Conservation of Paintings by Nguyen Trong Kiem

As a result of severe environmental conditions and poor storage during the war, poor condition is characteristic of many paintings in Vietnam, and many are in urgent need of conservation.

As part of a research project instigated with Northumbria University, Newcastle upon Tyne, two paintings by Nguyễn Trọng Kiệm (1933-1991) were sent to undergo scientific analysis and conservation treatment. Both Portrait of my Wife and Portrait of a Student (Figures 1 and 2) were painted in 1963 in Hanoi. Their analysis and treatment revealed the complex nature of their deterioration, as well as conservation approaches for such paintings.

The paintings remained in the possession of the artist’s family until their recent acquisition by Witness Collection, an important collection of modern and contemporary Vietnamese art.

Figure 1: Portrait of my Wife by Nguyễn Trọng Kiệm

The painting Portrait of My Wife (Figure 1) contains areas of thinly applied oil paint, as well as areas of thick, textured paint. The thinly-painted areas were flaking, while the impasto was lifting off the ground. Small round white particles were observed within the impasto, and in many places, the paint had broken away from these particles.  A thick layer of dirt gave the painting a dull appearance. A granular surface deposit was also identified.

Figure 2: Portrait of a Student by Nguyễn Trọng Kiệm

The painting Portrait of a Student (Figure 2) consists of  thinly applied oil-based paint, and is very matte in appearance. The majority of the painting was repainted by the artist after significant paint loss had already occurred. The paint was flaking extensively, and blind cleavage was present in many areas. In addition, severe tenting of the paint layers had occurred . The painting was unvarnished, with a layer of efflorescence on the surface.

Scientific investigations sought to illuminate the materials, techniques and degradation mechanisms in the paintings.

Based on results of media analysis, the ground in both paintings was determined to contain a drying oil and a proteinaceous medium, while linseed oil was used in the paint. zinc carboxylate soaps were identified through FTIR analysis. A thin media layer on top of the ground in both paintings was identified as collagen-based glue. A similar animal glue layer was also identified between the original paint and overpaint on the painting Portrait of a Student. Swelling and weakening of this hygroscopic material during periods of high humidity could have exacerbated flaking of the paint layers.

Samples taken from both paintings were examined by polarized light microscopy (PLM) and scanning electron microscopy coupled with energy dispersive x-ray analysis (SEM-EDX). The ground of both paintings, as well as artist’s overpaint was found to consist of lithopone. This correlated with fluorescence of overpaint when viewed in ultraviolet (UV) light. Zinc oxide was the main pigment component of the paint, being extensively present in almost all layers for both paintings.

Zinc sulphate was found throughout the paint films, indicating the paintings had been affected by atmospheric sulphur dioxide pollution. Efflorescence on both paintings was identified by SEM-EDX as consisting of zinc sulphate crystals. In addition, free fatty acids and carboxylate soaps were present on both paintings’ surfaces.

The unusual circular inclusions found within the impasto layer of Portrait of My Wife were examined by SEM-EDX and were found to consist of masses of acicular zinc sulphate heptahydrate crystals. Because zinc sulphate is extremely water-soluble, it was foreseen that its pervasive presence could pose problems for conservation treatments involving aqueous methods.

Extensive testing of consolidants was undertaken, since consolidation would be the most important issue to address as part of the conservation treatment of the two paintings. Eventually, the only suitable consolidant was determined to be Aquazol, as it safely consolidated the paint without any unwanted effects. As a result, a solution of Aquazol was applied by brush to localised areas of flaking paint on both paintings.

In order for the raised paint on Portrait of a Student to be successfully consolidated, the canvas would have to be stretched. Expansion of the canvas would allow raised paint to once again be accommodated. This was achieved by paper stretching on a loom. This process was repeated several times until sufficient tension had been achieved, planar deformations were flattened and tented paint had begun to open up.

Figure 3: Treatment of tenting

A hot air blower was used to plasticise areas of tented paint prior to application of the consolidant. The consolidant was applied by brush, followed by further heating with the hot air blower. Once the paint was sufficiently flexible, it could be flattened without fracturing by ironing with a spatula. This process was repeated with gently increasing pressure from the spatula until the tented paint had relaxed down into plane. This technique allowed the majority of tented areas to be treated successfully (Figure 3). Once initial localised consolidation had secured the paint layers, the frame was turned over. Several coats of consolidant were brushed on to the verso and recto.

Surface dirt removal of the recto of both paintings was subsequently undertaken. Dirt removal led to a significant tonal lift, while also removing efflorescence and excess consolidant. Losses were filled using Aquazol with added whiting. After drying, a scalpel was used to recreate surface texture, while retouching reduced the visual impact of areas of loss. For this purpose, dry pigments bound in Aquazol were used.

The extensive use of zinc white in both paintings was found to be a significant factor in their severe state of deterioration, in combination with high humidity and atmospheric sulphur dioxide pollution in the Hanoi environment. Numerous unusual characteristics associated with the use of zinc white were observed. The formation of zinc sulphates within the paint layers affected treatment approaches, due to their water-soluble nature. Aquazol proved to be ideal for the consolidation of such matte water-sensitive paintings, and was subsequently used for filling and retouching of losses.