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Conservation concept for the treatment of biologically induced encrustations and formation of tufa

 The eastern Naiad fountain in the gardens of Schönbrunn Palace
Martina Haselberger

Abstracts

The sculpture of the eastern Naiad Fountain at Schönbrunn made of white marble is covered with calcareous encrustations and secondary grown tufa. These biologically induced accretions influence its actual appearance significantly. Examinations of structure and composition of the crusts and tufa, and the inhabiting organisms responsible for the precipitation, as well as, considerations of historic issues enable the development of a concept for the conservation.

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The author would like to thank Prof. Gabriela Krist, head of the Institute of Conservation, and Mag. Marija Milchin for their supervision and support. Further thanks go to Prof. Johannes Weber (Department of Conservation Sciences, University of Applied Arts Vienna), Prof. Katja Sterflinger (Institute of Biotechnology, BOKU Vienna) and Prof. Andreas Rohatsch (Institute of Geotechnics, Technical University Vienna) for performing the examinations and the Schönbrunn Schloss- und Kulturbetriebsges.m.b.H. for providing the object of this research.

Introduction

1The eastern Naiad Fountain is one of the few fountains in the gardens of Schönbrunn Palace that has not been restored yet. Built in the 18th century, the fountain consists of sculptures made of marble situated in the centre of a round pool. As a result of missing maintenance in the last decades calcareous encrustations have formed on the whole surface as a result of metabolic processes of organisms. Additionally, the formation of tufa on the front side of the fountain sculpture can be observed. These secondary accretions significantly affect the actual appearance of the Naiad Fountain and harmful effects on the marble cannot be ruled out.

Fig. 1 Eastern Naiad Fountain

Fig. 1 Eastern Naiad Fountain

Eastern Naiad Fountain in the gardens of Schönbrunn Palace (Vienna)

Credits Martina Haselberger © Institute of Conservation, University of Applied Arts Vienna.

  • 1  Research and analyses were conducted in the framework of the diploma thesis of the author at the I (...)

2In order to define a concept for the conservation, the question of how these secondary accretions should be treated from a restorer’s point of view has to be considered. Scientific analyses provide information about the encrustations and the organisms inhabiting the Naiad Fountain, and assist in understanding the factors influencing the formation of crusts and tufa. Additionally, historic considerations are incorporated in the decision1.

The eastern Naiad Fountain

3The eastern Naiad Fountain in the gardens of the imperial residence Schönbrunn Palace in Vienna was erected as part of a redesign of the gardens in the 18th century under the reign of the Empress Maria Theresia. During this time also other important fountains like the Neptune Fountain, the Obelisk Fountain, the Roman Ruin, the Fair Spring and the western Naiad Fountain were built (IBY 2007: 12). The Naiad Fountain is situated in the centre of the intersection of a star-shaped system of avenues and is surrounded by eight large marble vases sculpted by Johann Baptist Hagenauer.

  • 2  Sterzing marble is a coarse-crystalline metamorphic marble almost entirely composed of calcite. It (...)

4The round pool embedded in the ground was placed at its current position in 1772 (HAJOS 1995:30). Next to the central Naiad sculpture are eight accumulations of earth and stone fragments acting as anchor points for the water lilies. The sculpture is made of the white Sterzing marble2 and represents a Naiad, a nymph of springs and steams, playing with a putto and a waterbird. A water fountain comes out of the bird’s beak and two stylised shells are placed next to the group of figures (ill.1).

5The sculpture was created between 1777-1780 by the German sculptor Johann Christian Wilhelm Beyer (HAJOS 1995:146). Most of the other sculptures in the garden are attributed to him and his workshop (HAJOS 2004:33).

Condition survey and former restorations

  • 3  See photos in the archive of Schönbrunn Schloss- und Kulturbetriebsges.m.b.H, Austrian Federal Off (...)
  • 4  Since 1976 no treatments were conducted according to Ing. Gerhard Drucker, technical director of S (...)

