3.1.13. White Gouaches

The white areas in the prints were generally the paper background left in reserve except in prints P12 and P17 where white gouaches were used. Both gouaches appeared to have the same composition based on the p-XRF analysis (S, Zn, Sr, Ba) although White 2 (W2) in P17 was much richer in Zn (Figure S30). The presence of these elements can indicate the presence or combination of barium sulfate (BaSO4), zinc white (ZnO), and lithopone (30%:70% ZnS:BaSO4) [27]. Further distinction was not possible using Raman or infrared spectroscopies as neither zinc white nor zinc sulfide in lithopone [53] are easily detected. The Zn to Ba peak ratio in the p-XRF spectrum for White 1 (W1) however was characteristic of lithopone [54] while W2 had a much higher content of Zn, suggesting that it contained zinc white and barium sulfate or lithopone.
