Raising the temper - μ-spot analysis of temper inclusions in experimental ceramics

Provenancing of ancient ceramics is a highly important scientific tool for archaeological studies. In general, ceramics are not made from the original clay, as it can be found in deposits. To produce the needed physical properties in the finished product, the clay has to be either tempered by adding sands or biological materials or levigated, to remove the coarse fraction. Thus, the chemical composition of the finished ceramic differs from the composition of the original clay bed. To overcome this obfuscation, any information that can be gained about the temper used is useful. In a small series, several pieces of ceramic were produced from known clay and tempers and the resulting ceramics analysed by INAA. As many attempts to physically separate the temper from the clay matrix have failed, μ-spot analysis of temper inclusions were performed at the μ-PIXE (Particle induced X-Ray Emission) facility in Rossendorf and by LA-ICPMS (Laser ablation Inductively coupled plasma mass spectroscopy) in Aberystwyth. It could be shown that from a small number of measurements, a general impression of the temper used could be gained, showing if the temper consists mainly of quartz, feldspars or other main components. With this information, dilution calculations can be greatly facilitated, and a close resemblance of the chemical composition of the clay matrix can be calculated.