Maria Carolina Peña Mariño
Easel Painting Conservator
The Dogana with Santa Maria della Salute by Francesco Guardi
The technical study of The Dogana with Santa Maria della Salute was done between November 2018 and June 2019, in parallel to the painting's conservation treatment at the Hamilton Kerr Institute (HKI), University of Cambridge, where I was an Advanced Intern in the Conservation of Easel Paintings. The objective of the study was to understand the materials and techniques used by Francesco Guardi for the build-up of this painting, and was part of the HKI and the Wallace Collection's Venice Vedutta Project.
This study implied a thorough observation of the surface under magnification in conjunction with different investigative imaging and analytical methods of examination. Initially, UV light photograph (UV), X-Radiography (XR) and Infrared Reflectography (IRR) were performed, in addition to microphotography, which provided valuable information about historical conservation treatments, changes to composition, sequence of construction of the image, characteristics of the materials used and methods of application. Additionally, four micro samples were taken from areas adjacent to damages and losses to be mounted as cross-sections. These made possible to establish the painting stratigraphy and appreciate the morphological characteristics of the layers. Subsequently, the samples were stained with Amido-Black and Lugol Solution and were analyzed using Scanning Electron Microscopy/ Energy Dispersive X-Ray (SEM-EDX), which permitted the identification of the binding medium and the elemental composition of each layer. Finally, Micro X-Ray Fluorescence (XRF) analysis was also carried out to determine the elemental composition of the paint layers and to aid in the identification of the pigments used by the artist.
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Interesting findings about the use of extensive use of starch in this painting motivated a research project on the subject which resulted in the paper entitled "Unnoticed: The diverse uses of starch in paintings" published in the Hamilton Kerr Institute Bulletin No. 8, 2020.
Francesco Guardi, San Giorgio Maggiore with the Giudecca, c.1770, Oil on canvas, 35 x 54.7 cm. Wallace Collection, London, P517, Photography taken by Chris Timus, ©Hamilton Kerr Institute.
Francesco Guardi, The Dogana with Santa Maria della Salute, c.1770, Oil on canvas, 35 x 54.7 cm. Wallace Collection, London, P518, Photography taken by Chris Timus, ©Hamilton Kerr Institute.
The painting The Dogana with Santa Maria della Salute (and its pendant pair San Giorgio Maggiore e la Guidecca) corresponds to Guardi’s mature period and is dated around 1770 (Ingamells, J.,1985). The scene depicts the waterfront view of the Grand Canal, where several gondolas and sailboats are crossing. At the very centre of the composition is the customs house or Dogana di Mare with a very busy quay, and located at the right, the Church of Santa Maria della Salute. At the left, the Giudecca island is visible in the distance. This specific view was particularly popular in the eighteenth century (Ingamells, 1985) and so, there are more than 20 related compositions and several versions by the hand of Guardi
Support
The canvas is a single piece 1:1 plain weave and tightly woven linen fabric. X-Radiography revealed cusping along the edges confirming the painting size is original, which is consistent with Guardi’s use of standard size canvas (Russel, 1996). it also showed that the canvas was initially held to the loom or strainer by 20 evenly spaced tacks.
The original auxiliary support of the canvas was most likely a four-member wood strainer of thinner bars than those exhibited by its current stretcher. This can be attested by the slightly visible marks left by it on the painting surface.
X-ray composite -The Dogana with Santa Maria della Salute Taken by Chris Timus, ©Hamilton Kerr Institute.
Preparation layers:
The preparatory system consists of a double ground. The first ground is a translucent yellow layer of medium thickness applied over the entire surface. It is comprised mostly of gypsum bound in a mixture of starch-paste and a proteinaceous substance (animal glue, egg or casein).
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On top of the gypsum/flour-paste ground sits an opaque red-ochre ground layer of medium thickness and irregular texture. It is mainly composed of earth pigments. The predominant red colour indicates there might be a higher amount of hematite (Fe2O3) but other ochre iron oxides and hydroxides, and minerals like quartz, feldspar, gypsum and chalk are also present. In addition, red clays were found to be one of the main components of the ground as evidenced by the orange-red coarse aluminosilicates mineral clumps visible in most cross-sections.
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The red-ochre ground is made of two consecutive applications of the same mixture, which can be observed by a clear dividing line in all cross-sections. Staining with Lugol’s solution detected a starch-paste isolation layer between applications and as a final coating.
Cross-section taken from the water in The Dogana with Santa Maria della Salute photographed at 200× magnification under normal and UV light. The layer structure is as follows: a: lower ground containing gypsum; b: upper red ground first application composed of red earth pigments with aluminosilicate inclusions; c: upper red ground second application composed of red earth pigments; d: light blue paint layer comprised of lead white, Prussian blue and scattered red earth pigment particles; e: medium rich light blue paint layer comprised of lead white and Prussian blue and occasional presence of red earth pigments. Of special interest are the round-shaped translucent particles in the paint layers, some of which exhibits a blue colour ring visible in UV light
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Cross-section taken from the water in The Dogana with Santa Maria della Salute after regrinding. Photographed at 200× magnification before microchemical tests in Darkfield, after Amido Black staining in Darkfield and after Iodine testing in Darkfield.
