Additional file 1
The influence of light and relative humidity on the formation of epsomite in cadmium yellow and French ultramarine modern oil paints
Jessie Harrison
a, Judith Lee
b*, Bronwyn Ormsby
b, David Payne
a,c,
a Department of Materials, Imperial College London, Royal School of Mines Building, Prince Consort Road, South Kensington, London SW7 2BP, U.K.
b Conservation Science Department, Tate, Millbank, London SW1P 4RG, U.K.
c Research Complex at Harwell, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0FA, U.K.
*Corresponding author: judith.lee@tate.org.uk
1. Images of paint samples
The paint samples were photographed after ageing as shown in Fig. 1. Samples aged at low 23% RH were not included in this research.
Figure 1 Photographs of W&N AOC cadmium yellow and French ultramarine tube paint samples, prepared on either oil-primed canvas and acrylic-primed canvas, after 6 weeks artificial ageing under 23 % RH ambient light/ambient dark, 50 % RH ambient light/ambient dark, or 75 % RH elevated light/near-dark.
2. EDX spectra for the W&N tube paints
Figure 2 EDX spectrum for W&N AOC Cadmium Yellow tube paint.
Figure 3 EDX spectrum for W&N AOC French ultramarine tube paint
3. W&N AOC French ultramarine x-ray diffraction (XRD)
The XRD pattern for the French ultramarine paint films are dominated by the Na8[SiAlO4]6·(S3)2 pigment and Al2Si2O5(OH)4
(kaolinite) (Figure 3). However, after ageing at 75 % RH/elevated light, the emergence of diffraction peaks at 14.7 ° and 29.7 ° is attributed to the crystal formations observed under LM and SEM as described in the main manuscript. Unfortunately, these could not be positively identified due to the relatively low intensity of the peaks. No MgSO4 was detected after ageing at 75 %
RH/elevated light using XRD. This absence may suggest the MgSO4 surface scale is amorphous.
Figure 4 XRD pattern for W&N AOC French ultramarine on acrylic-primed canvas after ageing at a) 50 % RH, ambient light; b) 75 % RH, elevated light conditions.
References
[1] J. Jamieson and G. Frost, “The heats of crystallization of vacuum dehydrated magnesium sulphate heptahydrate and cobaltous chloride hexahydrate,” Can. J. Chem., vol. 34, pp. 583–590, 1956.
