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Before & After Gallery

Conservation Treatment of Sussex Pastoral

Painting Before Treatment
Painting After Treatment
Painting Before Treatment
Painting After Treatment


This egg tempera painting is executed on canvas adhered to a wooden panel. The panel had cracked in several places and the painting had innumerable small losses of paint over its entire surface. Analysis revealed that the ground layer (just underneath the paint) contained very little binder (adhesive) to hold it together. This problem of flaking paint had recurred a number of times over the years, despite local consolidation treatments and would continue unless an appropriate solution were found. The painting was therefore sent to the Canadian Conservation Institute for examination and treatment.

After a good deal of experimentation it was decided to infuse the entire surface of the painting with paraffin wax that would, in fact, become the binder and hold the paint and upper ground layers together. This procedure was carried out with the aid of carefully placed heat lamps. To prevent possible heat damage during this process, the temperature at the surface of the painting was carefully monitored and maintained at a level just sufficient to melt the paraffin and permit it to penetrate into the paint and ground layers.

Once consolidation was complete, the small paint losses were inpainted and a clear protective coating applied to the entire paint surface.

Because of the particular problems associated with this painting (i.e. flaking paint and splits in the wooden panel auxiliary support), it was decided to enclose the painting in a sealed frame capable of minimizing fluctuations in relative humidity (RH). Thus a "box" of conditioned silica gel was incorporated and sealed into the frame behind the painting. Silica gel is an inert, non-toxic and chemically stable form of silica which, when properly conditioned, is capable of absorbing and releasing water vapour from and to its surroundings to maintain a uniform RH level within these surroundings. A hygrometer-thermometer was incorporated into the bottom of the frame to allow quick and easy monitoring of environmental conditions within the enclosed frame.

Figure 1
Figure 1. Painting before treatment: Numerous vertical splits and deformations in the wooden panel support are emphasized in this raking light photograph. Less visible are the numerous small losses of paint caused by insufficient binder within the upper layer of the ground.

Figure 2
Figure 2. Painting after treatment: Because of the sensitive nature of its composite materials, the painting is enclosed in a special frame incorporating a chamber containing silica gel. This material has the capacity to absorb and release water vapour, thus maintaining a near-constant RH within the enclosed environment surrounding the painting. (The two vertical lines near the bottom right corner are reflection off the glass surface.)



Figure 3
Figure 3. Overall consolidation of the painting was achieved with paraffin wax melted onto the surface of the painting by means of infrared heat lamps. The molten wax penetrated into the paint and ground layers to bind them to one another and prevent further flaking.

 

Figure 4
Figure 4. Missing design elements (areas where the paint has flaked away) were inpainted with watercolour paints. This particular medium was chosen because it adheres well to the surface of the painting, is easily reversible and maintains the matte finish on the surface of the painting.

 

Figure 5
Figure 5. In order to create a well-sealed environment for the painting, the inside surfaces of the frame were covered with a moisture barrier material called Marvelseal 360. This thin foil composed of nylon, aluminum, and polyethylene was heat-set with a tacking iron.

 

Figure 6
Figure 6. The principal part of the silica gel box consists of acrylic egg crate material, the gel being held in the tiny compartments created by the egg crate grid.

Diagram
The diagram above shows the various materials used in the construction of the sealed frame which now holds the painting.

 

Figure 7
Figure 7. The materials used to construct the box that holds the silica gel are shown unassembled. The side next to the painting is covered with matboard to permit the transfer of water vapour to and from the environment surrounding the painting. A sheet of plywood sealed with Marvelseal 360 forms the reverse surface of the box.

 

Figure 8
Figure 8. The reverse of the sealed frame assembled with the painting inside is shown above. The box containing the silica gel is secured to the reverse edges of the frame with brass mending plates.
Figure 9
Figure 9. In order to monitor the RH within the sealed frame, a small dial thermo-hygrometer was attached to the inside surface of the bottom of the frame.
Figure 10
Figure 10. A tiny window cut into the bottom of the frame was sealed with a block of Plexiglas to permit viewing of the thermo-hygrometer. If the RH inside the sealed frame varies from the accepted norms, the silica gel can be reconditioned through the addition or removal of moisture as appropriate.

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