Fig. 2

Equations in Space. a Representative KKT-corrected R-FTIR spectrum of a spot in the protrusion (layer 1). b Transmission/absorption spectrum of an unmounted fragment of the protrusion. c Distribution of zinc soaps obtained by integrating the zinc carboxylate peaks in the R-FTIR spectrum (1565–1516 cm⁻¹). d Distribution of lead white obtained by integrating the carbonate band in the R-FTIR spectrum (1551–1351 cm⁻¹). e Distribution of Prussian blue obtained by integrating the cyano absorption peak in the R-FTIR spectrum (2112–2014 cm⁻¹)