Our thanks to Rod MacKenzie who presented an excellent workshop on slag – or pyrotechnic residue! Rod brought a number of samples in and took us through all the various smelting processes and possible identification.
The bottom line being that this residue is very hard to date unless it is recovered from a sealed context.
Rod helped us list and analyse the slag remains we had found in the Dean’s garden. It looks likely that these come from more modern boiler waste.