6Regarding previous conservation treatments, one extensive intervention can be dated to the years after World War II3. The measures conducted in this time include the complete renovation of the pool, the dismantling of the sculpture, the erection of a new basement made of concrete and its reassembling. Up to 1976, only smaller conservation measures have been proven by photos4.

7In order to simulate a grotto-like foundation and to hide the basement itself, the concrete basement of the sculpture is surrounded by stone fragments and spolia. The sculpture is made of the white Sterzing marble and consists of several parts. Two stone indents – the arm of the putto and the arm of the naiad – and a metal tube for the water fountain were added as part of the restoration in the 1950s.

  • 5  For further information on the condition refer to HASELBERGER 2014.

8As a result of high humidity caused by the fountain situation, former treatments, and the outdoor position, different damage have occurred. Besides surface soiling (bird droppings, pollution from the surrounding area), biological growth, different forms of joint damage (e. g. cracks, lost adhesion of the joint mortar, use of too hard and too dense materials for the joints), breaks and hairline cracks, several sculptural details are missing5.

9Regarding the current condition the focus is on the biological growth and the biologically induced formation of encrustations and tufa, as these phenomena significantly influence the sculpture’s actual appearance.

Biological growth and formation of encrustations and tufa

10Generally, the Naiad Fountain offers good conditions for biological growth and encourages an extensive colonisation of the surfaces. Water – used by the organisms for their metabolism and to maintain their functions (CANEVA 1991:11) – is sufficiently available due to the outdoor position. Light is predominantly used as an energy source from organisms performing photosynthesis (MADIGAN 2006:604ff.), and is also not limiting biological growth in this case. Even though, the fountain is situated in Austria’s capital, air pollution is relatively low and the most important nutrients including phosphorus, carbon, oxygen, hydrogen, nitrogen, sulphur, calcium, magnesium and sodium can be taken out of the pool or from its surroundings (CANEVA 2008). As a result there are biofilms of differing thickness, composition, and appearance covering the whole surface of the fountain.

Fig.2 Greyish encrustations and tufa

Fig.2 Greyish encrustations and tufa

Greyish encrustations on the whole surface and formation of tufa at the front side of the sculpture.

Credits Martina Haselberger © Institute of Conservation, University of Applied Arts Vienna.

  • 6  The identification and microscopic examination were performed by the author and Assoc. Prof. Dr. K (...)
  • 7  Poikilohydre plants can adjust their water content to the surrounding area. They are able to survi (...)

11In cooperation with the University of Natural Resources and Life Sciences in Vienna the inhabiting microorganisms were determined6. In the samples taken from different areas of the sculpture, filamentous and coccoid cyanobacteria, algae, moss, and lichens have been identified. These organisms are phototrophic and poikilohydric7 – properties facilitating their growth on the fountain.

  • 8  Information provided by Assoc. Prof. Dr. Katja Sterflinger, Institute of Biotechnology, BOKU Vienn (...)

12Remarkably, the organisms have adapted vividly to the availability of light and humidity. For example, cyanobacteria inhabiting surfaces exposed to strong sunlight show a stronger pigmentation with scytonemin8 in the upper layers of the biofilm than in lower ones. Elsewhere they have transferred their growth into the inside of the marble, where they are protected from the harmful UV radiation (CANEVA 2008:44), but still get enough light due to the translucency of the marble grains (compare ill.7).

13In areas with constant water supply through the water fountain and a high humidity, algae and moss are predominantly found, while cyanobacteria and lichens grow in areas that frequently dry out (HASELBERGER 2014:76f.). Cyanobacteria, algae, and moss inhabiting the Naiad Fountain are also responsible for a highly interesting phenomenon: the formation of encrustations and tufa.

  • 9  Examination and SEM measurements were performed by ao. Univ.-Prof. Dr. Johannes Weber, Department (...)

14While the former cover the whole surface of the sculpture, the tufa can only be found at the front side of the naiad overgrowing sculptural details (ill.2). To clarify questions about composition, structure, adhesion to the marble surface, and mechanisms of formation thin-sections of samples were prepared and examined under both light and scanning electron microscope9.

