DEALING WITH AUTHENTICITY IN THE CONSERVATION AND RESTORATION OF WALL PAINTINGS AND ARCHITECTURAL SURFACES

Authenticity is a key term in the modern theory and practice of heritage preservation. The great influence of this term began with the Venice Charter and increased in the following decades until this day, as numerous documents and publications have dealt with issues concerning the concept and significance of authenticity. However, the term is characterized by a certain vagueness, despite its central role in the international debate. This article presents three case studies related to the conservation-restoration of wall paintings and architectural surfaces in Germany and Italy and uses them to clarify some central theoretical issues, intertwining them with practical needs and demands. The multi-layered meanings of authenticity in the practice of conservation-restoration can range from the respectful preservation of the handed-on conditions and appearance of a work, with all material remains of its reception and interpretation, to the critical evaluation of historical restorations based on scholarly value judgments, and even to the reconstruction e. g. of architectural surfaces as a method for the sustainable protection of historical findings and a good way to visualize historical presentations and hand on traditions of craftmanship. For such a broad spectrum of meanings, the term authenticity can become a helpful umbrella term in interdisciplinary and transdisciplinary communication, well-known and appreciated by all experts and by the public. In order to avoid the use of the term authenticity as a catch-all that can mean everything or nothing, the relationship with case studies can bring awareness about the broad palette of these approaches and how the theory and practice of heritage preservation are always interconnected.


Introduction
Authenticity is a key term in the modern theory and practice of heritage preservation, as emphasized in the introduction of the Venice Charter's statement on historic monuments: "It is our duty to hand them on in the full richness of their authenticity". (The Venice Charter, 1964) In fact, the great influence of this term began with this remarkable statement of 1964, because "authenticity" in previous theoretical treatises on the preservation and conservation-restoration of cultural heritage held only a marginal significance, in comparison e. g. with the central discussion on the definition of the term "original" in its artistic and historical significance (see e.g. Brandi, 1963). In his essay "Authenticity? The dogma of self-delusion" David Lowenthal outlines this phenomenon: "The cult of authenticity pervades modern life. Titles of publications with the words 'authentic' , 'authenticity' and 'authentication' have multiplied fivefold since the 1970s. All arts agree on the need to be authentic, if on nothing else", and he analyses the multi-layered historical, social and psychological aspects of authenticity with amusing and astonishing but in any case, meaningful examples (Lowenthal, 1992, quotation p. 184). Published twenty years after the Venice Charter, the Nara Document on Authenticity (The Nara Document,1994) offers essential support for a comprehensive understanding of the complex meanings of authenticity, against the risks of levelling in a globalized world. Refusing every kind of normative definition of authenticity, the Nara Document claims respect for different cultures and regions of the world with their specific traditions of preservation of cultural heritage. It highlights the precondition of gaining knowledge from all information sources as an essential basis for assessing all aspects of authenticity. Already one year before, in 1993, Wilfried Lipp had argued against a reduced and unilateral understanding of the term authenticity, as often practised by historical science, with its exclusive assessment on "facts" and without consideration of the transitory character of historical monuments in their time-bound reception and transformation (Lipp, 1993). Authenticity is a challenging term closely connected to conservation ethics today, characterized both by high expectations and, at the same time, by a kind of "shimmering vagueness". In his publication with the felicitous title Schillernde Unschärfe 1 , Tino Mager gives a comprehensive analysis of the multifaceted term authenticity with its etymology and its meanings over the course of time, in reference to historical monuments (Mager, 2015). He interprets the boom of the term as a postmodern phenomenon characteristic for the disorientation of our time, connected with the desire for values such as truthfulness and genuineness without answering for their validity. The authentic is unspecific and is able to become an ideal only when the claim for universal evidence, narratives and truth begins to dissolve (Mager, 2015, p. 27). 2 In all this "shimmering vagueness", let us try to turn from theoretical statements to the real world. In the present-day practice of conservation-restoration in Europe, we need to evaluate representative case studies in order to define the multi-layered significance of authenticity for our cultural heritage, and to develop methods and techniques of how to preserve and to communicate the manifold and diverse values closely connected to this term. In the following, three case studies related to the conservationrestoration of wall paintings and architectural surfaces in Germany and Italy are presented in order to clarify some central theoretical issues in the face of practical needs and demands.

