Explorant l'Or

  • Exploring gold

    Throughout the more than eighty years of the Museum's conservation laboratories, many different criteria have been applied for interventions in gilded works, many of them are now obsolete but which very much remain part of our history and are still visible in the collection. Our team of specialists currently apply advanced methodologies which include, documentary study, examination, scientific analysis, and conservation methods that respect each work of art. They allow us to understand, identify and preserve the materials used in the metal decorations that have suffered wear or corrosion and which have often been altered or have even disappeared.

     

    As reflected in some medieval paintings’ contracts, clients requested gilding techniques specifically and artists obeyed by applying it in agreed locations. The optical properties of gold in reflecting light served to draw attention to areas that were symbolic, such as holy figures’ halos or auras. But its purpose was also to demonstrate wealth and prestige with brilliant and rich golden details and surfaces, such as cloudscapes or backgrounds and carved-wood frames, imitating the goldsmithery. Some of the most common ornamental resources of this technique were gilded relief decorations, punch marks, applying paint on leafs of burnished gold, sgraffito and applying transparent lacquer. These techniques could give more authenticity to the representation of certain objects, such as pieces of precious metal or embroidery, brocaded velvet fabric and other luxurious fabrics.

     

    However, all that glitters is not necessarily gold... Throughout history, metal leafs, especially of tin and silver, which are less expensive than gold have also been used with the intention of representing, for example, a suit of armour or other silver objects. Other times, tin and silver sheets were covered with a yellowish varnish called mecca gilding to imitate gold and save on costs: a well-known example is the metal decorations on wood in Romanesque paintings. And we have recently found that, as indicated in the old treaties, metal leafs were also used in Romanesque mural paintings. We have identified remains of tin metal sheets, probably covered with that varnish, in the cruciform nimbus of Christ of Sant Climent de Taüll, one of the Museum’s masterpieces.

     

    You can discover all this in Exploring gold. Investigating the gold in the paintings of the museum and during the guided visits.

     

    Mireia Mestre

    Head of the Department of Restoration and Preventive Conservation

  • 1. We study

    We use scientific analysis and the study of historical sources and documents to learn about the techniques, the materials and the tools that are used to create works of art.

     

    Lluís Borrassà and Guerau Gener, Nativity and Saint John the Evangelist, 1407-1411. Tempera and gold leaf on wood.

     

    Lluís Borrassà and Guerau Gener, The Resurrection of Christ, 1407-1411. Tempera, gold leaf and metal sheet on wood

  • 1.1. We study

    Ornamental resources:

     

    1. Carved wood: Some parts of wood that have an architectural, decorative and framing function are carved with cutting tools to plane them down and shape them, and they are usually gilded.

     

    2. Inlay: Ornamental relief on the ground layer, of plaster and animal glue, to which is applied a metal sheet of gold, silver, tin or copper. It imitates embroidery or precious metalwork.

     

    3. Punch marks: A gentle relief printed on a gilt or silver plated surface, obtained by the pressure of iron tools ending in circles, stars, squares, lines, peaks...

     

    4. Rotella: The repeated engraving of a simple figure, such as a small circle or a dot, made with a small wheel, attached to the end of a handle.

     

    The materials and techniques:

     

    5. Zwischgold: Gold leaf on silver leaf, beaten together, that is used to gild marginal areas and thus lower costs.

     

    6. Gold leaf: A very thin lamina that is obtained by craftsmen, called batifullers (goldbeaters), by beating the metal with a hammer. It is used to gild surfaces previously prepared (armenian bole), with a goldcushion, a gold knife and a gilder’s tip.

     

    7. Shell gold: Sheets of gold ground up and mixed with an agglutinant. Like paint, it is applied with a brush. It is used in the decorative motifs of fabrics.

  • 1.2. We study

    Ornamental resources:

     

    1. Estofat (Quilting): A technique that imitates a fabric or quilt by applying burnished gilt, which can then be painted and, when it is dry, sgraffitoed or stippled.

