Thin Sections

Analyses of thin sections using Polarising microscope is a well known geological method. A craft oriented analysis of ceramic thin sections adds considerably to results gained through a normal mineralogical analysis. Observing the grain size distribution and the composition of the larger grains, it is possible to discern added temper. In this way the mineralogy and coarseness of the original clay and the amount and grain size of the added temper may be analysed separately. This leads to important information on the raw material choices within the pottery craft.

bronsalder

Thin-section of granite-tempered pottery from the Bronze Age.

medeltid

Thin-section of sand-tempered and wheel-thrown Medieval pottery.

At KFL we register as a routine the relative amount of silt and sand in the clay, its richness in iron oxide and mica,and its content of dark minerals, ore and other mineral grains. In addition the registration of diatoms and calciferous fossils has proven to be of great value in determining the origin of raw clays. Further on the type or types of temper is determined, the amount calculated and the mean max grain size measured. In some cases it is possible to observe structures in the ware which reveal the building techniques used. The existence of slip on the surface may furthermore be verified in the thin section.

Measurements and calculations are performed on the coarse fractions by means of image analysing equipment consisting of a 3-chip colour video camera connected to a frame grabber in a computer. The software used for the image processing and analysis is KONTRON KS 300. The software offers interactive measurements and the possibility of automating repetitive measurements according to pre-set requirements.

Picture analysis at the computer

Traces of use are encountered regularly and may be particularly interesting in the analysis of moulds, crucibles and other technical ceramics.

 

 


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