The Romanesque Wall Painting Cycle in the former Collegiate Church of Brunswick: stratification and imagination of authenticity from the mid-13th century to this day
Upon entering the monumental interior of the Romanesque Collegiate Church in Brunswick (Lower Saxony), founded by duke Henry the Lion in 1173, believers and visitors look out on the presbyterium, with the wall painting cycle in the chancel, the crossing and the transept, dated in the 1240s and signed by Johannes Wale (Gallicus). 3 It is impressive to observe the figurative scenes with their rich colouring and their ornamental framework covering walls and vaults, in harmonious interaction with the architecture. [ Fig. 1] The narration depicts the Christian history of salvation, from the prophecy of Christ's advent on earth in the Old Testament up to the eschatological vision of the Heavenly Jerusalem. (Schädler-Saub, 2000, pp. 80-84, Wolter von dem Knesebeck, 2014. Observers' distance to the monumental walls and vaults is huge and in the dark presbyterium the painting cycle is not completely discernible in all its details, but the ambiance evokes a fascinating mystic impression. This is, without any doubt, a medieval church interior handed on "in the full richness of its authenticity". Through scholarly archive studies and in situ scientific investigations related to the materials and techniques, the sequence of stratification, and the preservation status of the various painting layers, we 3 The signature preserved to this day is painted on a pillar in the main nave. Unfortunately, it is impossible to identify Johannes Wale (Gallicus) with a historically verifiable artist active in Saxony in the thirteenth century. For more detailed information on history of art and iconography, see: Wolter von dem Knesebeck, 2014. can reconstruct the literally multi-layered history of this painting cycle, from its creation in the midthirteenth century to the subsequent whitewashings and the later uncovering in 1845. This was followed by a total of three restorations in the nineteenth century, the first in 1845-54 carried out by Heinrich Brandes immediately after the uncovering, the second in 1876-1881 by August von Essenwein and the third in 1895-1898 by Adolf Quensen; the latter two involved a nearly complete over-painting. (Fig. 2) In the twentieth century, those restorations provoked a de-restoration in the 1930s by Prof. Curdt, and a re-restoration in the 1950s carried out by the conservator-restorer Fritz Herzig (Schädler-Saub, 2000, pp. 67-80). [Fig. 3] This complex history of conservation-restoration is a history of appreciation and neglect, of acclaimed rediscovery and a following series of reception and interpretation in the spirit of the respective time period, always with the goal to identify the true medieval paintings and to present them in their whole significance and beauty, i. e. in their authenticity.
The respective imagination of the authentic appearance of the painting cycle in the course of time, from the mid-nineteenth century to the 1950s, could be theoretically reconstructed by studying the documentations fortunately preserved to a large extent (see also : Hentschel & Aßmann, 2002). By looking at the tracings carried out by Brandes in 1845, in which translucid papers were applied directly on the uncovered fragmentary wall paintings, with a reintegrative drawing of the lacunae, we are able to detect some reminiscence of neo-classical style. The water colour copies designed by Adolf Quensen in 1895 show an academic assimilation of Romanesque style based on comparative studies with the numerous Romanesque wall paintings uncovered at that time. From the 1890s to this day, various documentations with black and white photos and, since the 1950s, colour photos, provide testimony to the changing appearance of the painting cycle, as a transitory work re-interpreted again and again with the imagination and expectations projected onto the handed-on wall paintings by every generation of conservator-restorers. The most curious example of a continuously evolving reception and interpretation is the transformation of the wall paintings in the conch of the main apse, from 1845 to the 1950s. [Fig. 4,5,6] Due to the very few original findings in the conch after the uncovering in 1845, Brandes opted for a simple decorative painting in neo-medieval style, instead of an impossible reconstruction of the Romanesque depiction. Adolf Quensen in 1895 rejected this solution as not conform with the spirit and the iconography of a Romanesque painting cycle. He decided to freely reconstruct the depiction of Christ in Majesty among figures of Saints. His painting was probably not based on the very poor findings still preserved in situ but referred to similar Romanesque depictions. In the 1950s, Fritz Herzig decided to perform a de-restoration of the wall paintings in the apse, not carried out in the 1930s, with a following re-restoration. In fact, Herzig reduced Quensen's painting layer and re-interpreted the underpaint layer, as well part of Quensen's work, 4 in a sober style, thus reflecting a "more Romanesque" and "more authentic" design typical for the taste of the 1950s (Schädler-Saub, 2008, pp. 145-146).  