TY - JOUR
T1 - A systematic examination of colour development in synthetic ultramarine according to historical methods
AU - Hamerton, Ian
AU - Tedaldi, Lauren
AU - Eastaugh, Nicholas
PY - 2013
Y1 - 2013
N2 - A number of historical texts are investigated to ascertain the optimum conditions for the preparation of synthetic ultramarine, using preparative methods that would have been available to alchemists and colour chemists of the nineteenth century. The effect of varying the proportion of sulphur in the starting material on the colour of the final product is investigated. The optimum preparation involves heating a homogenised, pelletised mixture of kaolin (100 parts), sodium carbonate (100 parts), bitumen emulsion (or any 'sticky' carbon source) (12 parts) and sulphur (60 parts) at 750°C for ca. 4 hours. At this stage the ingress of air should be limited. The sample is allowed to cool in the furnace to 500°C, the ingress of air is permitted and additional sulphur (30 parts) is introduced before a second calcination step is undertaken at 500°C for two hours. The products obtained from the optimum synthesis have CIE ranges of x = 0.2945-0.3125, y = 0.2219-0.2617, Y = 0.4257-0.4836, L* = 3.8455-4.3682, a* = 4.2763-7.6943, b* = -7.6772-(-)3.3033, L = 3.8455-4.3682, C = 5.3964-10.8693, h = 315.0636-322.2562. The values are calculated using UV/visible near infrared spectra using Lazurite [1], under D65 illumination, and the 1931 2° observer.
AB - A number of historical texts are investigated to ascertain the optimum conditions for the preparation of synthetic ultramarine, using preparative methods that would have been available to alchemists and colour chemists of the nineteenth century. The effect of varying the proportion of sulphur in the starting material on the colour of the final product is investigated. The optimum preparation involves heating a homogenised, pelletised mixture of kaolin (100 parts), sodium carbonate (100 parts), bitumen emulsion (or any 'sticky' carbon source) (12 parts) and sulphur (60 parts) at 750°C for ca. 4 hours. At this stage the ingress of air should be limited. The sample is allowed to cool in the furnace to 500°C, the ingress of air is permitted and additional sulphur (30 parts) is introduced before a second calcination step is undertaken at 500°C for two hours. The products obtained from the optimum synthesis have CIE ranges of x = 0.2945-0.3125, y = 0.2219-0.2617, Y = 0.4257-0.4836, L* = 3.8455-4.3682, a* = 4.2763-7.6943, b* = -7.6772-(-)3.3033, L = 3.8455-4.3682, C = 5.3964-10.8693, h = 315.0636-322.2562. The values are calculated using UV/visible near infrared spectra using Lazurite [1], under D65 illumination, and the 1931 2° observer.
KW - Aluminum Silicates
KW - Color
KW - History, 19th Century
U2 - 10.1371/journal.pone.0050364
DO - 10.1371/journal.pone.0050364
M3 - Article (Academic Journal)
C2 - 23418413
SN - 1932-6203
VL - 8
SP - e50364
JO - PLoS ONE
JF - PLoS ONE
IS - 2
ER -