Using Raman spectroscopy, London-based chemist Robin Clark and his collaborators analyzed the pigments used for the miniatures illustrating various copies of Gutenberg’s Bible .
The Raman effect is due to the incidence of a photon incident on a molecule and the consequent interaction with the electron cloud of its bonds, exciting the molecule to a virtual state.
Thanks to this we know what the colors of the Bible are made of:
- Red: probably cinnabar (mercury sulfide) or hematite (iron oxide).
- Blues: azurite, lapis lazuli or indigo.
- Oranges: minium or realgar.
- Greens: malachite (basic copper carbonate) or verdin (basic copper acetate).
- Yellow: basic lead carbonate or lead stanate.
- Ocher: goethite (a basic oxide of iron).
- Blacks: charcoal.
- Whites: calcite.
As Santiago Álvarez explains in Of women, men and molecules: "A splendid palette that resists the passing of the centuries wonderfully".
The Gutenberg Bible is an edition of the Vulgate, printed by Johannes Gutenberg in Mainz, Germany, in the 15th century.