Technique of execution

 

Fig. 6: next to the detail of the decoration of the cloak, the image obtained with the optical microscope of a polychromatic sample. We may see the inferior layer of glitter followed by a greenish patina.

Fig. 7: image obtained with the optical microscope of a sample of the covering of the scroll holder. We may identify remainders of the wood fibres that show the manufacture of the paper that was used.

The original polychrome only covered specific areas of the sculpture, particularly Nero’s cloak, in addition to the scroll holder and part of Seneca’s clothing. The polychrome areas have an initial layer that functions as a base made of red ochre and animal size, over which the artist applied a mixture of pigments: barium white, zinc white, red ochre and minium (red lead), bound with linseed oil.

The decoration of the collar and edge of Nero’s cloak originally appeared golden due to the application of metallic powder (an alloy of copper and zinc), to which an oil patina was applied to tone down the shine. Prior to restoration this gold appeared dark green in colour due to the oxidisation of the copper.

Other materials identified include vegetable and wood fibres used in the interior of the work to give greater stability and resistance to specific, fragile elements, as well as paper used to give the impression of leather covering the scroll holder for aesthetic purposes.

 
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