Returning to the direct observation of the wall paintings, at close range, i.e. from the scaffoldings, it is clearly visible that the paintings today are characterized by the intervention of the 1950s, with a cross hatching reintegration carried out in secco-technique that mostly covers the heterogeneous and heavily damaged historical painting layers. [ Fig. 7] Because of this, the reintegration does not respect the demands of modern conservation ethics at that time because it is not limited to the lacunae but rather spreads out like a mesh. For Fritz Herzig, this was the only way to regain the image, i. e. the visual value of the painting cycle in interrelation with the architecture, but with some misunderstandings and misinterpretations. Due to the modest investigation techniques at that time, he was not able to clearly identify the few fragments of the very delicate original tempera paintings and to distinguish them from the subsequent over-paintings. From the normal viewer distance, of course, these problems that are essential for a scholarly conservation-restoration and a well-founded analysis of history of art, are optically of no consequence. Today, we can only conserve the preservation status of the wall paintings as they have been handed on to us. 5 The aesthetic impression from a larger distance is very beautiful. Thanks to modern non-invasive investigation techniques, we can increase our knowledge about the artistic values of the medieval wall paintings and about their materials and techniques, as well as about the subsequent over-paintings. Referring to the Nara Document on Authenticity (The Nara Document, 1994), we can offer to the public a well-founded knowledge and understanding of all these sources of information related to assessing all aspects of authenticity and to appreciating this multi-layered historical authenticity and preserving it for the future. The essential significance of the history of restoration for a comprehensive understanding of the Romanesque wall painting cycle in Brunswick is not at all a singular case but rather is characteristic for many European wall paintings, even though it remains difficult to this day to implement the respect and the preservation of historical restorations. The long-time neglected values of the history of restoration as an integrative part of our cultural history and a precious testimony to the reception and interpretation of cultural heritage throughout the generations, are emphasized in the Document of ICOMOS Germany on "European Wall Paintings and Painted Architectural Surfaces of the Middle Ages: Recommendations of how to deal with the results of earlier restorations". Published in 2002, it contains the clear statement in § 2 that the conservation of the handed-on state must always have priority -as far as it is able to agree with verifiable urgent needs of conservation (Petzet, Schädler-Saub & Exner, 2002). Without any doubt, historical restorations with their material and immaterial significance are part of monuments' authenticity. Here we can also refer to Salvador Muñoz Viñaz' "Contemporary Theory of Conservation". In chapter 4, "The decline of truth and objectivity", he criticises the concept of conservation as "truth-enforcement", i. e. the idea that conservation can reveal the true appearance of a work by eliminating later additions. Rightly he emphasises that the present condition of the work is necessarily the only actually authentic condition. Presenting the example of the de-restoration of the Lansdowne Herakles started in 1976, he points out how the removal of authentic imprints of real history (in this case, the substantial work of a neoclassical sculptor who integrated the antique marble sculpture in 1792) that were considered truth-concealing, i. e. alien to the object, is legitimated with the confusion of "authentic" with "preferred" or "expected". In this way, the subjective decisions of curators and conservators can destroy the real authenticity of a work (Muñoz Viñaz, 2005, pp. 91-99).

