THE PURPOSE of the following report is to describe a trial set up to test the practicability of extending the effective working life of a cutting emulsion and to investigate the nature of the problems associated with biochemical breakdown. The trial covered a period of more than two years, with a break of two months in the middle, when the treatment was withdrawn to assess the validity of the results of the initial period. It is hoped that the success of this work will be of interest and value to others working in this field.