Conservation Treatment:
Auxiliary Support:
- the stabilizing hardboard was removed from the reverse of the painting
- a new frame was to be made for the painting that would accommodated its present format, therefore the top of the auxiliary support was rounded from the height of about 50 cm. This caused an overhang of c. 1 to 2 cm.
- at the top edge the missing section was reconstructed with material from the removed panel: the sections were butt-joined and a wooden veneer (2 cm thick) was adhered to the reverse (with PVAC glue (Ponal)) as carpenters glue would not have provided the required stability considering the relatively small area of adhesion.
- the canvas was attached by reactivating (with heat/iron) what wax-resin adhesive was left, and where necessary new wax was added.
- an 8 mm plywood board was fitted in the new frame to provide addition support for the painting. It was then fixed in the frame with wooden battens that were screwed into the frame. The rebate was lined with polyester felt to cushion the contact surface.
Surface cleaning:
- the reverse was surface cleaned with a Hoover
- surface cleaning of the paint layers (slightly damp cloth/sponge or swab)
- removal of the dark dirty incrustations in the beige background of 'The Last Supper' was done mechanically with a scalpel, and the area was then cleaned with slightly damp swab.
- mechanical removal (scalpel) of a glossy varnish drip as well as crusty spots and displaced paint flakes (from the maroflage)
- removal of partial incrustations of dirt on the green curtain: repeatedly softened with a moisture treatment and then removed in discrete layers with drying periods in between
After the surface cleaning a whitish film was evident in some areas and was probably caused by remnants of a surface coating or varnish that has begun to degrade.
- regeneration of these areas by rolling an acetone swab over them once
Removal of the remnants of overpaint from the uncovered lower section of God the Father's coat
- softened with acetic acid (25%ig) (following the method recorded in the examination report from 1959 to 1965), subsequently mechanically removed with a scalpel, repeated treatment of an area with drying periods in between; in some sections DMSO achieved the same degree of softness
The removal was very laborious and time consuming, particularly in areas where the original paint layers beneath the overpaint are very damaged. Here, because the original was so damage the adhesion of the overpaint to the support is much greater.
The dark green final glaze belonging to the overpaint was removed first and then the compact grey layer.
Restoration Treatment:
Filling of losses in the paint layers
Only the large, obtrusive losses around the tears and holes were to be filled. In the sections where inserts were already present the fill material was to be applied like a ground, exploiting the canvas beneath to achieve the desired surface texture.
- first the two inserts with incorrect thread counts were replaced
- the losses were sized with rabbit skin glue (70:1000)
- deeper losses were filled with a chalk paste (champagne chalk/animal skin glue 70:1000, pigmented slightly with yellow)
- the shallow losses were filled with a liquid chalk ground (champagne chalk/animal skin glue 70:1000, pigmented slightly with yellow)
- finally the surface was wet sanded flush with the surrounding area
- an isolating layer of shellac was applied to the fills
Retouching:
Concept:
The extent and the type of retouching as well as the use of different media were decided in situ on the 28.04.2015 together with Fr. Dr. Danz and Herrn Pfarrer Lindemann (representing the owner). The retouches were generally to be glazed, and in the area of the curtain an aqua-sporca method was to be employed. It thus remains possible to recognize the fragmentary and damaged state of the painting, while achieving the optical reintegration of isolated areas. Losses in the overpainted sections of the curtain where original paint is visible were not to be retouched.
Method and execution:
- 'The Eucharist' (Overpaint, Beck 1853): water colours, in the pale background, mixed with white tempera paint to achieve the pale tones
- green curtain: lean Mussini-oil/resin paint with oil of turpentine as diluent, gloss adjusted with dammar in turpentine (1:8)
- the figures of Wolfgang and Joachim (preserved original paint): application of a thin dammar varnish (1:8) to saturate the predominantly dark area; retouched with Mussini-oil/resin paints using turpentine as a diluent
- the uncovered original sections (red coat, background): lean Mussini- oil/resin paint using turpentine as a diluent; the gloss was adjusted with dammar in turpentine (1:8)
Once the painting was framed it became apparent that a strip of the backboard (c. max. 2 cm in width) was exposed at the left and right sides where the rounded top begins. This area was also retouched with lean Mussini-oil/resin using turpentine as a diluent.
Conclusion:
An optical reintegration of the disfiguring sections was achieved. However as already suggested by Frau S. Hönig in her Conservation concept it would be helpful for the viewer (particularly for the final display situation in the St. Bartholomäi-Kirche) if a explanatory text were available. The painting has a documentary character and exemplary historical validity due to its present condition.
New insight with regards the history of the object:
The overpaint on the Holy Trinity:
In the second half of this chapter written sources are listed that indirectly suggest a change in the painting's appearance:
1. 1596 - the painting of the Holy Trinity was eliminated and replaced by a cloud
2. 1662 - the baptism of Christ should be removed or concealed
3. 1699 - the sarcophagus painting was touched up and recorded in the town chronicle of 1758-1823 as being among the paintings located there
The period between 1596 and 1699 can be considered as the possible time span in which the Holy Trinity was overpainted. However the ageing and condition of the paint layers as well as the observations made during the removal of areas of overpaint do not allow a more precise dating, as no significant changes occurred in painting techniques during that period. The degree of ageing is typical for both the 16th and 17th centuries. It can however be excluded that a cloud was painted beneath the overpainted curtain. Removal of remnants of overpaint at the right beside the figure of Wolfgang began with a final dark green glaze. The layer beneath this revealed an arrangement of folds executed in white and grey. This undermodelling would have been completed with the application of the afore mentioned glaze and would have shimmered through (as can be observed in other areas of the painting). It is a very compact layer and was applied directly over the original paint surface.
The overpaint on the Eucharist:
It is certain that the painting was reworked in 1853 by the court painter Beck. The depiction of 'The Eucharist' attributed to him was executed on a pale, relatively thick isolating ground that was applied to the area between the two sides of the curtain and the donor figures before it was reworked. The paint application here is quite different from the rest of the picture; the surface appears more matt and was probably executed employing a certain amount of tempera medium (during the surfacing cleaning it appeared sensitive to moisture). Along cracks and in areas where the paint layers have separated the underlying dark curtain is visible. Cleaned areas mentioned by Beck were not found, but are (if they were present) covered by the ground layer. My observations here correspond with those of Frau Hönig.
Observations concerning the cleaned area at the bottom:
Dark shadows could be discerned in the exposed zone along the lower edge beneath 'The Eucharist' by Beck after surface cleaning. These could not be reconciled with the representation of Christ's foot now visible. They may represent shadows caused by the binding medium of another paint layer. However this phenomenon cannot be determined with absolute certainty.
