Estudio de algunos materiales pictóricos utilizados por Zuccaro en las obras de San Lorenzo de El Escorial

Three envelopes containing blue powdered pigments for painting were found in the general archives of Simancas, Spain. An investigation revealed that these materials could be related to two letters sent by Federico Zuccaro to Venice in which he ordered colours and brushes he would need for his work at the monastery of San Lorenzo de El Escorial. It was concluded that these pigments were showpieces used to define the desired quality of the colours. In this work, the content of the letters is commented and the pigments analysed, yielding ultramarine blue and smalt. This is followed by a review of the Spanish and Italian technical literature of that period in order to understand why Zuccaro needed to import some products from Venice. Finally, the transcription of the letters studied in this work is presented in appendix.