ABSTRACT
The massive use of blasting agents such as ANFO, slurries and emulsions in rock breakage has brought about an important development of initiation and priming techniques. The detonation process requires initiation energy so that it can develop and maintain stable conditions. Since the seventies, various theories have been developed on initiation, some contradictory, creating some confusion amongst operators. When blastholes have a length of less than 10 m and are kept dry, initiation of ANFO can be carried out safely with only one bottom primer. In order to minimize the risk of cut-offs originated by the detonating cord, in large diameter blastholes a multiple priming system is used. In the priming of ANFO, the efficiency of a primer is defined by its detonation pressure, dimensions and shape. Bottom priming gives maximum use of explosive energy, increasing fragmentation and displacement of the rock with a minimum of flyrock.
