Conservation and restoration of frescos

Last updated
Restoration of wall paintings, Ephesus Restoration Wall Paintings, Ephesus.jpg
Restoration of wall paintings, Ephesus

The conservation and restoration of frescoes is the process of caring for and maintaining frescos, and includes documentation, examination, research, and treatment to insure their long-term viability, when desired.

Contents

Technology

Fresco is a technique of mural painting in which pigment is applied to freshly-laid or wet lime plaster. Water acts as a type of binding agent that allows the pigment to merge with the plaster, and once the plaster sets the painting becomes an integral part of the wall.

Materials (chemical make-up)

Lime cycle LIME CYCLE.jpg
Lime cycle

Fresco chemicals consist of the following:

Calcium carbonate (limestone) is decomposed by heat to produce calcium oxide (quicklime) and carbon dioxide gas. Then calcium oxide reacts with water to form calcium hydroxide (slaked lime) which is accompanied by the release of heat, a reaction known as exothermic. [1]

Pigments used from antiquity to the early 19th century

[2]

Deterioration of frescoes

Hades abducting Persephone Hades abducting Persephone.jpg
Hades abducting Persephone

Frescoes can be found in places of worship such as churches, ancient temples and tombs, as well as private residences and commercial establishments used for public entertainment. It is these environments and their pollutants that interact with the chemicals, both organic and inorganic, utilized to create the frescoes and the pigments used that contribute to their aesthetic and structural deterioration. Additionally, wall paintings such as frescoes depending on the technique used, possess a layered structure consisting of support, ground or paint layer. These constituents of wall paintings undergo deterioration physically, chemically or biologically. Although factors like moisture, salts, and atmospheric pollution have generally been the main contributors to the deterioration of wall paintings in most cases, many in the field believe the growth of biological agencies like fungi and microbial flora is also responsible for decay. [3]

Chemical degradation

The presence of pigment discoloration, stains and the formation of bio-film are indicative of chemical degradation. Given the variety of organic and inorganic molecules present in frescoes, many type of micro-organisms may grow on the substrate of the fresco provided that environmental conditions (humidity, temperature, light, and pH) are fostered. [4] Chemical deterioration can be attributed to fungi through their metabolites either by assimilation or dissimulation processes. In the assimilation process, the fungi use the components of frescoes as a carbon source through enzyme production, whereas in the dissimulation process, the decay is mainly by the excretion of waste products or secretion of metabolic intermediates including acids and pigments which can damage, stain or disfigure the surface. [3]

Physical degradation

Fresco in the terrace houses in Ephesus Fresco in the Terrace Houses in Ephesus (6).JPG
Fresco in the terrace houses in Ephesus

Signs of cracking and disintegration of paint layers and the formation of paint blisters is indicative of physical/structural degradation. Industrial pollutants contain gases and burning fossil fuels which react with oxygen and water to produce sulfuric acid and nitric acids. These acids convert calcium carbonate (limestone) to calcium sulfate which becomes soluble in the water and it forms large crystals within the surface layer causing the fresco to blister and flake off. [1] Aside from the adverse effects of environmental pollutants, fungal growth either on or below the surface can cause the dislodging of the paint layers further contributing to the physical and structural degradation of frescoes. [5]

Preventive care

Frescoes that have been removed from their original context and relocated to cultural institutions have the benefit of being in a more stable environment that is consistently monitored, even though they are at low risk. However, for frescoes still at their place of origin, such as cultural heritage sites, are at high risk because they are vulnerable to environmental elements due to a high volume of tourist traffic in conjunction with other pollutants. Therefore, as with any similar object, data loggers are useful to monitor ambient conditions such as temperature and relative humidity, as well as thermohygrometric sensors for micro-climate monitoring for fresco paintings in indoor, outdoor or semi-confined environments. [6]

