Tag: tempera

In-situ in Southern England

From the 6th to the 8th of April 2016, Senior Painting Conservator Christine Slottved Kimbriel and I (Carlos González Juste, 2nd year postgraduate Intern) worked in-situ treating an altarpiece in a parish church in the south of England. The altarpiece is an Italian tryptich dated to the second half of the 14th century, and currently attributed to Pietro Nelli, a Sienese artist working in the tradition of Giotto.

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Details showing the egg tempera technique and the scoring and punching embellishing the gilt halo and the crozier. (© González Juste)

Like with many art objects not kept in a museum environment, this altarpiece has to face typical church conditions, including changes in temperature and relative humidity, the occasional birds droppings, and also the effects of the presence of bats which frequent the building.

Frequent and uncontrolled changes in relative humidity have an adverse effect on panel paintings, as wooden supports tends to respond with expansion and contraction. These movements affect not only the panel (- which may split if it does not have space to move in the frame) but also the paint layers and gilding, producing cracks, flaking and subsequently paint loss.

Bats are common in churches and their roots are protected by legislation. The damage produced by the corrosion of their urine and guano can be considerable, especially on the painted surface where it damages both the varnish and the paint.

The in-situ work on the altarpiece started with a full visual examination of the three panels, their structure and frame. In spite of its overall sound state of preservation, the altarpiece required consolidation of loose and vulnerable areas of paint and gilding, both on the panels and on the 19th century gilt frame. After consolidation with Lascaux© Medium for Consolidation, surface dirt and several bird droppings were removed, some areas of deteriorated varnish saturated with new varnish application and losses filled and toned. The project required us to work from a scaffolding in order to reach all areas of the panels. The surface cleaning removed a considerable build-up of surface dirt and produced a significant improvement to the general appearance of the painting, allowing the astonishingly well-preserved bright colours of the robes and the delicate flesh tones of the faces to come across once again.

Some minor technical investigation was undertaken, and in spite of the challenging conditions of working in-situ and under a time constraint, close optical examination and local infrared photography was accomplished, providing some interesting results.

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White garment of St Julian during surface cleaning. (© González Juste)

It is quite common that members of the Institute have to travel to work in-situ in churches, country houses or local museums. The reasons for choosing to work on site, rather than bringing the work to the studio, vary. It may be the right option when the painting is particularly heavy or large, or when its absence is considered unacceptable, as may be the case for an altarpiece that plays a vital part in daily worship. A painting can also be in a particularly delicate state of preservation that necessitates work being undertaken prior to moving the object, or conversely, one or more paintings are in need of only minor, preventive or aesthetic intervention that can be done more cost-effectively on site.

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González Juste undertaking surface cleaning. (© Kimbriel)

In-situ jobs are always very interesting and useful opportunities for interns, as they give us the opportunity to visit and discover different parts of the country, and especially their works of art. It also helps interns to develop their abilities when they have to face treatments in challenging circumstances and under time pressure, far away from the well-equipped studio. In-situ jobs not only provide the gratification of a job well done, but it also sometimes includes the privilege of seeing how conservation work can have positive repercussions on the daily life of the surrounding community, as was the case here. Having the opportunity to work on a magnificent altarpiece in a beautiful location was truly a pleasure, not least thanks to the helpfulness and interest of the church community, who were eager to see this beautiful work of art to which they feel attached preserved and safe for the foreseeable future.

Carlos González Juste – 2nd year Post Graduate Intern at the Hamilton Kerr Institute.

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Senior Painting Conservator Christine Slottved Kimbriel explaining the treatment and characteristics of the altarpiece to members of the community. (© González Juste)

About the author

Carlos González Juste has a B.A. in History from the Complutense University in Madrid and a Degree in Conservation and Restoration of Cultural Heritage from the Escuela Superior de Conservación y Restauración de Bienes Culturales in Madrid.  He has interned in the Museo Nacional del Prado (Madrid) and other Spanish institutions. He is currently completing his second year as a postgraduate Intern at the Hamilton Kerr Institute, University of Cambridge, where he has been working on a wide range of projects, from early Italian paintings, such as the Master of the Castello Nativity, to early C20th Russian artist A. Harlamoff, besides paintings by J. Reynolds, W. van Mieris and the C17th English painter R. Buckett.

To contact Carlos González Juste: cgjuste@gmail.com

The Restoration of a Virgin and Child Tondo for the Madonnas & Miracles Exhibition at the Fitzwilliam Museum

This School of Botticelli tondo depicting the Virgin and Child was bequeathed to the Fitzwilliam Museum in 1912. During the autumn of 2015 it came to the Hamilton Kerr Institute in preparation for a loan. Upon initial inspection it became clear that the heavily blistering and slightly flaking panel was likely to be under internal stress from the battens on the reverse. Due to the importance of the piece and its projected display at the Botticelli Reimagined exhibition at the V&A (2016) and the upcoming Madonnas and Miracles exhibition at the Fitzwilliam Museum (7 March – 4 June 2017), it was possible to raise funds to allow us to fully explore the cause of the blistering and undertake a complete conservation and restoration treatment. During the treatment it was found that certain paint layers and the paint medium deserved further investigation.

Structural Work

The paint and ground layers were consolidated before structural work could commence. Over time, a number of cracks had begun to form in the wooden support from the edges inwards, resulting in local tenting of the ground and paint layers. These fragile layers were secured and visibly improved during the consolidation treatment, which offered a better overall surface of the painting. The presumed tension, manifested in the cracks from the edges of the panel, was supported by the fact that the battens, which appear to be non-original, were unable to move in the original dovetail grooves. It was therefore decided to temporarily remove the battens and plane down the areas causing friction in order to fit them back into their grooves. In their slightly thinned state they will in the future provide support without restraining slight natural movement of the poplar panel in response to minor shifts in relative humidity.