15Both secondary accretions mainly consist of calcium carbonate. The encrustations are few millimetres thin and show a layered structure. The single layers differ in thickness and porosity and there are local differences in sequence and in number of the layers (ill.3). By comparing the stratigraphy of the samples, similar layers and recurring sequences can be determined. The sequence of the layers is probably correlating with former cleaning measures, but as there are no written documents about the maintenance of the sculpture, no precise conclusions can be drawn.

Fig.3  Thin-section image of the crust

Fig.3  Thin-section image of the crust

 Sample taken from the Putto’s arm showing several layers differing in thickness and porosity; blue areas correspond to cavities as the resin for embedding was coloured; polarization microscope, transmitted light.

Credits ao.Univ.-Prof. Dr. phil. Johannes Weber, Department of Conservation Sciences, University of Applied Arts Vienna.

  • 10  The tufa grown on the Naiad Fountain has to be differentiated from travertine, as no geological pr (...)

16In contrast to the encrustations, the tufa10 shows a more porous structure and no layering. Vegetative forms like leaf deposits are partially visible within the thin-section (ill.4).

Fig. 4  Cross section of the tufa

Fig. 4  Cross section of the tufa

Thin-section image, stereomicroscope, transmitted light.

Credits ao. Univ.-Prof. Dr. phil. Johannes Weber, Department of Conservation Sciences, University of Applied Arts Vienna.

17Microorganisms or traces of former organisms (e.g. outline of a leaf) can be found in samples taken from the encrustations and the tufa (compare ill.4). Furthermore, precipitated calcium carbonate is embedded in the bacterial mucilage (ill.5). These facts indicate that the formation is biologically induced (RIDING 2011:636). Thus, the precipitation of the calcium carbonate is based on metabolic processes of the inhabiting organisms. The crystal habits and properties of such minerals are similar to those of minerals precipitated under chemical conditions (KONHAUSER 2012: 105).

Fig.5 SEM-SE micrograph of the crust

Fig.5 SEM-SE micrograph of the crust

The SEM-SE (scanning electron microscope using the secondary image (SE) detector) image shows microorganisms covered with mucilage and precipitated calcium carbonate.

Credits ao. Univ.-Prof. Dr. phil. Johannes Weber, Department of Conservation Sciences, University of Applied Arts Vienna.

18Generally, cyanobacteria and algae are responsible for the calcareous encrustations, while moss encourages the formation of tufa (BAIER 2002, RIDING 2011:636). In both cases the accretions can be described as a kind of encrusted biofilms. The mechanisms of their consolidation may be quite simple. For example, small mineral grains may get trapped in the root system of the organisms or they get stuck to the sticky surface of their mucilage (BOLIVAR 1997: 214).

19In addition, the organisms are also able to influence the precipitation of calcium carbonate and the formation of crusts by more complex processes. As the surface of biofilms is charged negatively it encourages the adhesion of cations from the water (especially Ca2+) (KONHAUSER RIDING 2012:17; SHIRAISHI 2008: 51). As a result of the photosynthesis, organisms change the pH value of the water and, consequently, also the ionic concentration in favour of an enrichment of anions (carbonate ions). They form complexes with the cations on the biofilm’s surface which leads to a precipitation of calcium carbonate on the cell surface and the organisms cover themselves with a thin calcareous layer (KONHAUSER 2012: 109). Regarding the formation of tufa the organisms often die underneath the crust and new organisms colonize the surface (BAIER 2002).

  • 11  Examples for the growth of tufa in nature may be seen at the “Steinerne Rinne” in Germany or the P (...)

20On the one hand, the formation of encrustations on fountains made of stone is quite common. On the other hand, the growth of porous tufa occurs rarely, although, it is a widespread phenomenon in natural areas situated alongside waterfalls and steams (CANEVA 2008:82)11. In the course of the research only two references for similar tufa formations on fountains could be determined: the Roman Ruin in the gardens of Schönbrunn Palace in Vienna (Austria) and the Fontana dei Draghi in the Villa d’Este in Tivoli (Italy).