Cleaning methods

Cleaning aims to restore artworks to how the artist intended them to look; however, how an artwork is cleaned will depend on the nature of the material to be removed. With paintings, a variety of organic solvents are used, but the most common solvent is water, often with chelating agents, surfactants or salts to control pH. Applying solutions through tissues, gels and sponges is becoming the norm, due to the level of control offered by holding the cleaning system at the upper surface of the art. Such gels, introduced in the late 1980s, are usually water-based emulsions thickened with cellulose or synthetic polymers. By slowly releasing the solvent, they prevent some of the swelling damage that free solvents cause to paint layers. During the 1960s, it became popular to use synthetic polymers to consolidate and stabilise frescoes – plaster-based wall paintings. They seemed like the perfect replacement for the wax coatings previously used, but over time it became clear that this was not the case. Their presence drastically changed the paintings' surface properties, causing mechanical stresses and crystallisation of salts beneath the painting leading to accelerated disintegration. In addition, the polymers themselves became discoloured and brittle. [7] By the mid-1990s, laser cleaning was established for stone and started to be used for other materials such as gilded bronzes and frescoes. A major breakthrough came when an Italian physicist at the National Research Council Institute of Applied Physics in Florence, Salvatore Siano, developed a method that used even shorter pulses, of only micro- to nanosecond duration. [7] Another major innovation in the last decade is the use of colloid science and nanotechnology in conservation. In the mid-1990s colloid scientist Piero Baglioni came up with a microemulsion: a clear mixture of organic solvent and water, stabilised with a surfactant that sits at the interface between the water and organic phases. Another unusual method of cleaning frescoes is with the use of specific types of bacteria to remove inorganic crusts and animal glues from frescoes. Because bacteria can produce a whole host of enzymes they can deal with complex cleaning problems, metabolising organic and inorganic matter into hydrogen sulfide, molecular nitrogen or carbon dioxide. [7]

Repair and restoration techniques

MI - Sant'Eustorgio - Sottocoro - Restauratrice - Foto Giovanni Dall'Orto - 1-Mar-2007 IMG 6172 - MI - Sant'Eustorgio - Sottocoro - Restauratrice - Foto Giovanni Dall'Orto - 1-Mar-2007.jpg
MI - Sant'Eustorgio - Sottocoro - Restauratrice - Foto Giovanni Dall'Orto - 1-Mar-2007

During the 18th century, new techniques were perfected for the restoration and conservation of ancient works of art, including methods of detaching fresco paintings from walls. Detachment involves separating the layer of paint from its natural backing, generally stone or brick, and can be categorized according to the removal technique used.

The oldest method, known as the a massello technique, involves cutting the wall and removing a considerable part of it together with both layers of plaster and the fresco painting itself.

The stacco technique, on the other hand, involves removing only the preparatory layer of plaster, called the arriccio together with the painted surface.

Finally, the strappo technique, without doubt the least invasive, involves removing only the topmost layer of plaster, known as the intonachino, which has absorbed the pigments, without touching the underlying arriccio layer. In this method, a protective covering made from strips of cotton and animal glue is applied to the painted surface. A second, much heavier cloth, larger than the painted area, is then laid on top and a deep incision is made in the wall around the edges of the fresco. A rubber mallet is used to repeatedly strike the fresco so that it detaches from the wall. Using a removal tool, a sort of awl, the painting and the intonachino attached to the cloth and glue covering are then detached, from the bottom up.

The back of the fresco is thinned to remove excess lime and reconstructed with a permanent backing made from two thin cotton cloths, called velatini, and a heavier cloth with a layer of glue. Two layers of mortar are then applied; first a rough one and then a smoother, more compact layer.

The mortars make up the first real layer of the new backing. The velatini cloths and the heavier cloth serve only to facilitate future detachments, and are therefore known as the strato di sacrificio, or sacrificial layer. Once the mortar is dry, a layer of adhesive is applied and the fresco is attached to a rigid support made from synthetic material which can be used to reconstruct the architecture that originally housed the fresco. After the backing has completely dried, the cloth covering used to protect the front of the fresco during detachment is removed using a hot water spray and decoloured ethyl alcohol. [8]

