Blast fragmentation data in the form of percentile fragment sizes as function of specific charge often form a set of straight lines in log(size)-log(energy) space that tend to converge on a common focal point. Single-hole shots in specimens of virgin material clearly show this and the phenomenon is called the fragmentation-energy fan. Field data from bench blasting in rock scatter much more but may be interpreted to form such fans. The slopes values of the fan lines depend primarily on the percentile level. This property can be derived from sieving functions of the form P[ln(x/x_max)/ln(x_max/x₅₀)]. An example is
the Swebrec function when the parameter b is constant.
The fragmentation-energy fan and associated sieving function contradict two basic assumptions of the Kuz-Ram model; i) that the Rosin-Rammler function reproduces the sieving data well and ii) that the uniformity index n = constant and independent of q. This favors formulating fragmentation prediction formulas instead of the Kuz-Ram way as a set of percentile fragment sizes, parameters that by definition are independent of the size distribution. A generalization of the fan behavior to include non-dimensional fragment sizes and an energy term with implicit size dependence seems possible to make.