In the area of pottery analysis by neutron activation analysis (NAA), the number of sample preparation procedures, prior to chemical analysis, appears to be directly proportional to the number of different laboratories involved. This paper outlines the results of heating (a) excavated and (b) surface sherds of Halaf ware from the Khabur Valley. It was found that both sets of samples lost the same relative amount of weight. X-ray diffraction and microscopic analysis showed that the weight loss was due to the decomposition of carbonates. The nature of this process and its impact on the validity of the analytical results -- in terms of major and of trace elements -- is discussed. -- AATA