Figure 8. Opacity of an impregnated (left) and non-impregnated banknote (right)

From

Paper Chemistry: Past to Present – Process Engineering for Advanced Chemistry Lessons

Laura Bögge, Marco Reinmold, Arnim Lühken

World Journal of Chemical Education. 2019, 7(2), 84-89 doi:10.12691/wjce-7-2-7