When we were doing the 'Silver Gelatin' book there were a few avenues that looked promising but there was not enough time to follow them up. One was the idea of using a ready-made commercial gold toner as an emulsion additive for hyper sensitivity, containing as it does a source of both gold salts and sulphur. An initial test was made by Phil Robbins, who added a small diluted volume of Tetenal Gold Toner to the mix in the early stages of emulsification, which used an inert photographic emulsion. There was an amazing increase in activity of the final emulsion; unfortunately the fog went up to match it. We didn't take the idea any further but always meant to come back to it - maybe Photo Engineer could give a comment on this?