Fast Fills for Big Gaps Author: Rachel C
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Article: Fast Fills for Big Gaps Author: Rachel C. Sabino Source: Objects Specialty Group Postprints, Volume Twenty-Four, 2017 Pages: 454–471 Editors: Emily Hamilton and Kari Dodson, with Tony Sigel Program Chair ISSN (print version) 2169-379X ISSN (online version) 2169-1290 © 2019 by American Institute for Conservation of Historic and Artistic Works 727 15th Street NW, Suite 500, Washington, DC 20005 (202) 452-9545 www.culturalheritage.org Objects Specialty Group Postprints is published annually by the Objects Specialty Group (OSG) of the American Institute for Conservation (AIC). It is a conference proceedings volume consisting of papers presented in the OSG sessions at AIC Annual Meetings. Under a licensing agreement, individual authors retain copyright to their work and extend publications rights to the American Institute for Conservation. Unless otherwise noted, images are provided courtesy of the author, who has obtained permission to publish them here. This article is published in the Objects Specialty Group Postprints, Volume Twenty-Four, 2017. It has been edited for clarity and content. The article was peer-reviewed by content area specialists and was revised based on this anonymous review. Responsibility for the methods and materials described herein, however, rests solely with the author(s), whose article should not be considered an official statement of the OSG or the AIC. OSG2017-Sabino_tip_layout.indd 1 12/3/19 5:46 AM FAST FILLS FOR BIG GAPS RACHEL C. SABINO The best method for creating a very deep fill in semi-translucent stones such as marble is to gradually build up successive layers of material(s) to achieve a satisfactory match in both color and density. However, if the treatment must be completed in a shorter time than this more controlled method requires, the materials best suited to produce a quick set over a large volume pose problems of opacity, cost, and/or reversibility. This tip instead makes use of high-density polyethylene foam covered with a thin skin of bulked and tinted epoxy resin to achieve a time-effective, economical, reversible, and aesthetically pleasing fill. KEYWORDS: Loss compensation, Marble, Ethafoam, Epoxy resin, Onyx powder 1. THE RELIEF This large fragment of a marble relief reflects in spirit and style the avid return around 1500 to classical models and their incorporation in contemporary sculpture (fig. 1). While nothing is known of its original context or function, it most likely formed part of a commemorative or triumphal monument in Rome. Both the cornucopia beneath the putto’s outstretched proper left leg and the terminus of the swag draped over his shoulder contain oak leaves—the emblem of the formidable Della Rovere family of Bologna, from the ranks of whom two Renaissance popes hailed: Sixtus IV and Julius II. The crossed keys under an umbrella-like canopy—the armorial device for the Holy See when the papal throne was temporarily vacant—provide another potential clue as to the original source of the fragment. 2. SCOPE The object entered the collection of the Art Institute of Chicago in 1962 and received only one documented treatment in 1977, when unsightly incrustations were mechanically removed and it was cleaned with an aqueous surfactant. Consigned to storage, it languished for the better part of three decades until 2016, when it was designated as one of nearly 700 objects to be installed in the newly designed Deering Family Galleries of Medieval and Renaissance Art, Arms, and Armor opening the following spring. The relief was to be installed at considerable height in a gallery containing other stone works similarly reminiscent of the early antique. Since so many objects needed to be prepared for installation, the relief could not be given the luxury of a gradual, stratified approach to filling the largest losses. 3. CONDITION The carving is largely intact and the stone is in overall sound condition but with some surface weathering and resultant loss of detail. The papal insignia appears to be a later modification recarved from a previous form—most likely additional vegetation at the end of the swag hanging from the proper right shoulder. Recarving is suggested by the relative whiteness and less-weathered appearance of this area; its position slightly lower than the plane of the rest of the relief; the roughly keyed surface of the marble just below it; and the style of carving that differs appreciably from the rest (fig. 2). The lower half of the putto’s missing proper right arm does not lie in the same plane as the insignia, and the nature of the break edge and the condition of the exposed marble along it gives the impression that this damage predates the recarving. The front of the proper left foot is also missing. A large square notch is present at the top proper right corner, perhaps made during extraction of the relief from its original context. 