This mercury then reacts with the remaining chloride resulting in the black changing to white. First of all, very tiny amounts of chloride combined with light to produce globules of metallic (pure) mercury that are visible on the painting as black patches. Recent research has shown that this occurs in two phases under the influence of the chloride present in the air. The mercury vermillion would in time lose its colour intensity due to chemical changes. Prisoners were used to mine the mercury, many of whom succumbed in the mine shafts to the fatal mercury vapour.Īt the end of the 19th century the original vermillion was superseded by the red cadmium pigment, which in addition to being better for one’s health is also more durable. The mercury was extracted from mercury mines, the largest of which can still be found near the Spanish city of Almadén. The heating process was an art in itself, and in the 17th and 18th century skilled Dutch ‘vermillion heaters’ earned an international reputation with their excellent ‘vermillion pots’. This would produce a red mercury sulphide or vermillion. This was done by heating a mixture of mercury and sulphur in a pot sealed with clay. It is generally accepted that vermillion could be produced synthetically already back in the eighth century. For the trainee journeymen of the Renaissance and Baroque periods it was therefore hard work to get the required intense red orange colour from the hard mineral. The 15th century painter Cennino Cennini writes about this in his famous ‘The Craftsman’s Handbook’: ‘If you were to rub it every day for twenty years it would simply become better and more perfect’. The finer the grinding, the fierier the red. The mineral itself is deep red and has to be ground to a pigment before it can be used in paint. The Romans even processed it in lipstick, which certainly did no good to the health of the ladies. Unaware of the harmful consequences for one’s health, vermillion was extracted from mercury and sulphur-rich cinnabar long before the common era. Vermillion: from mercury and sulphur to harmless pigments
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