author Ansa Heyl

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