Piero Baglioni has also pioneered the use of nanoparticles for repairing deteriorating frescoes. Artists generally painted directly onto wet calcium hydroxide plaster, which reacts with atmospheric carbon dioxide to form calcium carbonate (calcite). Over centuries, pollution and humidity causes the carbonate layer to break down and sulfate, nitrate and chloride salts within the walls recrystallize, leading to deterioration of the painted surface. Baglioni was sure that nanoparticles would improve on conventional conservation methods. His treatment injects calcium hydroxide nanoparticles dispersed in alcohol and their small size, just 10–100 nm, allows them to penetrate several centimetres into the frescoes and slowly reform the depleted calcite. [7]

Antibiotics such as amoxicillin can be used to treat strains of bacteria living in a fresco's natural pigment which can turn them into powder. [9]

Another method of fresco repair is the application of a protection and support bandage of cotton gauze and polyvinyl alcohol. Difficult sections are removed with soft brushes and localized vacuuming. The other areas that are easier to remove (because they had been damaged by less water) are removed with a paper pulp compress saturated with bicarbonate of ammonia solutions and removed with deionized water. These sections are strengthened and reattached then cleansed with base exchange resin compresses, and the wall and pictorial layer are strengthened with barium hydrate. The cracks and detachments are stopped with lime putty and injected with an epoxy resin loaded with micronized silica. [10]

Fresco restoration projects

The Sistine Chapel The Sistine Chapel (5967688938).jpg
The Sistine Chapel

Sistine Chapel

The Sistine Chapel was restored in the late 1970s and through the 1980s. This was one of the most significant, largest and longest art restoration projects in history. The entire project took twelve years to complete, not taking into account the inspections, planning and approval of the project. Among the many parts of the chapel that was restored, what drew the most attention were Michelangelo's frescoes. The restoration sparked controversy. A number of experts criticized the proposed techniques, claiming that the restoration procedure would scrape off the layers of various materials on the frescoes, which would lead to damage beyond repair, and that the removal of the materials would expose the pigments on the frescoes which were fragile and dated to artificial light, temperature variations, humidity and pollution. Such exposure, they feared, would cause massive damage to the original artwork. [11]

Villa of Mysteries in Pompeii

Fresque des myteres, Pompei Fresque des myteres, Pompei.jpg
Fresque des mytères, Pompéi

For the frescos of Villa of the Mysteries in Pompeii, early conservation efforts sometimes involved removing frescoes, rebuilding or reinforcing the walls, and then reattaching the paintings. The first conservators also applied a coat of wax mixed with oil to clean the paintings' surfaces, preserve the ancient pigments, and stabilize the fragile works, giving the frescoes a glossy appearance the ancient artists never intended them to have. At the same time, the wax filled in cracks in the surfaces, sealing moisture inside the walls, further weakening them by compromising the strength of the mortar holding the walls together. By 2013 the villa, like most of Pompeii, was in dire need of modern conservation, as was a protective covering that had been constructed in different phases throughout the years. Parts of paintings were crumbling from unstable walls and the mosaics had been severely damaged by millions of visitors' feet. Repeated applications of wax had caused the pigments to oxidize and darken, and the frescoes to yellow, significantly altering their appearance. All the surface decorations of the villa, both mosaics and frescoes, had been conserved before, but in irregular ways. Some of the methods currently being employed have been used by decades of conservators at Pompeii. Frescoes have been cleaned by hand using a scalpel or a chemical solution. Painted surfaces have been consolidated with an acrylic resin diluted with deionized water and then injected into cracks, [12] as well as the use of antibiotics for the removal of bacteria. [13]

The teams today also have more high-tech tools at their disposal, including lasers to clean the frescoes, and ultrasound, thermal imaging, and radar to evaluate the level of decay of the walls and paintings. Drones are being used to examine the entirety of the villa's protective covering.[ citation needed ]

Related Research Articles

<span class="mw-page-title-main">Fresco</span> Mural painting upon freshly laid lime plaster

Fresco is a technique of mural painting executed upon freshly laid ("wet") lime plaster. Water is used as the vehicle for the dry-powder pigment to merge with the plaster, and with the setting of the plaster, the painting becomes an integral part of the wall. The word fresco is derived from the Italian adjective fresco meaning "fresh", and may thus be contrasted with fresco-secco or secco mural painting techniques, which are applied to dried plaster, to supplement painting in fresco. The fresco technique has been employed since antiquity and is closely associated with Italian Renaissance painting.