454 AIC Objects Specialty Group Postprints, Vol. 24, 2017 OSG2017-Sabino_tip_layout.indd 454 12/3/19 5:46 AM 455 Fig. 1. Black-and-white image of the relief before treatment. Italian, School of Andrea del Verrocchio, Putto with Papal Insignia, 1475/1500, marble, 149.9 × 73.7 cm, The Art Institute of Chicago, 1962.100 (Courtesy of the Art Institute of Chicago) More crucially, there is a massive triangular fragment on the top proper right corner with associated chips and lacunae of varying dimensions along the break edge. In a previous campaign of stabilization, this fragment had been secured in place with four iron cramps. Over time, the expansion of the rusting metal caused the stone to cleave away from the cramps at the top and proper right-side edges, resulting in losses so significant as to expose the cramps themselves. The loss at the top edge measures approximately 30 cm long and 4 cm deep (fig. 3). The loss on the proper right side measures approximately 45 cm long and Sabino AIC Objects Specialty Group Postprints, Vol. 24, 2017 OSG2017-Sabino_tip_layout.indd 455 12/3/19 5:46 AM 456 Fig. 2. Detail of the papal insignia, likely a recarving (Photograph by Rachel C. Sabino, courtesy of the Art Institute of Chicago) 4 cm deep. The primary void also extends to a significant portion of the putto’s outermost wing feathers (fig. 4). On the verso, lesser spalls are present in association with the cramps, as is a copious amount of disfiguring rust staining, but overall the morphology of the damage is not the same as that on the exposed sides (fig. 5). Perhaps this more benign condition is attributable to their relatively more sheltered position. A significant amount of rust staining has migrated through to the front of the relief, lending it a decidedly yellow appearance. Sabino AIC Objects Specialty Group Postprints, Vol. 24, 2017 OSG2017-Sabino_tip_layout.indd 456 12/3/19 5:46 AM 457 Fig. 3. The loss on the top edge of the fragment (Photograph by Rachel C. Sabino, courtesy of the Art Institute of Chicago) 4. TREATMENT OBJECTIVE The tight time frame of this treatment, coupled with the logistical obstacles of performing radiography on such a large piece of stone, precluded exhaustive testing or definitive confirmation of the solidity of the cramps and the stability of the join. However, the familiarity conferred by repeated handling during initial examinations afforded some reassurance that the cramps, aided by a new mounting system, would continue to hold the pieces together safely. The scope of treatment was therefore confined to making aesthetic improvements with loss compensation in the two largest gaps; along the outside of the putto’s wing; along the break edge of the primary fragment on the recto; and within the square notch at the top proper right corner. In addition, wherever possible, the overall appearance of the stone would be harmonized by mitigating staining and discoloration. 5. THE DECISION TREE There were any number of methods by which to approach this loss-compensation treatment, each method presenting advantages and disadvantages. 5.1 Plaster Plaster, whose economy and ease of use made it attractive, was initially considered for filling the largest losses. Most often, plaster is too dense for filling marble (even for weathered, ancient ones that tend to be more forgiving than the highly polished decorative ones of subsequent centuries), resulting in shadows on either side of the fill. But occasionally, with skillful retouching, plaster can be a viable option for marbles Sabino AIC Objects Specialty Group Postprints, Vol. 24, 2017 OSG2017-Sabino_tip_layout.indd 457 12/3/19 5:46 AM 458 Fig. 4. The loss on the proper right side of the fragment (Photograph by Rachel C. Sabino, courtesy of the Art Institute of Chicago) that are themselves quite dense and are not positioned in such a way to receive a good deal of transmitted light. This particular object was a borderline case. It would receive no transmitted light whatsoever, but despite being relatively dense, the tonality of the marble was comparatively warm relative to plaster. This tonal discrepancy could probably have been rectified by adding pigments to the plaster before hydrating it or by a campaign of calculated retouching. Ultimately, the topography of the break edges and the presence of the metal cramps contraindicated its use. Even with the careful design and execution of dams or molds, it would have been all too easy to lose copious amounts of fill material through pinholes, slips, or faults, likely in a very messy way, nullifying the benefits of using plaster in the first place. In addition, the cramps sit slightly proud of the surface with a 3-mm gap around them (fig. 6). To look convincing, the new fills would also have to be set back this same 3-mm distance.