The extensive and detailed campaign of preliminary diagnostic investigations carried out on the occasion of the restoration (see Claudio Falcucci’s contribution in this volume on pages 149-167) made it possible to integrate the planning of the different phases in an informed and rigorous manner, allowing each decision to be calibrated on the basis of an exhaustive picture of the work’s constituent materials, their specific alteration processes, and the painting’s conservation history [fig. 1]. It is worth emphasising that the preliminary identification of the original materials, the techniques and also the earlier campaigns of restoration that have followed one another over the centuries (at least four, as we shall see), all barely legible to the naked eye under the irregular and heavily oxidised varnish, represented a fundamental tool for structuring the intervention in a clear and effective manner. Each stage of the work, which can be subdivided into three phases—cleaning, structural restoration, and aesthetic restoration—was documented in detail through a photographic campaign that enriched the available data as the work progressed, thus permitting a well-thought out plan for the work ahead, thanks also to the synergistic collaboration between the highly specialised professionals involved in the project.

Having determined the exact nature of the original materials, such as the type of canvas used as a support, the nature of the ground—that is the first “priming” lay- er applied directly onto the canvas—and the composition and particle size of each pigment present in the palette [figs. 2, 3], we then moved on to the analysis of data relating to the technique and execution of the work. Relevant aspects are the numerous incisions made by the artist in order to concisely position the composition in space, such as the incision that delineates the features of the face of the henchman to the right of Christ [fig. 4], the identification of the points of maximum light placed with decisive touches of lead white onto the preparatory sketch (the abbozzo), and the vibrant materiality of certain full-bodied brushstrokes used by the artist to mark a number of details of the composition [fig. 5]. Finally, the detailed analysis of the signs of wear, due both to the passage of time and to earlier restoration treatments, made it possible to establish the work’s general condition.

As can clearly be seen from the images of the painting in its state prior to restoration, it was obscured by many layers of a very uneven yellowed and oxidised varnish. The irregularity of the layers of varnish is the result of earlier cleaning treatments that were carried out preferentially on certain details of the composition, such as the faces and flesh tones, which were evidently considered to be of greater interest, while the darker passages or areas in shadow were deliberately left out and were therefore more obscured and less legible. The reading of the composition was thus altered in relation to its colour values and did not allow the clear interpretation of large sections of the painting.

Among the areas most transformed by the cleaning process, therefore, are the dark robe worn by the figure of Pilate, the deci- sive black brushstrokes of which marking the folds have now re-emerged, and that of the shoulder of the young henchman to the right of Christ, played out in tones of green earth marking the folds of his garment: both areas were illegible before the remov- al of the old varnishes. Other details that have re-emerged after the cleaning are the final strip of the red cloak on the far right, and the outermost thorns of Christ’s crown, which now radiate more sharply against the dark background. The course of the work undertaken was based on the principle of “minimal intervention”, that is we limited ourselves to the operations necessary for the work to recover the structural and aesthetic integrity required for safe conservation and easy legibility, but preserving, in an organic and functional manner, the aspects which were part of the object’s conservation history, with its stratifications and transformations. The following is a concise description of the three phases into which we divided the restoration work on the painting.

The Cleaning

We first proceeded to secure the paint film, consolidating the micro-areas of lifting paint that endangered the stability of the painted surface. We then moved on to carry out numerous solubility tests in order to identify the most suitable solvent for each area of the painting [fig. 6]. Once the desired results were obtained, a selective and gradual cleaning of the various areas was carried out, first removing the basic surface dirt and then thinning the different layers of varnish, which in some sections of the composition numbered as many as four, superimposed at different times.

For this particularly delicate phase, an electron microscope was also brought into use, in order to obtain—through patient and systematic work—an optimal differentiation of the times and methods of appliction of the solvents, which varied according to the different layers and requirements, in order to bring back to light for each area the original colours, whilst preserving the appropriate time-induced patina (as verifiable by ultraviolet examination).

Four different types of fills emerged after the removal of the old restorations [fig. 7], testifying to as many restorations over the years and, consequently, as many campaigns of varnishing and retouching of losses. The cleaning thus removed all the old restorations, from the most recent to the oldest, freeing the work from any past interpretative integration that inevitably compromised a correct reading of the painting.

Structural Restoration

Once the paint film had been secured by means of a facing, the old lining canvas was removed, as it was now unstable and no longer provided adequate support for the original canvas [fig. 8]. The proteinaceous glues from the old restoration were removed from the reverse of the painting using a scalpel, thus revealing the perimeter tension garlanding, clearly visible along at least three of the sides: these mark the point at which the canvas was folded around the original stretcher [fig. 9]. It can also be seen how the size of the painting was reduced for a time on the left-hand side and the original canvas folded onto a smaller stretcher, fortunately without causing any relevant loss of paint [fig. 10]. Subsequent restoration work, probably carried out during the twentieth-century, once again recovered the part of the canvas that had been folded over. It is therefore possible that the current measurements are the original ones, as the unpainted tacking-edge is also present on the left, but it is also possible that the absence of the tension garlanding suggests a slight reduction on that side.

Having repaired the losses and holes in the textile support by means of inlays of frayed canvas, in order to avoid any unevenness in the tensioning of the support, the original canvas was then re-lined onto a new canvas using an acrylic adhesive reactivated without the use of heat, and this was adhered to the reverse of the canvas using vacuum pressure. The structural restoration was concluded by re-tensioning the work onto a new two-way expanding oak stretcher with a central cross.

Aesthetic Restoration

After the removal of all the old repainting and fills as described above, the losses were filled in, that is the aesthetic reintegration of the damaged areas was carried out in a philological and precise manner thanks to new fills that were inserted imitating the adjacent surface, that is imitating the weave of the original canvas, and thus avoiding the annoying effects of light refraction caused by fills not coherent with their immediate context.

The first phase of the reintegration of the paint layer consisted in the application of a base colour tonally adjusted in watercolour, followed by retouching with varnish colours. None of the elements of the composition showed any extensive damage that required any interpretation and, therefore, it was decided to integrate with a mimetic, retouching in order to allow for an optimal reading of the work [figs. 11-14]. All the integration and retouching procedures are documented in detail in the photographic campaign and easily recognisable upon inspection under ultraviolet light. In conclusion, we would like to emphasise that in line with correct restoration practices, all materials and techniques used in the course of the work are fully reversible and compatible with the original.

This brief report and the extensive photographic and scientific documentation accompanying the restoration work, not only provide a detailed “medical record” of the painting’s condition, its conservation history, preservation and the restoration work to which it was subjected, but also reveal, while fully respecting them, the interesting technical solutions adopted by the artist in the genesis of the work, which represent the often scarcely visible, but most essentially material, aspect of ancient paintings.