The examination & conservation of the Raphael cartoons
An important aspect of the refurbishment of the Raphael Gallery in the 1990s was the opportunity it provided for close examination of the cartoons. The following explains some of the techniques used in the examination of the cartoons. It also highlights some of the precautions taken to ensure the safety and conservation of the cartoons.
Figure 1. Opening of the false walls
In 1992 work began on the refurbishment of the Raphael Gallery. One of the first tasks was to do an initial condition check and to decide how and where the cartoons should be relocated during the building work. Figure 1 shows one of the cartoons, in its frame, being winched out from the false wall in the old gallery.
Figure 2. Moving the cartoons to temporary storage
The recurring problem posed by the handling of the cartoons throughout their history is their large size. Just to move one cartoon a few metres involved careful planning and a team of highly trained object handlers. Figure 2 shows one of the cartoons out of its 18th century gilt frame but fixed into a travelling frame to help reduce vibrations during movement through the museum to a place of temporary storage.
Figure 3. One of the cartoons on the metal easel
The only space large enough, in which to carry out the examination and conservation of the cartoons was the gallery itself. Once the refurbishment was completed the work on the cartoons could begin. Figure 3 shows one of the cartoons on a specially designed metal easel which could be fixed at various angles from horizontal to vertical.
Figure 4. Set-up for transmitted light photography
Various examination techniques were used on the cartoons to gain as much information as possible about their condition and their original construction. We think the cartoons were cut up into strips as part of the weaving process in the 16th century and these strips were reassembled onto canvas at the end of the 17th century. This canvas backing makes it difficult to see just how Raphael and his assistants would have made the cartoons. Transmitted light photography allowed us to 'see through' the cartoons.
Figure 5. Photograph of the cartoon Death of Ananias in transmitted light
The image is somewhat complicated by the presence of the stretcher bars and the cross bars of the metal easel. However a quite regular pattern of overlapping sheets of paper can be seen indicating that the original construction consisted of one layer of paper. Paper patches - repairs from the 17th century - can also be seen as well as vertical lines of lights which correspond to where the cartoons were cut up into strips. The bright dots of light correspond, in part, to pin holes which date from the 19th century practice of pining tracing paper to the cartoons for copying purposes.
Figure 6. Raking light photography
This image was taken using strongly directional light from one side only. This technique highlights creases, tears and distortions allowing better documentation of condition.
Figure 7. Diagram showing the position of the canvas strips
Raking light photography also revealed the presence of a 'bump' on either side of where the cartoon had been cut into strips. (This can be seen in Figure 6). Closer examination confirms that these 'bumps' correspond to strips of canvas applied to the back of the edges of each strip of cartoon. They were probably applied in the 17th century so that the individual cartoon strips could be pinned up together for display and for copying.
Figure 8. Infra red reflectography
Infra red reflectography was used to reveal the underdrawing. Infra red can pass through some paint layers before it is reflected by the charcoal underdrawing making it much easier to see. In Figure 8 an alteration to the position of the thumb of the hand of Christ from the cartoon The Miraculous Draught of Fishes (see Figure 11) can be seen. Infra red also revealed that Raphael, surprisingly, did not use any squaring up lines to facilitate the underdrawing. He appears to have worked freehand directly onto the paper.
Figure 9. X-Radiography
A limited number of x-rays were taken during the previous conservation campaign in the 1960s. The 1990s project used x-rays more extensively - the whole of two cartoons were x-rayed and the main features of all the others. The x-rays highlight the original lead white paint layer used by Raphael and his studio assistants. Later retouchings in other media, such as pastel, are transparent to x-rays and hence do not show up. As in this x-ray of the head of Christ from the cartoon The Miraculous Draught of Fishes much clearer picture of the condition of the painting can be obtained. A comparison of the 1990s x-rays with those taken in the 1960s shows any changes in condition.
Figure 10. Photogrammetry
Part of the 1990s research looked at the paper used by Raphael. To do this it was useful to have a record of the size of each individual sheet of paper and how these sheets were stuck together to form the cartoons. To measure each sheet and each overlap by hand would have been very time consuming and somewhat risky for the cartoons. Instead we employed a technique known as photogrammetry, which is commonly used for taking accurate measurements of buildings. It involves taking stereoscopic photographs at known reference points. This information is then fed into a computer to give a detailed print out. As well as giving accurate measurements of the sheets of paper the process also makes it easier to document the size of any creases, tears and other distortions. In theory these measurements could be repeated in the future to monitor any changes.
Figure 11. Pigment Analysis
Some limited pigment analysis was carried out on the cartoons. This was done particularly in areas of the cartoons that appeared to have changed colour. One of the main colours used by Raphael was red madder lake either on its own or in combination with other pigments - particularly with blues to give purple. Unfortunately madder lake is very susceptible to fading causing changes to the original appearance of the cartoons. A well known example of this is the cloak of Christ in The Miraculous Draught of Fishes which now appears white although the reflection is red. Analysis showed that the cloak had been painted in red madder lake - now faded - but the reflection was painted using the more stable pigment, vermilion.
Figure 12. Conservation
As designs for tapestry the cartoons were used as working drawings and suffered a lot of damage in the past. More damage almost certainly occurred when the cartoon strips were laid down onto canvas at the end of the 17th century. Despite this the cartoons are now relatively stable. However some conservation work was carried out. Loose areas of paper were reattached using the inert adhesive, methyl cellulose. Also the edges of the cartoons were consolidated using strips of Japanese paper and wheat starch paste. More interventive treatment would have been risky for the object and may, in this case, have resulted in the loss of forensic information of use to future researchers.
Figure 13. Hanging the cartoons
The cartoons are now hung directly onto the walls of the gallery rather than in false walls as previously. A new system was devised that allowed the cartoons, on their stretchers, to be secured into position independently of the frames. Because of their size and weight the separate hanging of cartoon and frame was a safer option both for the cartoon and for the people handling them. This process involved large amounts of equipment and many people. A laser light was used to help line up the cartoon before the frame was positioned. Data loggers placed inside two of the frames monitor any changes in environmental conditions.
The Museum wishes to thank Agfa-Gevaert Ltd for the gift of the X-ray film used in the examination and for making this display possible.