Treatment of encrustations and tufa on the Naiad Fountain

21The encrustations and the tufa have a significant influence on the current condition and appearance of the Naiad Fountain. Due to embedded fly ash, particles of dust, or different forms of air pollution the encrustations have a greyish colour. The sculpture made of white marble appears in a completely different colour which affects the legibility of the monument and complicates the determination of the materiality. Additionally, the tufa has already overgrown parts of the sculpture which are not visible any more (compare ill.2).

22It is, therefore, important to decide how these secondary accretions should be treated. From the restorer’s point of view the preservation of the original substance has to be the focus. Therefore, the main aim of the conducted analyses and research has been to clarify if the encrustations and the tufa, as well as, the biological colonization protect or harm the marble.

23On the one hand, the encrustations and the tufa act as a kind of “sacrificial layer” for the marble underneath and protect it from erosion, pollution, and solution processes.

24On the other hand, in situ investigations revealed a weathering process induced by the encrustations. On surfaces exposed to strong sunlight the crusts flake off together with the first grain layers of the marble which means a loss of original substance (ill.6). This flaking can be explained by the differing coefficients of thermal expansion of the white marble and the dark crust. Furthermore this kind of uncovering promotes further damage as the properties of the exposed marble surface and the surface of the dark crust vary regarding moisture absorption and thermal expansion.

Fig. 6 Crust flakes off together with the first grain layers of the marble

Fig. 6 Crust flakes off together with the first grain layers of the marble

Probably due to the differing coefficients of thermal expansion of the white marble and the dark crust.

Credits Martina Haselberger, © Institute of Conservation, University of Applied Arts Vienna.

  • 12  Information regarding biodeterioration gained from following literature: ALLSOPP 2004, WARSCHEID 2 (...)

25Crusts can also influence moisture transfer and lead to an accumulation of humidity between the stone surface and the crusts (ROHATSCH 2004). Additionally, biological growth is favoured due to the moisture retention and the rough surface of the crusts, and biological weathering is accelerated12.

26At the Naiad Fountain the inhabiting organisms have already contributed to the biodeterioration actively. As a result of the production of acids the organisms dissolve the marble surface (BOCK 1991). They etch the surface and drill channels into the marble grains (ill.7).  

Fig. 7  Thin-section image of the etched marble surface and the canals drilled by the microorganisms

Fig. 7  Thin-section image of the etched marble surface and the canals drilled by the microorganisms

Blue areas correspond to cavities as the resin for embedding was coloured; polarization microscope, incident light.

Credits ao. Univ.-Prof. Dr. phil. Johannes Weber, Department of Conservation Sciences, University of Applied Arts Vienna.

  • 13  The existing tufa with thicknesses of 10 cm has grown within 60 years.

27Obviously, the optical and aesthetical impairment of the crusts and tufa have to be considered as well. Furthermore, the Naiad sculpture will be continuously overgrown by the quickly growing tufa13.

  • 14  The SKB was founded in 1992 and is responsible for the administration of the palace and related si (...)

28As the encrustations, the tufa, and the biological growth itself harm and protect the original substance equally, other historic and conservation aspects have been considered. The Schönbrunner Schloss- und Kulturbetriebsges.m.b.H. (SKB)14 formulated an overall conservation concept for the palace and its garden which aims to restore them to their original appearance during the reign of Empress Maria Theresia (WEHDORN 2002).

29The main fountains in the garden of Schönbrunn were built within the same period and designed according to an overall concept. This master plan envisages white sculptures – made of marble or of other stone painted with white colour - on a grotto-like foundation (GHAFFARI 2005). Therefore, all fountains are part of the ensemble and cannot be treated individually. Thus, conservation concepts and treatments of other fountains in Schönbrunn must be taken into consideration. All of them aimed at following the overall conservation concept formulated by the SKB and included the complete uncovering of the sculptures, the removing of existing encrustations (ill.8), or the re-application of the former white paint. In contrast to the other optically compatible fountains the Naiad Fountain stands out significantly.

