A calculational and experimental procedure is developed to eliminate nearly all of the uncertainties in the source and foil corrections required in most age experiments. The calculations are rigorous and yield, in addition to flux ages, values of actual foil activation at the exact spatial positions of the measurements; comparisons with experiment therefore involve fewer assumptions and produce more information. Being required in the calculations, the angular sensitivity of Cd-covered In foils is determined theoretically and checked with measurements. Comparisons between new calculations and data from old activation experiments with fission and Na-Be sources in water are made; the results suggest that a new type of fission source experiment is still called for.