The Worship of the Golden Calf by Frans Francken II.

The technical study of The Worship of the Golden Calf by Frans Francken II (c. 1630 - 1635) was done in parallel to the painting's conservation treatment between April and July 2019 at the Hamilton Kerr Institute (HKI), University of Cambridge, where I was an Advanced Intern in the Conservation of Easel Paintings. This in order to characterize the materials and techniques used by the artist for the build-up of this painting.

This study implied a thorough observation of the surface under magnification in conjunction with different investigative imaging and analytical methods of examination. Initially, UV light photograph (UV), Raking light photography, X-Radiography (XR) and Infrared Reflectography (IRR) were performed, in addition to microphotography, which provided valuable information about historical conservation treatments, changes to composition, sequence of construction of the image, characteristics of the materials used and methods of application. Additionally, three micro samples were taken from areas adjacent to damages and losses to be mounted as cross-sections. These made possible to establish the painting stratigraphy and appreciate the morphological characteristics of the layers. Finally, Micro X-Ray Fluorescence (XRF) analysis was also carried out to determine the elemental composition of the paint layers and to aid in the identification of the pigments used by the artist.

Frans Francken II. The worship of the golden calf , c.1770, Oil on panel, 56.7cm x 86.2cm. Fitzwilliam Museum, Cambridge, UK. Photography taken by Chris Timus, ©Hamilton Kerr Institute.

The painting The worship of the Golden Calf in the Fitzwilliam Museum constitutes one of many versions of this subject matter produced in the prolific workshop of Frans Francken II. The scene depicts the Israelites eating, drinking and flirting at tables arranged around a pillar on which the golden calf effigy stands, while at the left stands an incredulous, furious Moses breaking the ten commandments.

X-ray composite -The worship of the golden calf- Taken by Chris Timus, ©Hamilton Kerr Institute.

Support

The painting support is a landscape format panel with horizontal grain comprised of three oak boards radially cut and horizontally butt-jointed. Two dowels were used in each joint to ensure an accurate alignment and reinforce the joint (see X-ray composite). All four edges exhibit a slightly uneven 5mm bevel, which suggests the panel is the original size and has not been cut down.

A white ground layer, made in two applications, covers the entire reverse of the panel. It is visible both through abrasions to the priming layer and through several small losses. Cross-section analysis suggests this ground layer is made of chalk bound in a proteinaceous medium (amido-black staining). The oil-based brown priming is pigmented, thin, brushy and uneven. Additionally, it exhibits an orange fluorescence in UV light.

Cross Section #3 taken from the back. Three application of a chalk glue layer plus a oil pigmented priming.

Whole back -The worship of the golden calf- Taken by Chris Timus, ©Hamilton Kerr Institute.

Preparation layers:

The front of the painting exhibits a white colour ground comprised of two layers of chalk and a proteinaceous binding medium, probably animal glue. It is visible in areas where some paint losses have occurred. Raking light examination shows an uneven application and suggests the use of a knife, as some undulations can be seen in the middle top part of the panel. No smoothing seems to have been done at this point.

Across the whole panel, on top of the ground there is a thin (microns) pigmented oil isolation layer, predominantly rich in carbon black, with the presence of lead white and some red and brown pigment particles. It corresponds to a streaky imprimatura or primuersel common in seventeen-century Flemish painting. This layer was applied in multiple directions, using a 2cm flat brush, which can be clearly seen on close examination of the painting due to the transparency of the paint layers and also in infrared reflectography. This layer was probably applied to reduce the absorbency of the chalk ground and fix the preparatory drawing while giving a tonal base on top of which the final image could be built-up. It exhibits some pinholes due to air bubbles on the surface, which are notorious in the left bottom corner.

Cross-section taken from the bottom left corner. Photographed at 200× magnification in Darkfield. Notice the two applications of ground and the streaky imprimatura on top.

Detail showing the painting surface texture in raking light.

IRR image -The worship of the golden calf-. Taken by Chris Timus, ©Hamilton Kerr Institute. Notice the streaky imprimatura used by the artist and the presence of pencil underdrawing at the top right side-

Detail of IRR image showing the underdrawing.

IRR imaging made possible to identify free-handed underdrawing done in dry media carbon black exclusively on the upper-left part of the painting in the area of the trees. Traces of this underdrawing could also be spotted in visible light under magnification. The fact that the main preliminary sketch of the painting was not detected using this specific examination method suggests that the artist used a non-carbon based dry or wet media like for instance red chalk, metal point or red paint oil.

Both the X-ray and the IRR also made visible changes in the composition such as the subtraction of two big tents at each side of the painting.

Paint layers:

The painting build-up was achieved mostly using opaque and semi-opaque oil paint layers, on top of which the artist added selective glazes and impastos according to the passage depicted. Glazes can be observed mainly on the fabric drapery while impastos, clearly seen with raking light, are exclusive to the main scene detail highlights (food, jewellery, hair, costumes). Examination under magnification shows the use of medium-sized brushes for achieving the landscape and the use of fine brushes for completing the details.

The paintings palette identified with spot micro XRF is most likely comprised of lead white, lead tin yellow, vermillion, earth pigments, umber, copper greens, smalt, azurite, red and yellow lakes. This is consistent with what was observed in the two paint samples taken from the front and mounted as cross-sections.

Micro spot XRF spectra taken from the yellow drapery. Mayor elements detected: Lead (Pb), Tin (Sn), Calcium (Ca), Mercury (Hg). Minor elements detected: Cooper (Cu), Manganese (Mn), Iron (Fe)- Possible pigments present: lead white, lead tin yellow, vermillion, earth pigments, cooper greens.

Cross-section taken from the sky. Notice the sharp and angular blue particles of smalt in combination with lead white and a small amount of azurite (greenish blue particles).

Maria Carolina Peña Mariño

Easel Painting Conservator

The Worship of the Golden Calf by Frans Francken II.