‘Capriccio: Antique Ruins and a Distant Town’; one of eight large scale capricci paintings from the Dining Room at Shugborough Hall, National Trust. Distemper (pigment bound with animal glue) on canvas. With a complex attribution history: seven of the Capricci are by Pietro Paltronieri (1673–1741); two were later extended by Biagio Rebecca (1731–1808); and the eighth has recently been re-attributed to Antonio Joli (1700-1777). Conservation of the eight large scale paintings took place between October 2018 and December 2019 and was funded by the National Trust.
The capricci paintings were prioritised for conservation work owing to the instability of the distemper paint layers, which were lifting and flaking away from the canvas support. In October 2018 a mapping survey was undertaken, whereby each painting was carefully assessed in a raking light, and areas of flaking were documented. A rating system of ‘severe’, ‘moderate’ and ‘mild’ flaking were followed, and the affected areas indicated with either red, amber or yellow outlines. This mapping exercise would help with the longer term monitoring of these vulnerable and sensitive distemper paintings.
©National Trust/photographer unknown
This photograph has been taken in raking light, whereby the light source glances across to emphasis the surface topography of the painting. The extent of the flaking distemper paint layers is revealed by this type of photograph. Each of the areas indicated with a letter, e.g. ‘A’, ‘B’, ‘C’ etc in the mapping image, was photographed in raking light before, during and after treatment.
©National Trust/Lucy Critchlow
Samples were taken from several of the capricci before treatment was carried out. This involved using low magnification to take a minute paint layer cross-sections using a scalpel blade and fine sable brush. The samples were sent off to specialists in paint sample analysis. The results would help direct the conservation treatments to be carried out, as well as supplementing the growing body of research into these unusual paintings.
©National Trust/Pia Dowse
In this detail of ‘Capriccio: Antique Ruins and a Distant Town’, you can see how Pietro Paltronieri applied the distemper paint layers thickly to create body and opacity to describe the architecture and figures. Cross-section analysis of the paint layers also showed that a cream coloured ground layer had been applied to the original canvases prior to painting.
The canvas preparation, paint layer application and style of the original canvases differs greatly from the later additions by Biagio Rebecca, which you will see in the next image.
In this detail photograph you can see the sketchy painting style employed by Biagio Rebecca (1731–1808) who extended two of the capricci paintings: ‘Capriccio: Antique Ruins with a Pyramid’; and ‘Capriccio: Roman Ruins at Bologna’. A fairly dry distemper paint has been used to create sketchy outlines of the archtiectural ruins in this scene, and the unprimed canvas is left bare in many areas, its colour contributing to the tonality of these later additions.
©National Trust/Lucy Critchlow
In this detail photograph you can see one of the hand stitched canvas seam running down the length of ‘Capriccio: Antique Ruins with a Pyramid’. To construct such large scale paintings, it was necessary to stitch several canvases together. This painting is one of the largest capricci, measuring approximatley 274cm in height by 300cm in width.
©National Trust/Lucy Critchlow
The eight capricci were conserved systematically, over a one year period. The conservation work took place in the Dining Room and in front of the public, as part of the National Trust ‘Conservation in Action’ scheme. Owing to space constraints, one capricco was taken down and conserved and replaced into position before the next capricco was taken down for treatment.
The first stage of treatment was to stabilise the flaking paint layers. A selection of adhesives were tested for their suitability in consolidating the distemper paint layers and re-adhering them back down onto their canvas supports. Test results showed that the best adhesive for these particular paintings was a mixture of Isinglass (a fish glue derived from the swim bladder of the Sturgeon fish) and Jun Funori (a Japanese glue extracted from the red algae genus Gloiopeltis). The mixture of these two adhesives gave the matt properties required to tie in with the matt paint layers, as well as providing the adhesive strength required to re-adhere the flaking layers back down onto the canvas support.
Consolidation of the paint layers was a painstaking and intricate task. The warmed adhesive mixture was applied to the paint layers using a fine sable brush, and allowed to flow between the paint layers and canvas. Excess adhesive was cleared and the paint layers were laid back down onto the canvas using gentle heat and pressure supplied by a thermostatically controlled spatula.
©National Trust/Lucy Partridge
Where possible, the paint layers were consolidated whilst the paintings were supported horizontally, on work tables. This allowed the adhesive to flow down between the paint layer and canvas and reduced the risk of any flakes of paint falling away and becoming lost. It was possible to reach approximately 90cm in towards the centre of each painting.
©National Trust/Lucy Critchlow
This photograph shows lifting and flaking paint layers in the upper left area of sky in ‘Capriccio: Antique Ruins and a Distant Town’, before treatment.
©National Trust/Lucy Critchlow
This photograph shows the same area after the lifting and flaking paint layers had been sucessfully consolidated.
©National Trust/Lucy Critchlow
Once the paint layers had been consolidated and stabilised, it was possible to begin surface cleaning.
Tests were carried out to determine the safest method and cleaning mixture to remove 28 years worth of dust and dirt, which had accumulated on the surfaces of each capricci.
Cleaning was then carried out using cotton wool swabs and the chosen cleaning solvent. Here you can see the top edge of the painting has been cleaned, and the conservator works systematically down the left edge of the painting. As noted previously, it was possible to reach approximatley 90cm in towards the centre of each painting using this method.
©National Trust/Lucy Critchlow
This during treatment photograph shows the dramatic tonal lift as 28 years of dust and dirt were cleaned from the surface of the painting.
©National Trust/Lucy Critchlow
Once the 90cm width perimeter of the larger paintings had been sucessfully consolidated and surface cleaned, the paintings were supported upright on a large A-frame. The central area of each painting could then be reached and treated either standing, using steps or using a small scaffolding tower.
©National Trust/Lucy Critchlow
The final stages of treatment involved in-painting any damages or losses, and applying fine glazes to reduce the appearance of old discoloured over-paint layers. Retouching was carried out using dry pigments bound with a stable synthetic binder.
©National Trust/Lucy Critchlow
Fabric backings were removed from the reverse of each painting, to reveal the underlying stretcher and canvas.
You can see that the stretcher for this capriccio was in generally good condition. The majority of the capricci had undergone major structural work in the 1990s. The structural work often included lining treatments, which involved adhering the original weakened canvases onto new heavy weight Belgium linen canvases using a heat seal adhesive, and restretching the paintings back onto their refurbished stretchers. The linings dating to the 1990s were found to be in excellent condition and the treatment required on the reverse of each painting was minimal.
©National Trust/Lucy Critchlow
Dust and debris at the reverse of each canvas and stretcher was cleaned using a Museum Vac and Dry Cleaning Sponge.
©National Trust/Lucy Critchlow
Some of the stretcher keys were not secured to their stretchers. During handling and re-installation there was a risk that the keys would fall out of their key slots and become lodged between the lower stretcher bar and canvas. This could cause bulge disortions and paint layer damage at the front of the painting.
©National Trust/Lucy Critchlow
Monofilament line and brass screws and cups were used to secure the keys to the stretcher.
©National Trust/Lucy Critchlow
Finally, a breathable but waterproof fabric backing was attached to the reverse of each capricci, to protect them for the future.
©National Trust/Lucy Critchlow