Fig. 8 Sculpture of the Roman Ruin in Schönbrunn

Fig. 8 Sculpture of the Roman Ruin in Schönbrunn

Condition after the conservation treatment in 2013 which included the uncovering of the marble surface.

Credits Martina Haselberger, © Institute of Conservation, University of Applied Arts Vienna.

Aim and concept of the conservation

  • 15  These include different mechanical abrasive methods like chisel, micro-chisel and sandblasting wit (...)

30After considering all these aspects the concept for the conservation of the Naiad Fountain considers the removal of the encrustations and the tufa in order to restore its original appearance. In order to fulfill this aim it had to be clarified if this removal is possible, while preserving the original marble surface. Therefore, test areas were executed and different methods were evaluated15. As expected sandblasting was the best method to remove the crusts using glass beads as the favoured material (ill.9). The tufa was easily removed with hammer and chisel (ill.10).

Fig. 9 Test area

Fig. 9 Test area

Removing of the crust with sandblasting.

Credits Martina Haselberger, © Institute of Conservation, University of Applied Arts Vienna.

Fig. 10 Test area

Fig. 10 Test area

After the removal of the tufa.

Credits Martina Haselberger, © Institute of Conservation, University of Applied Arts Vienna.

31The final conservation concept is based on results of the examinations and on the experiences gained during previous conservation campaigns and evaluations conducted by the Institute of Conservation (University of Applied Arts Vienna) in the garden of Schönbrunn Palace from 2005 to 2013 (WEIXELBAUMER 2006; SPORNBERGER 2007; GRÄBER 2005; PRSKALO 2013).

  • 16  For the consolidation silicic acid ethyl ester with bonding agents for lime based stones is recomm (...)

32The concept considers the high humidity and the outdoor position of the sculpture and the single measures are specifically tailored to the requirements of the monument. Thus, it is generally recommended to use consolidants and binders based on inorganic materials and to avoid organic binders16.  The reason for this is that some organic binders are not very stable in areas with permanent humidity as they start swelling, they may reduce water release while water adsorption remains the same (ROHATSCH 1999:136), or they can be used as nutrients by organisms (ALESSANDRINI 1995:1-20). Regarding fills stone idents should be preferred. For small lacunae mortars based on inorganic binders are generally recommended. As the use of organic binders allows a better imitation of the translucent appearance of the white marble, they can be used in a moderate way and in small parts to enable a better integration.

33Additionally, a maintenance concept has been formulated. This should reduce a fast re-colonisation of the marble surface and prevent the resulting formation of encrustations after the conservation. In case of outdoor fountains it is not possible to prevent biological growth completely, but a regular maintenance is important to prevent the formation of crusts and tufa. A regular, weekly cleaning of the water in the pool, which includes the removal of leafs and dirt, as well as, the complete change of the water once a year are recommended. These measures contribute to the reduction of nutrients in the water and subsequently inhibit biological growth. The sculpture itself should be cleaned with cold water and brushes once a year to prevent the formation of dense and hardly removable biofilms, which result in the formation of crusts.

Conclusion

34In order to define conservation measures for the eastern Naiad Fountain it was necessary to clarify how the secondary accretions on the sculpture should be treated from a restorer’s point of view. First, the harmful and protective effects of the encrustation and the tufa on the marble were discussed. Scientific analyses provide insightful results about the structure, composition, and adhesion of the crusts and the tufa to the marble surface. The current condition of the marble is quite good, although, the surface shows some damage due to biological weathering in form of solution and etching. Furthermore, the crusts are responsible for the loss of original substance as they flaked off together with the first layers of the marble visible during the in-situ monitoring. The aesthetical and optical impairment induced by the dark encrustations and the tufa were considered as well.  