     

    The materials and techniques:

     

    2. Burnishing: Polishing the surface of the metal sheet, done with an agate burnisher, to obtain a gleaming finish.

     

    3. Armenian bole: A very fine ochre, red and grey clay, used to  prepare supports that have to be gilded or silver plated in water. It is mixed with diluted rabbit skin glue and applied, in thin layers, on the smooth surface, prepared with plaster or chalk -whiting (Spanish white)- and animal glue.

     

    4. Mecca varnished silver: The application of a yellowy glaze on silver leaf. The gleam is similar to that of gilt.

  • 2. We analyse

    In some cases, we make checks with the analysis of micro-samples, which are taken from the work in order to identify the materials. The analysis of a sample from the mural painting from Sant Climent de Taüll has revealed traces of mecca varnished metal sheet sheeting imitating gold.

     

    A lamina of tin (Sn), shiny like metal, is identified on top of the white mortar.

     

    Master of Taüll, Apse of Sant Climent de Taüll, circa 1123. Fresco transferred to cloth.

  • 2.1. We analyse

    Instrumental analysis techniques :

     

    1. Ultraviolet light: It enables us to distinguish additions, repaints and varnishes, due to the different fluorescence and reflection of the materials, illuminating the work with ultraviolet radiation.

     

    2. Infrared reflectography: It enables us to study the underlying drawing of the paint layers based on the optical properties of the materials, exposed to infrared radiation. A sensitive camera processes the radiation reflected by the  object and a mosaic of images or reflectograms is obtained.

     

    3. Optical microscopy: Preparations of samples are observed at different magnifications and with different illumination techniques to determine morphologies, distributions of particles and layers, sizes or colours.

     

    4. Electronic microscopy: It enables us to obtain high-resolution black and white images at large magnifications, which tell us about the morphology and the chemical composition of the sample. It makes it possible to obtain spectra of chemical elements.

     

    5. Infrared spectroscopy: It enables us to identify chemical compounds through characteristic spectra, resulting from the interaction of IR energy radiation with the material’s molecular links.

  • 3. We act

    The materials used in art age, change and deteriorate. We make a diagnosis and try to act on the causes of degradation. We also work on the areas of colour loss to restore the work’s colouring. The restorations of painting must always be reversible and they must make it easy to interpret the work of art.

  • 3.1. We act

    1. Stippling with a paintbrush or an airbrush: In a large area of paint loss, a brush full of paint or an airbrush is used to obtain a cloud of small coloured dots that gives an evenly spread result.

     

    2. Chromatic abstraction or cross-hatching: Very thin criss-crossed lines of pure colours are applied, close together, without constructing shapes or volumes, based on the predominant colours in the work.

     

     

    Master of Vallbona de les Monges (Guillem Seguer [?]), Frontal of the Corpus Christi, circa 1335-1345. Tempera, stucco reliefs and yellow-glazed metal sheet on wood.

     

    Master of Estopanyà, Altarpiece of Saint Vincent, circa 1350-1370. Tempera and gold leaf on wood.

  • 3.2. We act

    3. Tratteggio (o rigatino): As its name in Italian, “hatching”, indicates, very thin vertical parallel lines of pure colours are applied, close together, that from a certain distance cannot be distinguished.

     

    4. Neutral ink: A neutral uniform colour is applied on the lost parts. The shade is a compendium of all the colours in the work and it is perceived as being duller.

     

     

    Ramon de Mur,  Virgin suckling the child, circa 1415-1425. Tempera and gold leaf on wood.

     

    Joan Gascó, Altarpiece of Saint Peter, circa 1516. Tempera, oil paint, stucco reliefs and gold leaf on wood.

  • 3.3. We act

    5. Pointillism: Multiple very small dots of pure colours are applied, which are superimposed and create a sort of chromatic vibrancy. From a certain distance, they cannot be perceived separately.

     

    6. Illusionism or mimesis: The lost areas are restored to look the same as the original, provided they are not figurative elements. In the past, the colour, the shape and the texture were imitated, so that the restoration could not be distinguished from the original.

     

     

    Joan Mates, Calvary; Saint Sebastian, 1417-1425. Tempera, gold leaf and metal sheet on wood.

     

    Joan Reixach, Saint Margaret, circa 1456. Tempera, oil paint and gold leaf on wood.