Piero della Francesca's Legend of the True Cross in the main chancel of San Francesco in Arezzo: the demands of historical and aesthetic authenticity
Now a central question arises: Must we generally preserve all historical restorations without any critical evaluation? Or can we preserve historical authenticity by also considering the artistic values of a monument? Referring to a central issue of Cesare Brandi's Theory of Restoration, every conservationrestoration concept needs to consider the historical instance as well as the aesthetic instance (Brandi, 1963;Brandi,1977) 6 . In this area of dialectic conflict, we must balance between two apparently opposite positions and find a wise compromise. Moreover -and this is a very complex and challenging task especially for conservator-restorers -sometimes we must consider urgent requirements of safeguarding and conservation that come into conflict with the principle of totally preserving the handed-on conditions of cultural heritage. By learning from so many radical conservation-restoration concepts also in the recent past, here we should not argue for a complete de-restoration based on false pretences of an inevitable action in order to preserve the original material, but instead advocate a wise compromise also in this technical context. 7 An exemplary case study for evaluating this complex of problems is the conservation-restoration of the wall painting cycle in the main chancel of the St. Francis Basilica in Arezzo, created by Piero della Francesca in 1453-66 and depicting in monumental scenes "The Legend of the True Cross". The conservation-restoration was carried out from 1985 to 1999 in the spirit of Brandi's theory and with the implementation of Umberto Baldini's "Methodological Unity" (Brandi, 1963;Brandi, 1977;Baldini, 1978;Baldini, 1981). 8 Without entering into the very complex analysis of their preservation conditions before the project started, it should be pointed out that the intervention was necessitated by very serious damages due to structural problems with older and newer static cracks, associated with dramatic losses of intonaco and painted surfaces, as well as by inappropriate materials applied in the past especially for the consolidation of the masonry and the wall paintings, and by widespread salt efflorescence on the surfaces with flaking and powdering phenomena on the painting layer (Un progetto per Piero della Francesca, 1989;Maetzke, 1998;Maetzke et al., 2001). The comprehensive scientific investigations at the beginning of the work led also to a deepened knowledge of the original painting techniques and 6 For Brandi, the two instances, in Italian "istanza della storicità" and "istanza estetica" are the fulcrum for developing appropriate concepts of conservation-restoration, as he explains in chap. 5 and 6 of his theory. See: chap. 5, pp. 29-37, and chap. 6, pp. 39-47, quoted from the edition of 1977 (this edition is an unmodified reprint of the edition of 1963, but with the addition of the Carta del Restauro of 1972 in the appendix). 7 In this article, these very complex technical aspects cannot be elaborated further, but we should keep clearly in mind that they can be essential for important aspects of the theory and ethics of conservation-restoration. Thus, being heedful of the demands of restoration history, e. g. a cautious cleaning of a wall painting that mediates between original parts and historical additions, can reduce the aesthetic divergence and the phenomenon of a different aging between older and younger parts and lead to the acceptance of such a historical testimony. 8 The scientific investigations and the conservation-restoration were carried out under the direction of the Soprintendenza ai beni ambientali, architettonici, artistici e storici di Arezzo and the Opificio delle Pietre Dure of Florence, with the support of the ICR in Rome, the CNR and the Institute of Chemistry and Physics of the State University in Florence. The results of the comprehensive archive research and scientific investigations are documented in: Un progetto per Piero della Francesca, 1989. of the restoration history (Un progetto per Piero della Francesca,1989;Centauro, 1989;Maetzke et al., 2001) 9 . In the context of this paper, I will analyse only some presentation aspects related to issues of authenticity, starting with notes on the restoration history of the wall paintings closely connected to these issues. The first comprehensive restoration of Piero's wall paintings was carried out in 1858-1861 by the Florentine painter and restorer Gaetano Bianchi (1819-1892), who at that time was well respected for his restorations of Giotto's wall paintings in the Bardi and Peruzzi Chapels of Santa Croce in Florence. His restoration of Piero's wall paintings in Arezzo is not traceable in all details, but archive research and findings in situ show that he reintegrated some of the big lacunae in the figurative scenes with an "impressionistic" technique by insinuating the original shades and forms in a way clearly discernible from the original painting. Such a choice at that time was innovative and unusual for Bianchi, who generally practiced an imitative reintegration of lacunae, e. g. in the aforementioned restoration of Giotto's wall paintings in Santa Croce. 