Surfaces and pigments – Les Globes de Mercator de l'UNIL

Before (above) and after (below) the colour samples were taken from the terrestrial globe (left) and celestial globe (right), Ill. HKB|HEAB report.

Identifying the colour pigments used on the terrestrial and celestial globes (red, green, blue, brown and black printing plus black paint) required a range of tests :

785nm Raman spectroscopy for the pigments,
FTIR (Infrared) spectroscopy for the binders,
scanning electron microscopy (SEM) with energy-dispersive spectroscopy (SEM-EDS).

Microsamples were collected at UNIL’s Forensic Science Institute by Dr Nadim Scherrer of HKB|HEAB and Dr Stefan Zumbühl. They drew red, green and brown-black pigments from the terrestrial globe and red, green and yellow/green pigments from the celestial globe.

The report concluded that all the components identified by the analyses were available at the time the globes were manufactured (around 1540). The heterogeneity and mild chemical degeneration of the green pigments suggested either deterioration or the use of a mineral product.

Red pigmentsGreen pigmentsBrown-black pigmentsBinders

Terrestrial globe – bright red : lead red, traces of hematite

: GT p1

: GT p1

Celestial globe – dark red : litharge, lead red

: GC p1

: GC p1

Terrestrial globe – green : copper-based pigment tinged with chlorine (or degradation product containing chlorine)

: GT p2

: GT p2

Celestial globe – green : copper oxalate dihydrate

: GC p2

: GC p2

Terrestrial globe – brown-black printing ink : red/brown iron oxide : hematite, unidentified black phase

: GT p3

: GT p3

Celestial globe – brown-black printing ink : iron oxide, green copper pigments, gypsum

: GC p3

: GC p3

Terrestrial globe – red colour : proteins, resin (probably from the varnish); traces of oil cannot be ruled out (presence of lead carboxylates but the spectra overlap)

Celestial globe – green colour : oil, possible but unconfirmed presence of proteins (the spectra overlap)

Find out more

Analytical report : Kunsttechnologisches Labor, Graduate School of the Arts in Bern (HKB|HEAB), Ref. No. HKB1406101Ext, 20.09.2014, Dr Nadim Scherrer & Dr Stefan Zumbühl, Bern.