Experiments on the effects of carbonization on some cultivated plant seeds

Abstract

Seeds and fruits of plants have different chances of getting carbonized in archaeological contexts. This chance depends on the one hand on the use of each plant; some plants are more likely to get in contact with fire than others, for example when they have to be roasted or cooked before eating. On the other hand this also depends upon the consistency and texture of the seeds themselves, which carbonize under different circumstances. The aim of our experiments was to reveal systematically the behavior of Setaria italica, Panicum miliaceum, Papaver somniferum, Linum usitatissimum and Cannabis sativa during carbonization. For this purpose we heated seeds of each species under both reducing and oxidizing conditions for 1–4 h in a muffle furnace to temperatures of 180–750°C. The results were striking: while reducing conditions usually enlarge the temperature range at which seeds carbonize without getting destroyed, broomcorn millet behaves exactly the opposite way. Papaver somniferum has only very little chance of becoming carbonized at all, because the temperature range at which this happens is very small. The chances of carbonization for Linum usitatissimum are quite good, those of Cannabis sativa even better.