Analyses of ceramic materials
Archaeological finds of ceramics amount to a mass material on certain types of sites, in certain periods varying from area to area. On other sites, in other periods and areas, the finds may be few and scattered. All the same, ceramics often make up the only more complex culture historical objects capable of providing knowledge about the site and the activities that once took place there.
Ceramic finds may be divided into “pottery” and “technical ceramics”. The latter term denotes a group of fired clay objects that often fill a function within other crafts. Examples are loom weights, crucibles, casting moulds, perforated cylinders for heating, clay discs and fire dogs. Technical ceramics also appears as parts of constructions such as furnace, kiln and oven walls, clay linings of hearths. Analyses of technical ceramics objects and structural parts utilise the same analytical methods but the basic research questions deal to a higher extent with the function and functionality
Planning of ceramics projects/analytical work in close collaboration with the archaeologist
The most important phase in all analytical work is the project planning. Here, the specific questions to the material are formulated. The questions addressed to the ceramics should not only be appropriate for the overarching research goals for the site, but even be adjusted to the methods of analysis chosen. The detailed planning for the analytical work may ideally take place before the excavation takes place or after the excavation but before the finds processing is started – both solutions with their respective advantages and disadvantages.
SKEA’s more than 15 years experience with this kind of project planning in most cases provides satisfactory results.
Recording of technical traits, vessel reconstructions, dating etc.
Many times a thorough recording of a ceramics material and a subsequent culture historical interpretation of the results may answer the archaeological questions addressed to the finds.
A full scale recording of the main technological traits incorporates observations of temper type and quality (amount, max. grain size), vessel part, surface treatment, firing and traces of use and secondary deposition on every single sherd related to its thickness and weight as the basic statistical parameters. All rim- and base-sherds as well as all decorated sherds are drawn. Rim and base diameters are calculated and used for reconstructions of the original shape of the pot. Reconstructed vessel forms, ornamented sherds and ware descriptions forms the basis for a typological determination and dating.
The different vessel types found within a settlement are discussed in relation to a possible, functional household inventory. The spread of the sherds and their state of preservation reflect the organization of different activity areas and the level of activity. This model recording is always adjusted to suit the needs of any specific investigation in a cost effective way.
The recording of technical ceramics concerns the raw materials, their mixture and homogenization and the shaping of the objects/construction elements. The use effects are often more important factors to record on technical ceramics than on pottery – especially for those objects which have been involved in processes using heat. As an example, the differential stepwise firing of furnace walls from the inside exposed to the iron reduction process outwards towards the barely heated outside as well as the degree of reduction of the ware from the inside out, make up an important source of knowledge about the function of the furnace. Repairs of furnace walls, crucibles and other technical ceramics tell about curation as an important factor in the crafts.
It is very important to choose appropriate methods of analysis providing substantiated results in a cost-effective way.
SKEA is working according to the same pyramid-organization of analytical techniques, which has been standard at the Ceramics Research Lab for nearly three decades. The pyramid organizes the work effort in relation to the size of the sample and divides it into a series of levels. The higher up in the pyramid the analytical work progresses, the more precise the scientific questions will have to be in order to obtain valid and useable answers. For each analytical step that has been executed, the results must be evaluated in relation to the original scientific question. This procedure ensures cost effectiveness since the analytical work is not continued beyond what is required to reach satisfactory answers to the problems it set out to solve. Furthermore, the procedure also provides the best possibilities to achieve good results from ensuring more advanced/detailed methods should they be deemed necessary.
Microscopy of thin sections of ceramics – Provides detailed information on raw material choices and ware compositions, building techniques, secondarily intruded materials related to function or deposition
Thermal Analyses – estimating firing temperature and the thermal capabilities of clays and wares.
Chemical Analyses – i.e. P-ED-XRF etc. are mostly used to determine particular inclusions such as metal droplets in crucibles or on special surface treatments.
SKEA has almost 20 years of experience within the field and will continue close collaborations with the Laboratory for Ceramic Research, Lund University; Geoarchaeological Laboratory (National Board of Antiquities) and the Archaeological research Lab., Stockholm University in order to maintain a high scientific level.
SKEA produces detailed reports containing interpreted analytical results with a discussion of their impact on the archaeological questions to the finds and the site. The content is presented to and discussed with the archaeologist before the report is finalized in order to ensure that all questions are answered and no unclear points remain. The format of the report – as a separate technical report on paper/electronically, as an appendix to the site report or as a chapter in a larger publication – may be decided by the contractor.