The daily routine of the goldsmith is plagued with unexpected problems such as random casting defects, which are very difficult to diagnose properly. This often causes a big waste of time and useless attempts to find the right solution. From our archive of defect analyses collected over a ten-year period, we selected cases involving hard spots commonly occurring and difficult to diagnose correctly with the resources normally available in a goldsmith's laboratory. It can be stated that the usual definition of hard spots actually identifies a defect which, even when displaying the same appearance (under the naked eye or at low magnification), are a consequence of different causes. Basing our assumptions on such considerations, we sketched a detailed classification of various classes of hard spots, providing a series of causes and possible solutions.

Author(s): Damiano Zito, Silvano Bortolamei, Mauro Di Siro, Daniele Maggian, Andrea Trentin, Alessandro Zocca