<span class="mw-page-title-main">Oil painting</span> Process of painting with pigments that are bound with a medium of drying oil

Oil painting is the process of painting with pigments with a medium of drying oil as the binder. It has been the most common technique for artistic painting on canvas, wood panel or copper for several centuries, spreading from Europe to the rest of the world. The advantages of oil for painting images include "greater flexibility, richer and denser colour, the use of layers, and a wider range from light to dark". But the process is slower, especially when one layer of paint needs to be allowed to dry before another is applied.

<span class="mw-page-title-main">Paint</span> Pigment applied over a surface that dries as a solid film

Paint is a liquid pigment that, after applied to a solid material and allowed to dry, adds a film-like layer, in most cases to create an image, known as a painting. Paint can be made in many colors and types. Most paints are either oil-based or water-based, and each has distinct characteristics.

<span class="mw-page-title-main">Ultramarine</span> Deep blue purple color pigment which was originally made with ground lapis lazuli

Ultramarine is a deep blue color pigment which was originally made by grinding lapis lazuli into a powder. Its lengthy grinding and washing process makes the natural pigment quite valuable—roughly ten times more expensive than the stone it comes from and as expensive as gold.

<span class="mw-page-title-main">Limewater</span> Calcium hydroxide solution

Limewater is a saturated aqueous solution of calcium hydroxide. Calcium hydroxide, Ca(OH)2, is sparsely soluble at room temperature in water (1.5 g/L at 25 °C). "Pure" (i.e. less than or fully saturated) limewater is clear and colorless, with a slight earthy smell and an astringent/bitter taste. It is basic in nature with a pH of 12.4.

<span class="mw-page-title-main">Plaster</span> Broad range of building and sculpture materials

Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "render" commonly refers to external applications. The term stucco refers to plasterwork that is worked in some way to produce relief decoration, rather than flat surfaces.

<span class="mw-page-title-main">Whitewash</span> Paint made from lime and chalk

Whitewash, calcimine, kalsomine, calsomine, or lime paint is a type of paint made from slaked lime (calcium hydroxide, Ca(OH)2) or chalk (calcium carbonate, CaCO3), sometimes known as "whiting". Various other additives are sometimes used.

<span class="mw-page-title-main">Lime (material)</span> Calcium oxides and/or hydroxides

Lime is an inorganic material composed primarily of calcium oxides and hydroxides, usually calcium oxide and/or calcium hydroxide. It is also the name for calcium oxide which occurs as a product of coal-seam fires and in altered limestone xenoliths in volcanic ejecta. The International Mineralogical Association recognizes lime as a mineral with the chemical formula of CaO. The word lime originates with its earliest use as building mortar and has the sense of sticking or adhering.

<span class="mw-page-title-main">Fresco-secco</span>

Fresco-secco is a wall painting technique where pigments mixed with an organic binder and/or lime are applied onto dry plaster. The paints used can e.g. be casein paint, tempera, oil paint, silicate mineral paint. If the pigments are mixed with lime water or lime milk and applied to a dry plaster the technique is called lime secco painting. The secco technique contrasts with the fresco technique, where the painting is executed on a layer of wet plaster.

Silicate mineral paints or mineral colors are paint coats with mineral binding agents. Two relevant mineral binders play a role in the field of colors: Lime and silicate.

<span class="mw-page-title-main">Sinopia</span> Dark reddish-brown natural earth pigment

Sinopia is a dark reddish-brown natural earth pigment, whose reddish colour comes from hematite, a dehydrated form of iron oxide. It was widely used in Classical Antiquity and the Middle Ages for painting, and during the Renaissance it was often used on the rough initial layer of plaster for the underdrawing for a fresco. The word came to be used both for the pigment and for the preparatory drawing itself, which may be revealed when a fresco is stripped from its wall for transfer.