10 This modern method of reintegration was probably directly influenced by the art historian and conservator Giovanni Battista Cavalcaselle (1819-1897), the great promotor of a philological method of conservation-restoration (Conti, [1973(Conti, [ ] 1988. 11 In his statements on the preservation of works of art, Cavalcaselle claimed to have full respect for the original, and even if this was in bad conditions, he asked for conservation instead of "artistic" restoration and suggested "neutral" integrations of lacunae paler than the shades of the original, thereby avoiding every sort of lie (Conti, [1973(Conti, [ ] 1988Ciatti, 2009, pp. 241-246). 12 After a comprehensive remediation of structural damages, a new restoration followed in 1915-16, carried out by the Florentine restorer Domenico Fiscali  and principally dedicated to consolidating the masonry -unfortunately with extensive cement injections. 13 But in the end, he reintegrated lacunae as well with pastel colours in order to regain a harmonic appearance of the 9 For more information on the methods and results of the investigations on the wall painting cycle of Piero della Francesca, see the following contributions: Matteini et al., Indagini diagnostiche; Bensi, Materiali e procedimenti pittorici; Lazzeri, Ricognizione visive, all published in: Un progetto per Piero della Francesca, 1989, pp. 232-284. 10 Bianchi carried out such imitative reintegration in Arezzo, too, but mainly in those parts with painted architectural elements etc. and not in the figurative scenes. See: Centauro, 1989, with a photo Fig. 107, p. 113. 11 Cavalcaselle commented on Bianchi's work on Piero's wall paintings as being conducted with "a lot of caution and love" and then he explained the "neutral" method of reintegration of lacunae: "Nuovo intonaco si fece nelle parti mancanti dandogli un colore da offender meno l' occhio del riguardante. " (Quoted from Conti [1973Conti [ ], 1988. 12 For the general principles of Cavalcaselle, see : Cavalcaselle, 1863. This document is partially quoted in: Conti [1973Conti [ ], 1988. For the above-mentioned statement of Cavalcaselle, see the following ministerial order for the preservation of paintings written by himself: Circolare ministeriale sulla riparazione dei dipinti, dettata da Giovanni Battista Cavalcaselle il 30 gennaio 1877: "Dove mancassero i colori, stendere una tinta o tinte che si avvicinino ai colori originali della pittura, tenendole sempre qualche poco al di sotto della vivacità delle tinte locali e tanto quanto non offenda l' occhio del riguardante. […] La bugia, detta ancor con bel garbo, dovrebbe essere tolta di mezzo. E con ciò lo studioso potrà distinguere in un dipinto restaurato in questa guisa quello che è originale da quello che è nuovo, a cavarne utili ammaestramenti". (Quoted from Ciatti, 2009, p. 245). 13 The consequences of these cement injections for the preservation of the wall paintings were dramatic; see: Un progetto per Piero della Francesca, 1989, andMaetzke et al., 2001. fragmentary paintings. He emphasized the advantages of this method, probably inspired by the principles of Cavalcaselle, by claiming that pastel colours are easily removable and clearly discernible from the original (Centauro, 1989, p. 132). 14 Fiscali criticised Bianchi's reintegration with "erroneous tempera colours" and removed many of them, but not all. 15 [Fig. 8] 14 This is the explanation of Fiscali: "Il mio restauro a pastello fu preferibile ad altro sistema, prima perché è di facile rimozione qualora non piacesse, poi per non confonderlo con vecchi restauri eseguiti (forse troppo in abbondanza) con sbagliati colori a guazzo. " (quoted from: Fiscali, D. (1917). Relazione sulle riparazioni ai dipinti murali di Pierro della Francesca nel coro di San Francesco in Arezzo. In: Cronaca delle Belle Arti (Supplemento al "Bollettino d' Arte", 1/2, gennaio/ febbraio 1917). This document of Fiscali is quoted from Centauro, 1989, p. 132. Findings in situ and the analysis of historical photos show that Fiscali did not use only pastel colours for his reintegration but also pencils, e. g. for drawing the contour plot. See Maetzke in: Un progetto per Piero della Francesca, 1989, pp. 69-70. 15 In doing so, some of Bianchi's "impressionistic" reintegration in the lacunae were preserved as well as some of his more imitative reintegration in the background of figurative scenes, such as the treetops in the "Esaltazione della Croce". See A new conservation-restoration of the wall paintings followed in 1961-65, carried out by the renowned conservator-restorer Leonetto Tintori . It was based on modern scientific investigation but unable to remove or at least to reduce the deterioration causes. 