Since 1919, the potassium chloride/ammonium nitrate mixture was gradually replaced by a 50/50 mixture of ammonium
sulphate and ammonium nitrate called "mischsaltz". This highly hygroscopic mixture had the disadvantage of clogging
together under the pressure of its own weight during storage. It was common practice to loosen the "aggregated”
product by firing explosives in holes drilled using a jumper bar in the hardened mass. Until the day of the accident over
20,000 firings were carried out in the "mischsaltz" without any sign of accident being observed.