The Ny Carlsberg Glyptotek in Copenhagen, Denmark, have a marble head of the Roman Emperor Caligula, probably carved between 39 and 41 AD, with traces of polychromy (or paint) on the surface. Although such sculptures were painted originally, it is extremely rare for any of the polychromy to survive until the present day.
The curators and conservators in Denmark wanted to study the pigments used on the marble head of Caligula and reconstruct a painted replica. Non-contact 3D laser scanning was the perfect means to do this, as traditional techniques, such as taking a mould from the original, would have damaged the delicate and important painted surface. The data captured during laser scanning was used to produce a replica marble head.
The pigments preserved on the head were analysed at the Doerner Institute, Munich, and the replica head painted in the light of their findings. It was then displayed at the Staatliche Antikensammlungen und Glyptothek in Munich as part of an exhibition entitled 'Bunte Götter' ('Painted Gods'), at the Glyptotek in Copenhagen as a part of an exhibition entitled 'ClassiColor' ('Colour in Antique Sculpture') then at 'Il Colore del Bianco', Musei Vaticani, Rome.
The video above shows the main stages of the process, including:
the original head, with a detail of the polychromy around the left eye and ear;
laser scanning the head (note the red laser light moving down the surface of the marble);
3D data from the laser scanning - the point cloud gathered by the scanning process is shown in purple, whilst the wire-mesh is shown in white;
the CNC machining of the head from a new block of marble;
a comparison of the copy and the original, following hand finishing, the copy standing on a wooden base.
Have a look at images taken during the recording process in the image gallery.
3d scanning and hand finishing by Conservation Technologies, National Museums Liverpool.
Machining by The Hothouse, Stoke on Trent
Reconstruction of colour by: