The precision of porosity measurements: Effects of sample pre-treatment on porosity measurements of modern and archaeological bone

Bone porosity plays an important role in the taphonomic trajectory of bones. Porosity analysis of archaeological material can indicate diagenetic events in the bones taphonomic history. Furthermore, measuring the porosity of modern bone material can potentially provide a method for assessing the relative likelihood of survival for different skeletal elements. Here we critically assess the use of nitrogen adsorption porosimetry and mercury intrusion porosimetry for analysing porosity of a range of bone preservation types; from modern fresh material to highly degraded archaeological material. In addition a number of sample preparation methods were assessed. Our results indicate that bone porosity measurements show large variation, which may limit their usefulness when analysing modern material. Features observed in pore size distribution graphs are, however, consistent and thus this data would appear to be a useful indicator of diagenetic processes that have occurred in the bone. The most effective method for preparation of the bone is lyophilisation which renders the bone dry enough for analysis and does not appear to cause a visible systematic error in the measurements.