Many of the works on paper currently on view in Historic Images of the Greek Bronze Age: The Reproductions of E. Gilliéron & Son required conservation treatment to address a variety of structural and aesthetic problems. The dedicated effort over the past two years to address the conservation of these objects and to look more closely at their method of production reflects a reconsideration of their role in the Museum and in the history of art itself.
The Gilliérons were employed by Sir Arthur Evans as restorers during the excavation of the site at Knossos, Crete. The completed restoration represented the frescoes as the Gilliérons believed them to have looked originally, and the paintings on paper that the father-and-son team created convey their process and technique in that endeavor. Today, our primary goal as paper conservators is to preserve these works and ensure their longevity in the Museum's collection; they are approached as unique works of art on paper painted by the Gilliérons, with respect for the artists’ original intent.
The paintings in gouache, or opaque water-based paint, were acquired by the Metropolitan Museum between 1907 and 1925 shortly after they were made. Most were painted on paper lined with linen canvas, then stretched on strainers and framed in the manner of paintings. Three were painted on paper mounted overall to heavy woodpulp board.
Two years ago, when the paintings were brought to the Department of Paper Conservation in preparation for exhibition, they had been off view for decades and were found to have a range of condition issues. The paper supports were darkened and brittle, typical of a paper made with groundwood fibers and sized with alum-rosin, a nineteenth-century industrial size notorious for its tendency to discolor irreversibly and weaken paper as it ages. At the time the Gilliérons were working, this type of machine-made paper was the only option for such large-scale drawings using one sheet. In many cases the gouache was flaking in discrete areas, a condition that was exacerbated by the eruption of sulfate salts possibly caused by an interaction between the sulfurous residue of the paper's sizing and the zinc white gouache base.
The conservation treatment of this collection varied from object to object, with the first priority being the improvement of the paintings’ mounting and housing in service to their long-term preservation. Surfaces were cleaned of dirt and accretions, flaking paint was consolidated with a reversible adhesive, and the drawings were re-mounted using archival and inert materials commonly used in conservation mounting.
Concurrent with the conservation treatment, conservators and conservation scientists were able to examine the collection to make inferences as to how the drawings were made and about the nature of their relationship to the wall paintings themselves.
The drawings were examined using a variety of nondestructive methods, including infrared reflectography, an imaging technique that allows conservators to view underdrawings made using carbonaceous materials. Interestingly, even though the Gilliérons made multiple copies of the images, minor adjustments visible in the graphite-pencil underdrawings indicate that the works were drawn freehand rather than with the employment of a matrix or transfer method.
According to Sir Arthur Evans's published accounts of the excavation, he employed a scientific assistant named Noel Heaton on site at least as early as 1909. Heaton chemically analyzed the pigments used by the Minoans for the wall paintings and published his results in 1910. As evidenced by his findings, the Minoans painted with earth colors—red and yellow ochre, bone or soot black, and lime white—along with one of the earliest artificial pigments, Egyptian blue, or calcium copper silicate. Through analysis of their pigments using X-ray fluorescence, we find that the Gilliérons used vermillion, cadmium yellow, and cerulean blue—modern pigments comprising a more vibrant palette than that of the Minoans. The paint contains a gum binder, which was identified via ELISA protein analysis, and zinc white mixed with every color, a likely formulation for a commercially prepared gouache. The zinc white base of the gouache paint increased opacity and covering power and created a matte appearance appropriate for emulating fresco painting.
For the reproductions made on plaster, the principle pigments identified by X-ray fluorescence were the same as those used in the watercolors, with the addition of lead white found in each area examined, possibly indicating a lead-white ground under the same paint used for the works on paper. However, extensive past restorations of the works in plaster make a positive pigment and binder identification impossible and also prevents the characterization of the fresco technique as either a secco (paint on dry plaster) or buon fresco (paint on wet plaster).
Exhibition: Historic Images of the Greek Bronze Age: The Reproductions of E. Gilliéron & Son
Author's Note: I would like to gratefully acknowledge the contribution of technical analysis by the following scientists from the Department of Scientific Research: Silvia Centeno performed RAMAN analysis on the erupting salts, Tony Frantz performed XRD on the erupting salts and XRF on pigments found on a Gilliéron plaster fresco reproduction, and Julia Schultz, Julie Arslanoglu, Adriana Rizzo, and Dina Georgas performed FTIR and ELISA protein analysis on the binding media. I performed XRF analysis on the pigments in the works on paper as well as the micro-chemical testing for rosin sizing and PLM for fiber analysis.