The Hours of Isabella Stuart

Underdrawing

Artists' Techniques

The extensive underdrawing in brown ink which is revealed in the majority of the illuminations, both through thinly laid colours or paint losses and in the near-infrared images, is crucial in distinguishing between the three main artists. 

A substantial amount of underdrawing and frequent changes of mind at the painting stage are typical of the Giac Master and the two assistants who painted large miniatures.

The Rohan Master’s work is characterised by elaborate drawing of an idiosyncratic nature. Strings of curly loops resembling doodles and brushed over with a grey ink wash cascade down fabric folds or congregate into pools of drapery.

The Madonna Master instead painted both of his miniatures freehand: neither shows any underdrawing.

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FORS analysis (above) of a blue leaf shows characteristic features of both azurite and ultramarine, due to the fact that the area analysed by this method measures 3-4 mm across and therefore encompasses both the light and the dark blue portions of the leaf. The Raman spectrum (below) recorded on a micrometric portion of the dark blue shading shows a clear spectrum of ultramarine blue.
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Detail of the open book under magnification (12.5x), showing extensive losses in the lead white paint layer, with a pattern typical of the images painted by the Rohan Master in this volume.

Accompanied by his symbol, the lion, and looking up for divine inspiration, St Mark prepares to write his Gospel. The marginal scene showing the Flight into Egypt belongs to the cycle illustrating the Pilgrimage of Jesus Christ. The arms of Isabella Stuart have been added to the border.

Technical analyses revealed that ultramarine blue was used to paint Saint Mark’s blue tunic and the lion’s wings as well as the Virgin’s mantle in the side miniature. The rubric was also written with ultramarine blue ink. The blue leaves which surround the decorated initial were painted with azurite instead and shaded with dark blue ultramarine (hotspot 1). Surprisingly, the blue squares which form the diamond pattern in the miniature’s background were painted in ultramarine only in the lower portion of the background (below the figures of St Mark and the lion), while azurite was used for the upper portion of the decoration. This suggests that the Rohan Master painted the lower part of the background around the figures, but left the background’s completion to an assistant who used the cheaper blue, azurite.

The presence of two different blues in the background is confirmed by the infrared image, where ultramarine appears light and azurite dark (see Infrared Layer). The same image reveals the presence of elaborate underdrawing, also visible through the semi-transparent paint layers of the apostle’s pink robe. Its peculiar style is typical of the Rohan Master.