<span class="mw-page-title-main">Sittanavasal Cave</span> Historic site in Pudukottai, India

Sittanavasal Cave is a 2nd-century Tamil Śramaṇa complex of caves in Sittanavasal village in Pudukottai district of Tamil Nadu, India. Its name is a distorted form of Sit-tan-na-va-yil, a Tamil word which means "the abode of great saints".

<span class="mw-page-title-main">Restoration of the Sistine Chapel frescoes</span> 20th-century art conservation project

The conservation-restoration of the frescoes of the Sistine Chapel was one of the most significant conservation-restorations of the 20th century.

<span class="mw-page-title-main">Cleaning agent</span> Substance used to remove dirt or other contaminants

Cleaning agents or hard-surface cleaners are substances used to remove dirt, including dust, stains, foul odors, and clutter on surfaces. Purposes of cleaning agents include health, beauty, removing offensive odor, and avoiding the spread of dirt and contaminants to oneself and others. Some cleaning agents can kill bacteria and clean at the same time. Others, called degreasers, contain organic solvents to help dissolve oils and fats.

<span class="mw-page-title-main">Conservation and restoration of ceramic objects</span> Preservation of heritage collections

Conservation and restoration of ceramic objects is a process dedicated to the preservation and protection of objects of historical and personal value made from ceramic. Typically, this activity of conservation-restoration is undertaken by a conservator-restorer, especially when dealing with an object of cultural heritage. Ceramics are created from a production of coatings of inorganic, nonmetallic materials using heating and cooling to create a glaze. These coatings are often permanent and sustainable for utilitarian and decorative purposes. The cleaning, handling, storage, and in general treatment of ceramics is consistent with that of glass because they are made of similar oxygen-rich components, such as silicates. In conservation ceramics are broken down into three groups: unfired clay, earthenware or terracotta, and stoneware and porcelain.

Conservation-restoration of Leonardo da Vincis <i>The Last Supper</i>

Work on the conservation and restoration of Leonardo da Vinci's The Last Supper mural, much of it more harmful than helpful, has been carried out over many centuries, and continues. Completed in the late 15th century by the Renaissance artist Leonardo da Vinci, the mural is located in the refectory of the Convent of Santa Maria delle Grazie, Milan, Italy. The Last Supper was commissioned by Ludovico Sforza, Duke of Milan in 1495, as part of a series of renovations to the convent with the intention that the location would become the Sforza family mausoleum. Painting began in 1495 and continued until 1498.

<span class="mw-page-title-main">Conservation and restoration of paintings</span> Preservation of heritage collections

The conservation and restoration of paintings is carried out by professional painting conservators. Paintings cover a wide range of various mediums, materials, and their supports. Painting types include fine art to decorative and functional objects spanning from acrylics, frescoes, and oil paint on various surfaces, egg tempera on panels and canvas, lacquer painting, water color and more. Knowing the materials of any given painting and its support allows for the proper restoration and conservation practices. All components of a painting will react to its environment differently, and impact the artwork as a whole. These material components along with collections care will determine the longevity of a painting. The first steps to conservation and restoration is preventive conservation followed by active restoration with the artist's intent in mind.

The conservation and restoration of ancient Greek pottery is a sub-section of the broader topic of conservation and restoration of ceramic objects. Ancient Greek pottery is one of the most commonly found types of artifacts from the ancient Greek world. The information learned from vase paintings forms the foundation of modern knowledge of ancient Greek art and culture. Most ancient Greek pottery is terracotta, a type of earthenware ceramic, dating from the 11th century BCE through the 1st century CE. The objects are usually excavated from archaeological sites in broken pieces, or shards, and then reassembled. Some have been discovered intact in tombs. Professional conservator-restorers, often in collaboration with curators and conservation scientists, undertake the conservation-restoration of ancient Greek pottery.

