I recently came across a book of Agfa photo chemistry formulas from the thirties - one formula is called a "Chrome Alum Hardening Bath" and it is used in place of a regular stop bath (short stop as Agfa calls it). Its purpose is to give additional hardening to the film, particularly in hot weather or for tropical development.

It's 30 grams of Potassium Chrome-Alum to one liter of water.

Is anyone familiar with this, or have an opinion as to whether it may help with the Efke scratches?