Cross-section Analysis: FTIR Chemical Mapping (continued)
The color-coded FTIR map on the left is overlaid on the corresponding area of the sample analyzed and shown under ultraviolet light on the right. Shades of red and pink mark the location where protein was detected. The location corresponds strongly with the location of the unknown coating material. This suggests that the painting first received a temporary protein-based varnish such as egg glair or skim milk. Artists often resorted to such temporary varnishes when their paintings were needed for exhibition, but not yet dry enough to receive resin-based varnishes delivered in strong solvents capable of dissolving fresh paint layers.
FTIR Acquisition Parameters
Mode : Direct reflection/non-contact
4 wavenumber spectral resolution
50 scans/point for 23x15 point map
Aperture size set to 12 microns with 6 micron steps