16 Concerning the aesthetic presentation concept, a scientific committee decided to substitute all historical reintegration of lacunae with pure and light "neutrals", with very little variations of tone but without any formal insinuation. In practice, Tintori and his team applied a thin "neutral" coating directly on the historical reintegrations of 1858-61 and 1915-16, without removing them. 17 All the professionals involved agreed with the result of these "neutrals"; only Cesare Brandi was aesthetically not convinced by the tone (Centauro, 1989, p. 139). After the conclusion of the work, the presentation of Piero della Francesca's painting cycle with the "neutral" treatment of lacunae provoked violent debates on the presentation concept. The art historian and conservation-restoration expert Alessandro Conti complained not only about these "neutrals" but also about the arrogance of those responsible for the removal of the aesthetically much better reintegration carried out by the predecessors (Conti, [1973(Conti, [ ] 1988. [see Fig. 8-9] As this case study exemplifies, the research on restoration history should also consider former debates about the quality of a coeval intervention, especially concerning its aesthetic results because in contrast to conservation treatments, they are well visible not only for experts but also for the public. Thus, we can make the case that the claim for preserving historical restorations in the name of authenticity cannot be generalised but needs critical evaluation with respect to ethical and aesthetic principles as well as to scientific and technical aspects and to the social context of its time. 16 Unfortunately, detailed reports on Tintori's conservation-restoration do not exist, but the investigations of the 1990s could identify in large part materials, methods and techniques of this intervention, see: Un progetto per Piero della Francesca, 1989. In observing the wall painting cycle of Piero della Francesca, in particular the scene with the "Victory of Constantine over Maxentius at Pons Milvius", after the restoration by Leonetto Tintori in 1961-65 ( Fig. 9), we can notice at once how the accidental but very eye-catching shapes of the lacunae distort the artistic message of the painting. Moreover, these shapes are unfortunately stressed by the so-called neutral reintegration, which in addition has darkened in the meantime. Could it be that we are looking at a curious form of a cloud in the foreground of the scene? Should it be part of a particular spatial effect wanted by the artist? We can notice a certain disorientation, an excessive demand on the observers who simply want to enjoy and to study Piero's painting. Here we can quote Brandi's accurate analysis of the lacuna in his "Postscript to the treatment of lacunae" of 1961 18 : "… a lacuna is an unjustified, even painful interruption in the form. Moreover, if we remain within the limits of the epoché (that is, if we remain within the limits of immediate perception), through the spontaneous pattern-making of perception, we will interpret the lacuna in terms of a figure and a ground. The lacuna will be sensed as a figure that relegates the painted […] image to the background, against which the lacuna 'figure' stands out. The disturbance produced by the lacuna comes much more from this receding of image to ground, and from the lacuna's violent intrusion, as a figure, into a context that tries to expel it, than from the formal interruption that the lacuna produces within the image. " (Brandi, 1977, quoted from Brandi 2005. Thus, for Brandi the goal of an appropriate aesthetic presentation is "… to reduce the lacuna's perceived prominence as a figure. […] Any ambiguity caused by the lacuna must be supressed; that is to say, its reabsorption of the image, which would thereby be weakened must be avoided. " (Brandi, 1977, quoted from Brandi, 2005. 92) Brandi in such a case was perfectly conscious of the aesthetic problems of "neutral zones", which mostly could not improve the perception of a fragmentary art work. He usually aimed to create a different spatial situation between the painting and the lacuna with the goal to push the latter in the background -and probably he regretfully noticed that this intent in Arezzo failed with Tintori's "neutral" reintegration. Instead of preserving or more precisely restoring these very poorly preserved "neutrals" of the 1960s, in the 1990s the "potential unity" of the fragmentary painting was strengthened by reducing the visual predominance of the lacunae and by supporting the original painting with clearly discernible reintegration carried out with Astrazione cromatica and Selezione cromatica, following Baldini's "Methodological Unity" with an appropriate reintegration method for the different typologies of lacunae. 