UV light (right), visible light (left)
Since the 1950s, the fluorescence of varnish layers under UV light has been used as an aid to interpret the varnished surfaces of vintage instruments.
Fluorescence is the ability of certain substances to emit light for a short time when exposed to a high-energy radiation source. This allows the ingredients of different paint layers to be made visible. Even if it is not possible to make clear conclusions about the material composition of the varnishes on the basis of fluorescence, it is possible to identify characteristic features of the varnish coating. Thus, retouching varnishes applied subsequently can be easily detected.
