Alessandro Volta (portrait by N. Cianfanelli) was the first modern scientist who aimed to rank dielectric materials. No such rankings have proven accurate because of the effects of material transfer, as described by B. A. Grzybowski and co-workers in their Communication on page 4843 ff. In the picture, the upper half of the circle illustrates a typical ranking of contact charging (red=positive polarity, blue=negative polarity). The lower half shows atomic force microscopy images of contact-charged surfaces.