19 As Baldini emphasized, that could be the way to transform a lacuna from a painful interruption to a clearly discernible proposal for a connection between the lost and the still preserved 18 This Postscript was a paper Brandi delivered to the 20 th Congress of Art History, New York, September 1961. It is published in the appendix of the Teoria del restauro, in the edition of 1977. Here it is quoted from the English translation of Brandi's theory of 2005. 19 See: Baldini, 1978, Baldini, 1981. The Astrazione cromatica offers an objective aesthetic solution for the reintegration of large lacunae that cannot be reconstructed. It reduces their formal impact and thereby, increases the legibility of the original image. The vibrant colour effect of four pure colours on a light background applied with short hatched lines, offers a logical alternative to the traditional neutral integration. The Astrazione cromatica can create an abstract structure that merges optically with the contiguous original. The Selezione cromatica is a further development of Brandi's concept of Tratteggio; its strictly vertical structure is abandoned. The lacuna is reintegrated with short parallel lines in pure colours on a light background, which follow the shapes and contours of the original alongside them. parts of the painting. [ Fig. 10] A comparison of a detail from the scene "Victory of Constantine over Maxentius at Pons Milvius" depicting Emperor Constantine, before and after the last conservation-restoration, i.e. with the former and the actual reintegration of lacunae (Fig. 11-12), emphasizes a theme of Brandi's concept of the "historical instance" with its multi-layered facets. Without any doubt, even the worst reintegration does document human activity and therefore it should not be removed. This position seems historically perfect, but in fact it leads to a conviction of non-authenticity or falsification of the entire work of art. (Brandi, 1963;Brandi, 1977, p. 37) Thus, in evaluating historical reintegration, we cannot avoid a value judgement if we want to preserve the historical authenticity of a work, in terms of a philological critique of the handed-on interventions of the past. 20 Furthermore, with reference to Brandi's "aesthetic 20 Here we must refer to Brandi's definition of conservation-restoration as a critical act of analysis and interpretation of the handed-on conditions of a work of art. Based on the Italian tradition of the philological methodology in art history and art criticism, this means performing the scholarly analysis of a work of art as a historical document, with its original material and all material traces of its history. It emphasizes the great challenge of conservator-restorers, because conservation-restoration is a highly specialized act of hands-on art criticism. See the Chapter 1, "The concept of restoration", in Brandi's Theory of Restoration (Brandi, 1963;Brandi, 1977, pp. 3-8). instance" we need also a value judgement if we want to preserve the aesthetic authenticity, sustaining a comprehensive perception and understanding of the artistic message. 21 The conservation-restoration of the 1990s respected the historical and aesthetic values of the wall painting cycle in terms of a scholarly investigation and critical evaluation of its handed-on conditions. The treatment of lacunae in the scene depicting the "Exaltation of the True Cross" shows that a value judgement can argue for the preservation of an "impressionistic" retouching carried out in the midnineteenth century by Gaetano Bianchi, because at that time, such a reintegration was a very avantgarde concept influenced by the already mentioned Giovanni Battista Cavalcaselle. This retouching was uncovered, removing the "neutral" reintegration of the 1960s, and preserved as a valuable historical testimony. [Fig.13] Thus, the critical evaluation of a series of historical restorations and their material remains does not at all mean "either preserve them or remove them"; instead, a detailed analysis and interpretation of all findings is required, step by step. In fact, in Arezzo a sophisticated concept of conservation-restoration could be realised, able to preserve this meaningful work "in the full richness of its authenticity". We can suppose that Brandi would have been very pleased with this result! 21 Brandi's terms "istanza della storicità" and "istanza estetica" are deduced from the juridical term "istanza". Thus, these "istanze" demand the respect of all requests concerning historical, artistic and aesthetic issues and, in the end, a well-balanced value judgement.

The façades of Palazzo Thiene in Vicenza: preservation and mediation of authenticity by means of reconstruction.
