|The lady in reds. Credit: |
Art Institute of Chicago
Carmine itself is produced from the cochineal beetle, a native of the Americas which infests cactus leaves. (A neat overview of carmine production is here. ) Carmine was introduced to European artists by the Spanish, and the pigment became especially popular during the Renaissance, when it was prized for creating translucent, glowing washes. In addition to the brilliant red-pink pigment, the cochineal beetle extract can be precipitated with copper sulfate to create Indian purple.
The Art Institute has several works in its collection in which carmine-based pigments used during painting have since faded.
surface-enhanced Raman spectroscopy, an enhancement of of Raman scattering detection optimized for anticipated low target abundances or for weak scatterers. (A YouTube overview of the method, which is widely used in forensic applications, is here).
You can see can see a reconstruction of how the original might have looked at the BBC web page here. The most apparent difference is in the background, which has much more raspberry than the present-day painting.