The Journal of San Diego History
Spring 1995, Volume 41, Number 2
Richard W. Crawford, Editor

By Elizabeth Court
Balboa Art Conservation Center

Images from the article

A photograph taken in about 1930 of Luis de Mena’s eighteenth century painting of La Madre Santisima de la Luz recorded various types of damage which had occurred over the years. A vertical line of dark spots extended from the face of God down through the Madonna’s face and dress. Similar spots scattered in the upper background were flake losses of paint which could have been caused by water running down the reverse of the canvas at some time. Lighter spots in vertical lines approximately one-third of the way in on each side were similar losses following the vertical seams. A generally mottled and smeary look in the photograph was more difficult to interpret but appeared to be the result of some attempt at cleaning. Most serious, it appeared that the top of the canvas had been cut off including the top of God’s head and the putti on the right. A wooden frame covered the edges.

By the time the painting was acquired by the San Diego History Center in 1993 it appeared disastrously transformed. In a no doubt well-intentioned but entirely amateur attempt at restoration, the original canvas had been attached to a heavy cotton duck fabric with a thick layer of adhesive like Elmer’s glue. The front had been entirely repainted with what appeared to be oil paint. The colors were garish and the brushwork crude, made by a wide stiff brush which left prominent ridges. The overpaint was thick and opaque, covering virtually the whole surface with only tiny glimpses of the original surface, which was smoother and more subtly blended, visible in features such as the eyes of the Madonna, peering through the murky covering.

The initial questions raised were: was it possible to remove the overpaint without further damage to the fragile original paint? Was it feasible? Or was the original so damaged underneath and would the task of removing the overpaint be so time-consuming, and therefore expensive, as not to be worthwhile? Answers to these questions were sought by several methods. Small tests were conducted in selected areas with a range of organic solvents to determine the solubility of the overpaint and the original paint. These tests confirmed that the overpaint was probably at least fifty years old. It was oxidized and cross-linked and was no longer soluble in solvents such as naphtha or turpentine which would originally have thinned it. It was not even visibly affected by acetone or ethyl alcohol, solvents which act strongly on young oil paint. Yet it was very slightly soluble in xylene, a relatively mild solvent for aged oil paint. This was an encouraging finding.

In addition to the solvent testing, an x-radiograph was taken of the central area of the painting including the Madonna. It revealed flake losses in the same pattern as appeared in the 1930 photograph. This too was encouraging because it suggested that the photograph could be taken as representative of the state of the painting under the obscuring overpaint. At least no further flake losses had occurred since the photo was taken. The x-radiograph, unfortunately, could not show whether the original surface had been damaged by harsh cleaning, referred to by conservators as solvent abrasion.

Finally, a number of tiny paint cross-sections the size of the head of a pin or smaller were taken with a sharp scalpel from the edges of existing cracks, embedded in plastic and examined at 400 x magnification, to help in determining the layer structure of the original painting and the later additions. These revealed that the canvas had first been covered with a white chalk ground layer followed by a layer of dark red paint or “imprimatura.” The design layer was executed on top of this red layer. Many, though not all, of the cross-sections also showed a layer of varnish on top of the original paint beneath the overpaint. This was very good news because the varnish could work as an isolating layer protecting the original if a solvent system could be found which would dissolve the overpaint without removing the varnish layer. Alternatively, the varnish might dissolve more readily than the overpaint, thus undercutting it and helping to release it from the original paint.

The combined information derived from the solvent tests, the x-radiograph, and the cross-sections, although not a complete picture, was encouraging enough that it was decided to proceed with treatment to recover the original painting from the crude later paint. (Further treatment, not described in this article, was required to remove the lining fabric and adhesive from the reverse in order to flatten planar deformations in the original canvas and allow it to be securely mounted for display.)

A cleaning system was devised using xylene but putting it into a gel form so that it could be held against the surface longer without evaporating, giving it time to soften the overpaint. The gel system also helped to limit penetration of the solvent through cracks and thus minimize contact with the original paint. It was brushed on in small areas at a time, several inches square, following design forms. It was allowed to remain for up to one minute, then cleared away with a dry cotton swab taking dissolved overpaint with it. The surface was further cleared with small swabs dipped in pure xylene. This process was repeated until the original surface was revealed, usually two to four times. The initial results were both satisfying, because the original painting being revealed was of so much higher quality than the crude repainting, and discouraging, because there proved to be an unanticipated complication.

Under the main layer of overpaint were thick smears of different colored paint applied like putty over all the areas of flake loss and other damages. These “putties” were of all different colors, including gray, green, red, blue and yellow, with no attempt to match the surrounding original paint. They covered much intact original paint as well as damage, were widely scattered over the surface, and were very disfiguring. They were not dissolved by the xylene gel as the overall overpaint was. Instead they could be softened with the gel to a point where they could be carefully scraped off using a scalpel working under magnification. This was successful at removing most of this different type of overpaint, but was extremely time-consuming.

Yet, as the overpaint slowly disappeared over a period of five months, the results were very gratifying. Hidden details such as the rays of light emanating from the Madonna’s head and the stars around her crown, central to the iconography of the painting, were revealed. The crude draperies covering the naked putti holding the crown came off as did the overpaint which had obscured God’s extended left arm. God’s face, although damaged, was revealed to be much grander, and the top edge was found not to be as truncated as had been feared from looking at the 1930 photograph. (The edges had been covered by the frame, nailed through the front surface of the painting.) Mistakes in drawing by the restorer, such as combining the bottom of the Madonna’s robe with the knee of the kneeling angel were erased revealing anatomy that made much more sense. Mena’s colors and brushwork are much more subtle and skilled than what had been visible.

The cleaned surface revealed major damage, as expected. Besides the flake losses, much solvent abrasion was found. This can now be understood as explaining the smeary look in the 1930 photograph. It must have occurred while the painting was framed as in the photo, because the edges covered by the frame are not damaged in the same way. Yet the painting is essentially intact.

The final phase of treatment (not yet begun as this article is being written) will be to carefully inpaint the most disfiguring losses to match surrounding original paint. The inpainting will not cover intact original work as was done before. It will be done in a stable medium which will remain readily soluble in a very mild solvent which does not affect the original. Unlike the long and tedious process required to remove the overpaint, described above, the new inpainting will be removable in minutes should this be desired. It will be kept to a minimum, not attempting to make the painting look new, but merely restoring the unity of the surface so that the damages are not distracting and the viewer can appreciate both the meaning of the image of the Madonna of Light as Luis Mena intended and the extraordinary history of the painting.

Elizabeth Court has a B.F.A. in art history from Virginia Commonwealth University and a M.S. degree in art conservation from the University of Delaware/Winterthur Museum. She earned a diploma from the Hamilton Kerr Institute, University of Cambridge and is a Fellow of the American Institute of Conservation of Historic and Artistic Works. Ms. Court joined the staff of the Balboa Art Conservation Center in 1981 and has been Chief Conservator of Paintings since 1984.