Recovery of an exceptionnal piece

The museum is restoring an exceptional work: an immense picture of 3.40 m x 3.80 m, dating back to the 16th century and featuring the martyrdom of St. Paul

An enormous paper fresco, this piece encompasses the vitality and worries of an age in complete transformation: the Renaissance. Attributed to Pieter Coecke, a great Flemish master, this artist is relatively unknown these days yet was one of the great painters of his era. 

This priceless "tapestry cartoon" is a rare example to have survived the passage of time. In practical terms, this large scale depiction was used as a template for generations of weavers for the realisation of their tapestries.

As a commentary to this process, an exhibition invites the public to explore the artistic and historic world of this exceptional piece. 

Stages of an exceptional project

1. Status Report

A photographic campaign and visual appraisal have provided considerable information on how the work was produced and what its current status is : the cartoon comprises 61 strips of paper, and was first sketched then painted with distemper*. It was reinforced on the back with pieces of paper, and then pasted on canvas in the 19th century. This no longer provides sufficient support to the work and a great many distortions on the surface are causing rips and material loss. The painted layer is cracking, in particular on the zones which have been overpainted*.

1. Removal of the glass panels, analyses and dust removal

A restoration workshop has been set up in the heart of the City Museum for the next eighteen months.

The protective glass panels are removed and the cartoon attached to a temporary framework. Microscopic samples of materials taken from the cartoon are analysed to guide the restorers in their choice of treatment and enhance their understanding of the production process and how the work was used.

Ventilation is used to remove the dust from the back of the cartoon. A support is placed right against the canvas during this process, which is carried out using a soft brush or perhaps an eraser.

2. Consolidation

The first consolidation phase will take place on the front of the work to avoid loss of material while it is wound up and transported to the workshop. These supports will also prepare the surface at the back for future stages of the work. These are made of crépeline de soie applied to particular areas of the cartoon surface using a polysaccharide mucilage from seaweed (funori). These two materials have been chosen as they do not affect the final appearance of the painted layer and permit the whole process to be reversed.

3. Transport

The monumental size of the cartoon precludes it being mounted on its framework. It will be transported to the restoration workshop set up on the second floor via the staircase, wound round a 60 cm diameter, 4m long cylinder, which has taken the fragility of the cartoon, the Museum's logistic constraints and human means fully into account.

A soft protective material has been placed on the front of the cartoon as well as a layer of polyester wadding to stop the paper deformities to be crushed. A would-be cage has been put round the cylinder to protect it and allow it to be gripped onto while it is being transported vertically up the staircase.

The roll will then be placed on the work surface.

Transport cardboard on the 2nd floor of the museum

4. Removal of the cartoon's old consolidation support

The work, wound round the cylinder, is placed on the work surface. It will be unwound gradually as the restoration work progresses, giving access to the back and enabling the restorers to remove the canvas and then the various consolidation strips by simple traction, by means of a humidifier device and heat  diffuser placed at the front of the work.

The paper immediately under the canvas was pasted on in the 19th century and covers the entire front surface.  Its removal will enable older consolidation methods applied to the work while it was being used for the manufacture of tapestries, to be seen. 

The rips and gaps will be consolidated as the canvas is gradually unwound, using fine strips of Japanese paper* and wheat starch paste.

5. Cleaning the paper, lining and stretching the sheets

Once the tears have been repositioned and consolidated, the work is subject to three successive stages to reinforce its paper support: each sheet of the work is lined on the back in its entirety with Japanese paper combining fineness, flexibility and stability.
The sheets are then assembled in several groups following the original joins then each group of sheets is lined with another flexible Japanese paper which is slightly thicker than the previous one.
A third reinforcement, similar to the first is carried out. All the lining stages are performed using wheat starch paste. Each stage may be followed by a slight tensioning of the sections of the work which is designed to reduce deformations in the paper accumulated over the years.

By separating all the sheets the deformations in the paper were able to be reduced. This tensioning stage was therefore no longer necessary.

6. Backing

The work must be stuck to a support, a linen canvas, to ensure its proper preservation and allow it to be exhibited. This must be prepared to stabilise the behaviour of the complex "canvas/paper" support during hygrometric changes in the atmosphere (the canvas and the paper do not react to humidity in the same way which therefore risks damaging the work). This action reduces and slows down the deformation of the canvas over time. It strengthens its plastic character which is essential for a good, long preservation of the work.
The canvas is "decatized" to reduce the crimp of the yarn and remove the finish: the canvas is washed and brushed while it is stretched over a working frame. Once dry, the canvas is relaxed. A massage further stretches the threads then a second decatizing is performed. The canvas is stretched then glued using wheat starch paste. Two layers of Japanese paper are glued to the canvas to absorb its relief and provide a barrier to dust.

Marouflage of the work onto the prepared canvas
The different groups of sheets are assembled for the marouflage.
This must be carried out with dexterity, precision and care in order to keep the bonding power of the wheat paste and carefully manipulate the large areas of wet paper.

Before pasting, all the pieces are laid out on the canvas in order to mark the position of each one. Each part is then wet between the felts. The wheat paste is prepared and the marouflage support is moistened with spray. Paste is put onto each piece and at the same time onto the corresponding area of the marouflage support. This piece is applied to the support. The second large piece is then treated in the same way and laid as precisely as possible in relation to the first piece.
To finish, certain later pieces (from the 17th and 19th century) are laid in turn.

7. Preparation of coloured sheets to fill in gaps

8. Integration and retouching

This stage, very tricky from an ethical point of view, will give the work back its harmony and a coherence that it has lost over the centuries. Every intervention is discussed at length with the Scientific Committee.

The integrations of gaps prior to the 19th century marouflage, the colour of which matches the coloured environment are replaced through the back or the front of the work. The large integrations painted on the paper used for the 19th century marouflage are re-integrated into the work. The choice of overpaints to be reduced or removed is then identified on the photo of each sheet making up the work. This focuses mainly on overpaints masking alterations in the paper (tears, creases, wear and tear, stains, excess beyond the gaps).

Overpaints that are designed to modify the drawing's composition are left untouched with the exception of the horizon, lowered following a large alteration to the upper left part of the cartoon. Removal is performed using magnifying glasses and scalpels, dry then with a little moisture. The gaps are filled with a handmade western paper made from linen rags and glued with gelatine. This paper is tempera-coloured before the integration of the gaps. The integration colour is then adjusted with watercolour and coloured pencils.

9. Transport and hanging of the cartoon