Today we had an experimental session at the University of Manchester with a range of lithics enthusiasts and experimenters. It brought home to me again the import of thinning, and difficulty explaining how it works. I have a better understanding of the problems of steep angles now, they are simply pressure flaking platforms waiting to be exploited. All good, but I was not able to get anyone to get a piece thinner than 6mm. This is effectively the original thickness without bifacial thinning. I know from my own experience, and actual Bronze Age arrowheads on the Portable Antiquities database, that 5mm is necessary to have a good chance of successful notching. I need to be able to do it consistently, and then explain how I am doing it. That is my next learning and teaching task, transitioning from doing to facilitating. I am going to see if anyone is interested in a thinning and notching session. On the plus side, drawing attention to the sound of the hits was indeed a useful strategy.