35Besides these aspects, conservation and historical issues were integrated into the decision-making process. The overall conservation concept for the garden of Schönbrunn Palace and the original design concept – white sculpture on a grotto-like foundation – required the consideration of the actual appearance of the other fountains in Schönbrunn and the discussion on their previous treatments. The formulated concept for the conservation is based on the experiences and results from former conservation measures conducted by the Institute of Conservation and responds to the individual requirements of the Naiad Fountain. The recommended measures were tested and could be executed in test areas while maintaining the original substance. The approach can also be used as a model for other fountains with similar problems.

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Notes

1  Research and analyses were conducted in the framework of the diploma thesis of the author at the Institute of Conservation, University of Applied Arts Vienna under the supervision of Prof. Gabriela Krist from 2013 to 2014.

2  Sterzing marble is a coarse-crystalline metamorphic marble almost entirely composed of calcite. It was quarried near the town of Sterzing in South Tyrol and used for constructions and carvings for a long period. The heyday of its use was before the end of the 18th century. (WEBER 2007:2; ROHATSCH 1999:133; RÜDRICH 2003)

3  See photos in the archive of Schönbrunn Schloss- und Kulturbetriebsges.m.b.H, Austrian Federal Office for the Care of Monuments Austria and Austrian National Library.

4  Since 1976 no treatments were conducted according to Ing. Gerhard Drucker, technical director of SKB, oral message.

5  For further information on the condition refer to HASELBERGER 2014.

6  The identification and microscopic examination were performed by the author and Assoc. Prof. Dr. Katja Sterflinger, Institute of Biotechnology, BOKU Vienna. The SEM measurement on one sample was performed by ao. Univ.-Prof. Dr. Johannes Weber, Department of Conservation Sciences, University of Applied Arts Vienna.

7  Poikilohydre plants can adjust their water content to the surrounding area. They are able to survive fluctuations in humidity and periods of complete dryness (Lexikon der Biologie, online version).

8  Information provided by Assoc. Prof. Dr. Katja Sterflinger, Institute of Biotechnology, BOKU Vienna.

9  Examination and SEM measurements were performed by ao. Univ.-Prof. Dr. Johannes Weber, Department of Conservation Sciences, University of Applied Arts Vienna.

10  The tufa grown on the Naiad Fountain has to be differentiated from travertine, as no geological processes are included in its formation. The consolidation of the tufa on the fountain takes place without the influence of high pressure or temperature (Personal communication from ao. Univ.-Prof. Mag. Dr. Andreas Rohatsch, Institute of Geotechnics, Research Center for Engineering Geology, Technical University Wien, 19.8.2013).

11  Examples for the growth of tufa in nature may be seen at the “Steinerne Rinne” in Germany or the Plitvice Lakes in Croatia.

12  Information regarding biodeterioration gained from following literature: ALLSOPP 2004, WARSCHEID 2000 and 2008, CANEVA 2008 and SCHERRER 2009.

13  The existing tufa with thicknesses of 10 cm has grown within 60 years.

14  The SKB was founded in 1992 and is responsible for the administration of the palace and related sites. It aims to acquire funds for renovation and maintenance and to protect the sites.

15  These include different mechanical abrasive methods like chisel, micro-chisel and sandblasting with different blasting materials and varying pressure.

16  For the consolidation silicic acid ethyl ester with bonding agents for lime based stones is recommended (HASELBERGER 2014:122), for the fills a lime-cement mix can be used.

