Systematic CR-39 bulk etching experiments were conducted over a wide range of concentrations (2-30 N) of NaOH-based etchant. Critical analysis and a deep discussion of the results are presented. A compre-hensive nuclear track chemical etching data bank was developed. Three regimes of CR-39 bulk etching were identified. Regime I spans etchant concentrations from 2 to 12 N. Regime Ⅱ spans concentrations from 12 to 25 N. We call this the dynamic bulk etching regime. Regime Ⅲ is for concentrations greater than 25 N. In this regime, the bulk etch rate is saturated with respect to the etchant concen-tration. This classification is discussed and explained. The role of ethanol in NaOH-based etchants is explored and discussed. A parameter called the‘‘reduced bulk etch rate’’ is defined here, which helps in analyzing the dependence of bulk etching on the amount of ethanol in the etchant. The bulk etch rate shows a natural logarithmic dependence on the density of ethanol in the etchant.