Doing some Google searching for 'copper intensifier' turns up many different types/formulas/approaches. However, Google searching for "Ansco copper intensifier" shows it was $5 a package in 1960 and 'that you simply disolved the power in water and it was ready to use'.

Sadly, for copyright reasons the articles are shown only in a brief 'snippet' form. It would take a trip to a library to read the full articles.