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List of illustrations

Title Fig. 1 Eastern Naiad Fountain
Caption Eastern Naiad Fountain in the gardens of Schönbrunn Palace (Vienna)
Credits Credits Martina Haselberger © Institute of Conservation, University of Applied Arts Vienna.
URL http://journals.openedition.org/ceroart/docannexe/image/4944/img-1.jpg
File image/jpeg, 1.0M
Title Fig.2 Greyish encrustations and tufa
Caption Greyish encrustations on the whole surface and formation of tufa at the front side of the sculpture.
Credits Credits Martina Haselberger © Institute of Conservation, University of Applied Arts Vienna.
URL http://journals.openedition.org/ceroart/docannexe/image/4944/img-2.jpg
File image/jpeg, 936k
Title Fig.3  Thin-section image of the crust
Caption  Sample taken from the Putto’s arm showing several layers differing in thickness and porosity; blue areas correspond to cavities as the resin for embedding was coloured; polarization microscope, transmitted light.
Credits Credits ao.Univ.-Prof. Dr. phil. Johannes Weber, Department of Conservation Sciences, University of Applied Arts Vienna.
URL http://journals.openedition.org/ceroart/docannexe/image/4944/img-3.jpg
File image/jpeg, 1.0M
Title Fig. 4  Cross section of the tufa
Caption Thin-section image, stereomicroscope, transmitted light.
Credits Credits ao. Univ.-Prof. Dr. phil. Johannes Weber, Department of Conservation Sciences, University of Applied Arts Vienna.
URL http://journals.openedition.org/ceroart/docannexe/image/4944/img-4.jpg
File image/jpeg, 2.5M
Title Fig.5 SEM-SE micrograph of the crust
Caption The SEM-SE (scanning electron microscope using the secondary image (SE) detector) image shows microorganisms covered with mucilage and precipitated calcium carbonate.
Credits Credits ao. Univ.-Prof. Dr. phil. Johannes Weber, Department of Conservation Sciences, University of Applied Arts Vienna.
URL http://journals.openedition.org/ceroart/docannexe/image/4944/img-5.jpg
File image/jpeg, 360k
Title Fig. 6 Crust flakes off together with the first grain layers of the marble
Caption Probably due to the differing coefficients of thermal expansion of the white marble and the dark crust.
Credits Credits Martina Haselberger, © Institute of Conservation, University of Applied Arts Vienna.
URL http://journals.openedition.org/ceroart/docannexe/image/4944/img-6.jpg
File image/jpeg, 648k
Title Fig. 7  Thin-section image of the etched marble surface and the canals drilled by the microorganisms
Caption Blue areas correspond to cavities as the resin for embedding was coloured; polarization microscope, incident light.
Credits Credits ao. Univ.-Prof. Dr. phil. Johannes Weber, Department of Conservation Sciences, University of Applied Arts Vienna.
URL http://journals.openedition.org/ceroart/docannexe/image/4944/img-7.jpg
File image/jpeg, 796k
Title Fig. 8 Sculpture of the Roman Ruin in Schönbrunn
Caption Condition after the conservation treatment in 2013 which included the uncovering of the marble surface.
Credits Credits Martina Haselberger, © Institute of Conservation, University of Applied Arts Vienna.
URL http://journals.openedition.org/ceroart/docannexe/image/4944/img-8.jpg
File image/jpeg, 792k
Title Fig. 9 Test area
Caption Removing of the crust with sandblasting.
Credits Credits Martina Haselberger, © Institute of Conservation, University of Applied Arts Vienna.
URL http://journals.openedition.org/ceroart/docannexe/image/4944/img-9.jpg
File image/jpeg, 792k
Title Fig. 10 Test area
Caption After the removal of the tufa.
Credits Credits Martina Haselberger, © Institute of Conservation, University of Applied Arts Vienna.
URL http://journals.openedition.org/ceroart/docannexe/image/4944/img-10.jpg
File image/jpeg, 1.5M
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References

Electronic reference

Martina Haselberger, « Conservation concept for the treatment of biologically induced encrustations and formation of tufa », CeROArt [Online], EGG 5 | 2016, Online since 17 March 2016, connection on 18 December 2017. URL : http://journals.openedition.org/ceroart/4944

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About the author

Martina Haselberger

Martina Haselberger, graduated in 2014 with Mag. art. degree in stone conservation from Institute of Conservation, University of Applied Arts Vienna. martina.haselberger@uni-ak.ac.at

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Copyright

Licence Creative Commons
CeROArt – Conservation, exposition, restauration d'objets d'arts est mis à disposition selon les termes de la licence Creative Commons Attribution - Pas d'Utilisation Commerciale - Pas de Modification 4.0 International.

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