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Cerulean Blue in Historical Paintings: Magnesium Identification and Pigment Replication
Václava Antušková1, Jana Luxová2, Radka Šefců1
1Chemical-Technological Laboratory, National Gallery Prague, Prague 1, Czech Republic.
None:
Cerulean blue is a pigment that was introduced to the art market at the turn of the 1850s and 1860s, with its composition stated as CoSnO3. For this project, the pigment was synthesised using historical recipes and analysed. The investigation involved examining various conditions for its preparation, such as different reactants, solution concentrations, precipitate ageing times, firing temperatures and calcination times. All of the samples obtained were green in colour, and their composition was defined as a mixture of SnO2 and Co2SnO4. To gain a more accurate understanding of pigment composition, historical paint samples and commercially available pigments were analysed. These pigments were found to contain a relatively high amount of magnesium, so new pigment samples were prepared with added magnesium. The obtained samples have the desired blue colour; their composition is Mg2-xCoxSnO4 and SnO2. Using K2SnO3·3H2O as a reactant produced more reproducible results than using SnCl4·5H2O. The reconstruction of pigment production methods revealed gaps in historical recipes. The collected data allowed us to specify the composition of cerulean blue pigment as Mg2-xCoxSnO4 with a variable amount of SnO2.
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