Detection of Ca excesses in NGC 6752 (left panels) and NGC 7078 (right panels). In the upper left panels GC stars (blue squares) are superimposed to field stars (with typical error of 0.08 dex), and all abundances are linearised in the upper right panels (see text). Generalised histograms of the [Ca/H] values for field (grey area) and GC stars (blue area) are in the lower left panels and the cumulative distributions are shown in the lower right panels, together with the probability of the two-tailed K-S test.