Hanekam-Decorated Donderglas: Revised Catalogue Entry
The catalogue entry for our early-18th-century Hanekam-decorated donderglas has been rewritten and expanded, with new photographs added — including images under ultraviolet light.
We have thoroughly revised the catalogue entry for the Hanekam-Decorated Donderglas (Southern Netherlands, first half of the 18th century). The updated description covers the pear-shaped reservoir with its cockscomb (hanekam) droplet ornament, the rare brass mount and suspension, the numbered spout scale, and the working principle of this early Dutch thermo-barometer, together with a note on its origins in the tradition of Cornelis Drebbel and Gijsbrecht de Donckere.
A new section examines the glass itself. Under ultraviolet light the body fluoresces green, but daylight examination and a Geiger check rule out uranium: the glow comes from manganese, the "glassmaker's soap" long used to decolourise glass. The entry explains why manganese fluoresces and how it differs from uranium (vaseline) glass — a distinction that also supports the early dating.
The entry is now illustrated with new photographs, including images taken under ultraviolet light that show the fluorescence described in the text.