Radiocarbon dating of lime lumps: current and future challenges

This paper discusses some of the main differences between the radiocarbon mortar dating technique based on the use of lumps of pure lime, and the technique based on the use of bulk mortar samples. The paper also discusses the main limitations of the current application and development of the lime lump technique, mainly related to the limited knowledge currently available of the chemical, physical, mineralogical and isotopic composition of the lumps. These limitations are supposed to be the reason why, despite the successful results obtained over the last 20 year, the lime limps technique is not yet widely used in archaeological excavation and conservation works. The paper aim at contributing to the debate on the development of the mortar dating techniques and, in the conclusions, suggests that the technique based on the lime lumps should not be considered as a substitute of the technique based on bulk mortar sample (as suggested in a recent publication) but, on the contrary, as an alternative technique. This approach will provide archaeologists and conservators with a richer and more useful toolbox for mortar dating, suitable to every circumstance.