Spectroscopic analysis used to uncover the original paint colour of the Helsinki Government Palace tower clock faces

Heritage Science

Table 1 Paint layers found in the clock west face/VN1 (over a copper plate) and east face/VN2 (over an iron plate)

Clock face	Colour	SEM-EDS	Raman bands (cm⁻¹) and assignments
VN1/VN2	Red	Fe and Ca	Hematite (224, 290 cm⁻¹), red lead (123, 150, 313, 390, 548 cm⁻¹)
VN1/VN2	Black	C	Carbon black (1345, 1585 cm⁻¹)
VN1/VN2	Red	Al, Si and Fe	Hematite (224, 290 cm⁻¹), red lead (123, 150, 313, 390, 548 cm⁻¹)
VN1/VN2	White	Ti, Ba, Pb and S	Lead white (1050 cm⁻¹)
VN1/VN2	Grey	Ti and Ba mainly, together with S, Pb, Fe and Cr	Prussian blue (274, 532, 2089, 2117, 2153 cm⁻¹), phthalocyanine blue (745, 1526 cm⁻¹), titanium white (446, 609 cm⁻¹) and carbon black (1345, 1585 cm⁻¹)
VN1/VN2	Blue	Ca, Mg and Fe	Prussian blue (274, 532, 2089, 2117, 2153 cm⁻¹), phthalocyanine blue (745, 1526 cm⁻¹)
VN1/VN2	Yellow	Cr, K and Zn	Zinc chromate (342, 871, 891, 940 cm⁻¹), lead oxide (142 cm⁻¹), barium sulphate (986 cm⁻¹)
VN1/VN2	White	Ti, Ba and S	Titanium white (446, 609 cm⁻¹), barium sulphate (986 cm⁻¹)
VN1	Light blue	Ti, Ba, Cu and S	Titanium white (446, 609 cm⁻¹), barium sulphate (986 cm⁻¹), phthalocyanine blue (745, 1526 cm⁻¹)