The conservation and restoration of Pompeian frescoes describes the activities, methods, and techniques that have historically been and are currently being used to care for the preserved remains of the frescoes from the archeological site of Pompeii, Italy. The ancient city of Pompeii is famously known for its demise in A.D. 79 after the fatal eruption of Mount Vesuvius wiped out the population and buried the city beneath layers of compact lava material. In 1738, King Charles III or Charles of Bourbon, began explorations in Portici, Resina, Castellammare di Stabia, a Civita, where it was believed that the ancient cities of Pompeii, Stabiae, and Herculaneum were buried beneath. The first phase of the excavations at Pompeii started in 1748, which led to the first conservation and restoration efforts of the frescoes since their burial, and in 1764, open-air excavations began at Pompeii. Pompeii has a long history of excavation and restoration that began without a strong foundation or strategy. After centuries of cronyism, recurring financial shortages, and on-again-off-again restoration, the city's frescoes and structures were left in poor condition. In 1997, Pompeii was added to the UNESCO List of World Heritage Sites.

<span class="mw-page-title-main">Mineral painting</span> Technique of fresco preparation and painting

Mineral painting or Keim's process, also known as stereochromy, is a mural or fresco painting technique that uses a water glass-based paint to maximize the lifetime of the finished work.

References

  1. 1 2 Gardinali, Piero R. "Chemistry and Fresco Painting". Archived 2016-03-04 at the Wayback Machine Florida International University. Retrieved 19 November 2015
  2. Douma, Michael and Juraj Lipscher. "Pigments through the Ages". WebExhibits. Retrieved 21 November 2015.
  3. 1 2 Garg, K.L; Jain, Kamal; Mishra, A.K (1995). "Role of Fungi in the Deterioration of Wall Paintings" (PDF). The Science of the Total Environment. 167 (1–3): 255–271. Bibcode:1995ScTEn.167..255G. doi:10.1016/0048-9697(95)04587-q. Archived from the original (PDF) on 13 August 2017. Retrieved 2 December 2015.
  4. Ciferri, Orio (March 1999). "Microbial Degradation of Paintings". Applied and Environmental Microbiology. 65 (3): 879–885. Bibcode:1999ApEnM..65..879C. doi:10.1128/AEM.65.3.879-885.1999. PMC   91117 . PMID   10049836.
  5. Garg, K.L; Kaml, Jain; Mishra, A.K (1995). "Role of Fungi in the Deterioration of Wall Paintings" (PDF). The Science of the Total Environment. 167 (1–3): 255–271. Bibcode:1995ScTEn.167..255G. doi:10.1016/0048-9697(95)04587-q. Archived from the original (PDF) on 2017-08-13. Retrieved 2015-12-07.
  6. Merello, P.; Garcia-Diego, F.; Zarzo, M. (2012). "Microclimate Monitoring of Aridane's House (Pompeii, Italy) for Preventive Conservation of Fresco Painting". Chemistry Central Journal. 6 (145): 145. doi: 10.1186/1752-153X-6-145 . PMC   3541997 . PMID   23190798.
  7. 1 2 3 4 Brazil, Rachel. "Conservative Innovations". Chemistryworld. Royal Society of Chemistry. Retrieved 7 December 2015.
  8. Nocentini, Serena. "'Strappo' Detachment". Museo Benozzo Gozzoli. Archived from the original on 25 February 2016. Retrieved 7 December 2015.
  9. Avvisati, Carlo; McGivern, Hannah. "Pompeian Frescoes Cured with Antibiotics". The Art Newspaper. Retrieved 7 December 2015.
  10. Cacci., ed, Leonardo (2003). La Fenice Reconstructed 1996-2003: A Building Site. Venezia: Marsilio. p. 118.{{cite book}}: |last1= has generic name (help)
  11. "Sistine Chapel Restoration Controversy". APECSEC.org. Retrieved 7 December 2015.
  12. Lobell, Jaretta A. "Saving the Villa of the Mysteries". Archaeology Magazine. Archaeology Institute of America. Retrieved 1 December 2015.
  13. Avvisati, Carlo; McGivern, Hannah. "Pompeian Frescoes Cured with Antibiotics". The Art Newspaper. Retrieved 7 December 2015.