Case Study    
  "Portrait of Adolf Hitler"
by Heinrich Knirr

Before Treatment
August 10, 2004
Numerous small losses were weak and unstable consistently exposing raw canvas. All of these areas had to be individually stabilized using a 1:10 gelatin adhesive. The liquid adhesive was applied warm using a small sable brush. This initial step allowed treatment work to continue without risk of further loss.
The cleaning of an oil painting involves the removal of discolored surface films and all areas of non-original paint. A precise understanding of the chemistry of paint films is required to remove the films without injury to the paint layer. The work is carried out under binocular magnification using appropriate conservation solvents. The surface was coated with a thin dirt and grime film. This layer was flattening the three-dimensional character of the portrait and imparting an overall graying effect. Dirt films are particularly difficult to remove for the dirt often becomes embedded into the drying paint layer. Small cotton swabs were used to remove the overlaying film. The painting was cleaned using a mild Ph-neutral detergent solvent.

Detail Horizon During Cleaning

Detail Horizon During Cleaning

Upper Sky During Cleaning

Dirt Square

Forehead During Cleaning

Detail Forehead During Cleaning
The paint layer showed numerous losses. Harsh canvas waves and deformations resulted in pervasive surface cracks. The edge of the canvas folded around the side of the stretcher is referred to as the tacking-edge. From numerous restretchings and the weight of the canvas this edge no longer provided adequate support. In order to provide future stability a new Belgian linen strip was attached to the original edge using a reversible conservation PVA adhesive. When completed, the painting was returned to the original stretcher using copper tacks.

Tacking Edge--Face Down

New Belgian Linen Attached to Edge
Before varnishing, all of the former losses were filled with gesso. Filling has two purposes. It prevents further damage by sealing the edges of holes, cavities and open cracks. It also is used to reproduce a sympathetic surface with respect to plane and texture. The gesso was a mixture of marble dust and a 1:7 gelatine adhesive. Each loss was carefully filled and smoothed to plane. The upper canvas tear was filled similarly.

Gesso Fills

Gesso Fills
A brush coat of Windsor-Newton non-yellowing varnish was applied to the paint surface. Varnish is applied for several reasons. First, it reinstates the richness of the paint allowing the darks to have their proper tone. This re-creates the intended three-dimensional illusion of space. Secondly, it keeps dirt and air pollution off of the picture surface. Third, the surface coating assists to protect the paint layer from damage caused by abrasion, moisture and accidental accretions. The varnish also creates an ethical buffer between the original paint layer and the retouching or inpainting. Conservators do not paint directly on the original paint surface. The work is done on top of the isolating varnish and can be removed by simply removing the underlying varnish.
Retouching is carried out to correct visual irregularities caused by inherent structural problems or surface damage. Its purpose is to reduce or eliminate these inconsistencies. The retouching was completed using Maimeri conservation pigments. These pigments are both color and light fast offering confidence that the restoration areas will remain consistent over time. Also, the pigments are soluble in mineral spirits. This relatively weak solvent permits safe removal without risk of injury to the paint surface.(8)
November 10, 2004
After retouching, the application of a final non-yellowing spray varnish completed the treatment.

Before Treatment

After treatment
Knirr 1938 
(8) Filling, retouching and varnishing purposes based on Morton C. Bradley's "The Treatment of Pictures."1950 Cosmos Press. Cambridge, MA. The author wishes to thank Mr. Bradley for his support and influence from 1972 to 2004.
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