Pigment and Medium Analysis

X-ray Fluorescence spectroscopy (XRF) and cross section analysis respectively were employed to determine the pigments used and to observe layer structures in order to enable comparison with other paintings.1,2 An elemental composition reading of specific passages was attained with the non-destructive XRF technique. This in turn allowed well-informed sampling for cross sections to illustrate the build-up of layers. The pigments and layer structure were found to correspond to a typical build-up in late 15th century Florentine paintings3 comprising of a white gesso layer on top of the wooden support followed by a glue priming, and in some cases a white oil priming, which was then finished off with the actual paint layers.

However, unlike many of Botticelli’s paintings, this tondo did not show the characteristic hatching typical of egg tempera painting technique. The presence of brushstrokes and impasto suggested the use of either an oil rich tempera grassa4 (an egg and oil emulsion medium) or neat oil paint. A small sample was removed from an area of loss in the light sky area in order to investigate the medium that was used. With the aid of cross section staining (using ), it was possible to conclude that very little to no protein (egg) was utilised in the paint layers, whereas the glue and ground layers stained positive for protein. A reason for this slightly unusual choice of medium for Botticelli’s workshop and period may have been influenced by guidelines of the commission, the patron, or a desired visual impact.5

Varnish and Grey Layer Removal

After successful surface cleaning and varnish removal a selectively applied grey layer extending over the flesh, Virgin’s robe, and some of the background, became apparent. This resulted in a ‘veil’ concealing the delicate shading of the faces and drapery. During inspection under the microscope, it became clear that this layer extended into cracks and was therefore unlikely to be original. Solvent tests determined a suitable cleaning solution and enabled the safe removal of the grey, obscuring layer.  The painting thus regained its original tonal values and balance of highlights and shadows.

Restoration: filling and retouching

Paraloid® B72, a stable synthetic resin, was applied as a transition layer to saturate paint layers after successful consolidation and cleaning of the painting. Subsequently, the losses were filled with a water soluble putty consisting of chalk and gelatine. These losses were then textured to emulate the surrounding area and retouched using the retouching technique traditionally employed at the Hamilton Kerr Institute: First, lightfast loose pigments bound in egg tempera medium are applied to achieve the opaque lower/baselayers of the painting, which are then followed by pigments bound in a synthetic resin, in this case Gamblin Conservation Colours™, to imitate final glazes. A final synthetic resin varnish was spray-applied to even out the gloss of the painting. The composition-gilt frame that had received glazing for the exhibition was lined with gummed paper tape and self-adhesive felt tape to reduce the risk of abrasion from the rebate to the painting’s edges. Brass plates affixed to the frame were shaped to fit the painting and hold it securely in its frame. In order to protect the painting better from fluctuations in humidity and dirt a hardboard backing was screwed onto the reverse of the frame.

Michaela Straub – 3rd year student at the Hamilton Kerr Institute

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About the author

Currently in her third year studying easel painting conservation at the Hamilton Kerr Institute, Michaela Straub graduated from Aberystwyth University with a BA in Fine Art and Art History in 2012. She has undertaken internships in private studio’s, the Denkmalschutzamt in Germany and the Kunsthistorische Museum in Vienna.

To contact Michaela Straub: straubmich@aol.com

  1. Bersani, P. P. Lottici, A. Casoli, and D. Cauzzi, ‘Pigments and binders in “Madonna col Bambino e Giovannino” by Botticelli investigated by micro-Raman and GC/MS’, Journal of Cultural Heritage, vol. 9, 2008, pp. 97-102.
  2. Castelli, M. Ciatti, C. Lalli and A. Ramat, ‘Il Restauro del Ritratto di Giovanne con Mazzocchio di Sandro Botticelli’, OPD Restauro: Rivista dell’Opificio delle pietre dure e laboratorio di restauro di Firenze, vol. 23, 2011, pp. 141-154.
  3. Dunkerton and A. Roy, ‘The Materials of a Group of Late Fifteenth-century Florentine Panel Paintings’, National Gallery Technical Bulletin, vol. 17, 1996, pp. 20-31.
  4. Dunkerton, ‘Modifications to traditional egg tempera techniques in fifteenth-century Italy’, Early Italian Paintings Techniques and Analysis Symposium, Maastricht 1996.
  5. Dunkerton, ‘Osservazioni sulla tecnica delle opera di Sandro Botticelli alla National Gallery di Londra’, in: D. Gasparotto, A. Gigli, F. Motta, Il tondo di Botticelli a Piacenza, Milan 2006, pp. 67 – 79.

More painting reconstructions: gilding and punching

In the previous post, I shared my experiences of making a reconstruction from a detail of Virgin Adoring the Child by Jacopo del Sellaio (dated c. 1473). While creating the copy, I learned about the materials and methods utilized for painting with egg tempera. The use of egg tempera is characteristic of early Italian paintings. Similarly, decorative gilding goes hand-in-hand with early Italian artworks. Halos of saints, fabrics, and even entire backgrounds can all be depicted in gold. A range of gilding techniques could be employed, depending on the visual effect the artist wanted to achieve.

Virgin and Child by Niccola di Pietro Gerini – Fitzwilliam Museum
Virgin and Child by Niccola di Pietro Gerini – Fitzwilliam Museum

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