ON THE CONSERVATION AND RESTORATION OF LUCAS CRANACH´S "ALTARPIECE OF THE HOLY KINSHIP´
The central panel of this triptych consists of six cross-glued limewood boards whose grains run horizontally. Within the framework of an earlier restoration, these boards had been substantially reduced in thickness and glued to a beechwood backing. Together, the original limewood panel and the backing added later are a mere
6 mm thick. The back side of the backing was accordingly furnished with wooden parquet to lend it stability.
The limewood panel exhibits traces of infestation with vermin; moreover, in the transfer process a strip some 4 cm in width had been lost. This missing section of the original wooden panel extends across the entire width in the area of Madonna figure’s knee, and had been replaced by a narrow wooden board during the transfer process. The ground and painting had been supplemented in this area. The central panel had been trimmed slightly along the top edge.
The ground and painting on the front of the central panel had been gravely adversely affected by the above-described measures. Along with the 4-cm-wide strip of wood, later replaced, all of the original paint on that strip had also been lost. Executed in oil, the supplementary painting later undertaken had changed in colour significantly with age and was visible as a discoloured strip across the painted surface. A number of further flaws in the painting had been caused by wood pests and the warping of the backing layer due to climatic fluctuations. These areas had likewise been retouched in oil and were meanwhile severely discoloured. Especially in the areas depicting flesh, glazes applied to the composition to indicate shaded areas had been badly damaged by the use of inordinately aggressive solvents to clean them during an earlier restoration.
In a number of areas, the adhesion between the painted layer, the ground and the panel was no longer stable; particles of paint had begun to detach themselves from the background. During past restorations, an uneven and meanwhile slightly yellowed coat of natural resin varnish had been applied.
Central panel after cleaning and before retouching
Following the stabilization of the loosened areas of ground and paint, all layers of varnish and all oil retouching previously carried out as restoration measures were removed; the only non-original painting retained was that on the abovementioned strip. Over a newly applied, thin coat of natural resin varnish, the flaws in the limewood panel, the ground and the paint were puttied and retouched.
The damages on the two wings of the altarpiece proved less severe. Due to the fact that they were painted on both sides, they were not furnished with a second wooden backing, and thus differ in this respect from the central panel of the triptych. Substantial losses and damages to the painted layer were nevertheless ascertained on the wings as well, brought about by the construction of the panels, climatic fluctuations and crudely implemented cleaning measures.
Like the central panel, the altarpiece wings also consist of several individual, cross-glued boards, although this was an unusual choice of constructions for a vertical format. Climatic fluctuations had caused shrinkage and swelling of the wood, leading in turn to changes and flaws in the layer of paint. Initially, long horizontal craquelures had formed, on which the edges of the flakes of paint stood out. In these areas, the paint had been rubbed off down to the ground by aggressive solvents and mechanical stress during past cleaning treatments. It had thus been possible for water to penetrate the layers during later cleaning measures, causing the ground to swell and, in many places, dissolve. As a consequence, narrow horizontal rifts had formed in the painted layer in a number of places. These damages were most prevalent in areas in the lower third of the panels, where the quality of the boards is apparently poorer. On the front sides, the flesh zones of the persons depicted were particularly affected by this problem, i.e. areas exhibiting lighter shades which were subjected to more thorough cleaning.
Left wing, Mary of Cleophas, detail of face after removing overpaint
In order to conceal the damages which had occurred, putties had frequently been applied in a crude manner during various past restoration phases, in many cases extending far beyond the original painting surface and further exacerbating the wave-like distortions of that surface. The panels had moreover been generously retouched in a number of places which had since become badly discoloured, severely compromising the quality and effect of the painting. For this reason it was decided that, following the necessary conservation measures, old retouching and overpainting would be removed and the putty be reduced in the areas where it covered original paint. The remaining retouched/overpainted areas could then be chromatically adjusted to correspond to the original. Moreover, with the aid of cautious retouching, the flaws in the paint layer could be reintegrated into the original painting.
Left wing, Mary of Cleophas after removing old varnish and overpaint
Following the completion of the restoration, the central panel and the inner sides of the wings exhibit a uniform pictorial aesthetic despite the fact that their state of preservation varies greatly.