CONSERVATION OF THE DARNAULT MIRROR: AN ACRYLIC EMULSION COMPENSATION SYSTEM
CYNTHIA MOYER, & GORDON HANLON
We feel that this system of compensation fulfills many of the requirements we initially sought. It is not only chemically distinguishable from the original water gilding but also physically distinguishable upon very close inspection. It is reversible should reinterpretation of the object be necessary in the future. It is a compensation method to which one can add varying degrees of gold leaf and/or mica or gold powders, depending on the requirements. A perfectly smooth gesso surface is not imperative for this system, as the inpainting and leaf application are selective. This procedure reduces preparation time and the introduction of additional gesso on original gesso surfaces. This system does not require a toner over the powders, just over the leaf. After the barrier coat application, only one layer in two colors is applied to areas of loss prior to the application of leaf or powders, establishing a very thin surface layer addition. As a result, original recutting details in the gesso are not lost.
Some difficulties and criticisms of the acrylic emulsion inpainting mordant arose in practice and may present themselves in the future. Color matching was a challenge because the acrylics dry darker than they do when mixed wet. They tend to be rubbery to work with, not flowing enough to provide the impeccably smooth surface sought in gilding grounds. Some of the mica pigments are more metallic, more “glittery” looking, and only the very finely ground powders are suitable in this application. The Li-quitex forms a poor bond with the Soluvar matte medium, a desirable quality in terms of reversibility but, in application, it may bead on the surface of this barrier coat when thinned with too much water. The question of the cross-linking potential of an acrylic in the future and its continued reversibility in the long run should be kept in mind (Horie 1987). Presently, the system can almost be peeled off the Soluvar, but otherwise, the acrylics are soluble in acetone, xylene, or toluene, and the Soluvar in mineral spirits. We question also whether the Triton X-100 component of the xylene, water, and Triton X-100 emulsion cleaning system is fully cleared from the porous gesso and to what degree the Soluvar matte is intractable from these areas. However, in spite of these concerns, the system fulfills our material and aesthetic requirements for displaying the mirror frame, both in context in the gallery and in its own right, on its own. Like any conservation treatment, it is a choice, based on many factors. We feel we have, however, indeed struck a balance.
We would very much like to thank John Childs, Brian Considine, Kathy Gillis, Joe Godla, Montserrat LeMense, Mark Leonard, Nancie Ravenel, and Gillian Wilson, all at the J. Paul Getty Museum at the time of this treatment, as well as Jonathan Thornton and Richard Wolbers for their contributions to this project.