IRR image -The Dogana with Santa Maria della Salute. Taken by Chris Timus, ©Hamilton Kerr Institute.
Veduta delle Salute e Dogana e la Guideca. Francesco Guardi. Pen and brown ink over indications in black chalk on grey-blue paper. 26.2 x 43.2 cm. ©Ashmolean Museum. Oxford, UK.
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No trace of under-drawing could be identified using infrared reflectography. This could be explained by the fact that this painting lacks a reflective white ground layer. Also the artist might have used a non-absorptive IR radiation material for the under-drawing like iron-gall ink, metal point, chalk, etc., instead of the more easily detectable carbon black.
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The pen and ink drawing Veduta delle Salute e Dogana e la Guideca in the collection of the Ashmolean Museum, Oxford, thought to be done on-site by Guardi (Ingamells, 1985), could be considered an early study for this particular painting. Despite minor differences in the spatial recession and some missing elements, the location and position of the gondolas on the foreground, plus the number and postures of the gondoliers is roughly the same.
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The main difference found between the painting and the drawing are the sailboats located at the left, which are missing in the sketch. This precise arrangement, however, is found in other paintings by the artist. This illustrates how Guardi borrows elements from early studies and previous works in the layout of his paintings, an aspect that he will continue to develop through his career reaching an apex with his Capriccios. This way of approaching composition, plus the fact that there are several versions of the same veduta showing slight variations in the foreground, point to the artist’s systematic way of working tied to the demand of his Grand Tour clients.
1. Detail of HKI3283 The Dogana and Santa Maria della Salute. Wallace Collection. 2. Detail of NG2098 Venice: The Punta della Dogana. F. Guardi. ©National Gallery London. 3. Detail of NG6157 Venice: The Guidecca with the Zittele. F. Guardi. ©National Gallery London. 4. Detail of NG6156 Venice: The Punta della Dogana. F. Guardi. ©National Gallery London.
Paint layers:
The painting technique is oil paint. According to the elemental analysis, the palette used by the artist for this specific painting consists most likely of Lead White, Chalk, Naples Yellow, Yellow Ochre, Red Earths, Vermillion, Sienna, Umber, Van Dyke Brown and either Carbon or Bone Black, plus Prussian blue and Red Lake pigments. This is consistent with the findings in its pendant pair and with the standard palette reported in other technical studies of paintings by the artist (Spande, H., 2006) (Albertson, T.,1981).
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The presence of Prussian blue pigment was characterized by a ubiquitous but mild iron signal detected in SEM-EDX within the blue paint layers, consistent with the presence of small amounts of very tiny but high tinting power pigment particles observed in the cross-sections performed. Coarse blue agglomerates also present in these layers exhibit strong signals in the Kα for aluminium, which might indicate alum was used as a substrate for Prussian blue. Calcium, silicon and starch were also noted in association with the blue pigment, which could suggest either a mixed substrate (Richard, 2002), the use of extenders (Kirby & Saunders, 2004) or the adulteration of the pigment (Eastaugh, N., et al., 2004).
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Faded red lake pigments carried by starch granules were identified both in this painting and in San Giorgio Maggiore with the Guidecca (HKI3282/P517), which were used by Guardi to achieve his characteristic pinkish atmospheric skies.
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Organic pigments with a starch substrate have been found in other paintings by the artist (Peña Mariño, M. C., 2020) and by his contemporaries (Kirby & Saunders, 2004).
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Micro spot XRF spectra taken from the red top of one of the men in the water. Mayor elements detected: Lead (Pb) and Iron (Fe). Minor elements detected: Mercury (Hg), Calcium (Ca), Manganese (Mn)- Possible pigments present: Lead White, Earth pigments, Vermillion, Red Lead.
Cross-section taken from the water in The Dogana with Santa Maria della Salute (Figure 3) subject to SEM-EDX analysis. Notice the round-shaped particles in the paint layer visible in Backscatter Electron Image and how these particles don’t exhibit signal in the elemental maps for Al-K, Ca-K, Si-K, Pb-K.
Macrophotograph showing Guardi’s shorthand technique for painting figures – The brown-black outlines show a tinny craquelure pattern associated with the drying process. The gritty quality of the surface is also visble.
Overall, the painting's surface exhibits the gritty quality distinctive of Guardi, accomplished by the deliberate addition of irregular pigment particles of different sizes when mixing the paint. This is visible at plain sight, under magnification and throughout all cross-sections, where very fine particles to large coarse clumps of different colours are detectable.
The artist uses the paint at different consistencies, adjusting the amount of oil medium according to the specific needs of the passage depicted. This enables him to achieve opaque colour blocks, medium thickness impastos, thin glazes and fluid brushstrokes.
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This painting is characterized by an atmospheric quality achieved through the scumbling and free handling of the paint and the use of dabs and flecks of colour. On top, quick calligraphic brushstrokes of fluid paint capture the figures in action and the dazzling effect of light on the water.
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