The third case study is focused on authenticity issues of architectural surfaces: what is the best way to preserve historical materiality and to emphasize historical appearance? In every-day practice of built heritage preservation, conservators and all other involved persons are often confronted with questions concerning the conservation and reconstruction of render, plaster, paint layers, architectural polychromy, and so on, but in the debates about the legitimacy and significance of reconstruction, these widespread problems are mostly neglected. For this reason, the façades of Palazzo Thiene in Vicenza might illustrate the challenges of preserving architectural surfaces by means of conservation and reconstruction. For a better understanding, it is helpful to start with a few notes about history. The palace was commissioned by Marcantonio Thiene in 1541 and described and illustrated by Andrea Palladio in his "Quattro Libri dell' Architettura", so there are no doubts about Palladio's authorship. Rather unclear, however, are the procedure of the construction work and the dating of the construction phases. In contrast to the original project of a monumental Palazzo with four wings around a courtyard, only the eastern wing and part of the northern wing were built. The stone cornices underneath the Piano Nobile of the eastern wing, on the side of the courtyard and on that of the street, are respectively marked with the year dates 1556 and 1558, so these dates could be related to the construction of the existing wings. (See for example : Cevese, 1952;Puppi, 1973) The first handed-down restoration of the façades dates to 1872-73, after the acquisition of Palazzo Thiene by the Banca Popolare di Vicenza. At that time, the building was in bad condition, so a comprehensive restoration was required, including among other things a new plastering and paint coating of the façades. After this intervention of 1872-73, a new restoration of the façades was carried out only in 1952. In the 1980s, those façades were in a very poor state of preservation, with a few fragments of various plaster layers. The brick masonry was visible to a large extent, clearly distinguishable from the ashlar stone masonry, despite patina and dirt. [ Fig. 14] As various Renaissance façades in Vicenza at that time presented visible brick masonry, due to a lack of maintenance and care and the consequential loss of historical plaster layers, the public had accustomed itself to this "historical" appearance. Some experts subscribed to this view of an intentionally visible brick masonry also for Palazzo Thiene, even though Andrea Palladio's plan of the east façade suggests that the contrast between brick masonry and ashlar stone masonry was not projected by the architect (Palladio, 1570). 22 [Fig. 15] 22 See e. g. Pane, 1961. The discussion of whether some of Palladio's Palazzi -not only Palazzo Thiene -originally might have presented visible brick masonry or not, was current until the 1980s, due to a lack of scholarly investigation on the plaster layers and coatings of the façades.
Through scholarly stratigraphic and scientific investigations of the masonry and the plaster layers carried out in 1988 with a team of conservator-restorers and a building archaeologist, it was possible to identify fragments of plaster and surface finish from the sixteenth to the twentieth century (Schädler-Saub, 1994a and1994b). 23 The results proved that Palladio's intent was a monochrome design of the façades, with thin layers of intonaco refinished with a layer of marmorino applied in fresco technique on the smooth surfaces in brick masonry of the Piano Nobile, i. e. the representative upper floor. [Fig. 16,17,18] The off-white surface originally corresponded to the colour of the characteristic limestone of Vicenza, used for example for the architectural framework of the windows and for the corner ashlars of Palazzo Thiene. The hammered brick ashlars of the ground floor in the sixteenth century were covered by a plaster with mineral additives of different grain size, to accentuate the rustic texture of the surface, making it nearly non-distinguishable from the stone ashlars. The original result was a persuasive illusion of a façade built completely in stone. A few pieces of information concerning the historical restorations of the façades should be noted here. The intervention of 1872-73 respected traditional materials and techniques of plastering but with a different aesthetical interpretation concerning especially the plastering of the hammered brick ashlars at the ground floor. Instead of the original soft plastering with pictorial effects, the flanks of the ashlars received a thick rectified plaster layer, with a dramatic accentuation of light and shadow contrasts. At the Piano Nobile, the relative thick new plaster layers accentuated the shadows of the thereby increased recession of the joints. Instead of a marmorino, a paint coat in yellow ochre was applied on the surface of the new plaster. All in all, the plaster layers of 1872-73 contributed substantially to the conservation of the subjacent layers of the sixteenth century. The restoration of 1954 operated mostly on the architectural surfaces of the ground floor; for the first time, a cement plaster or Roman cement plaster was applied, then a finishing with an ochre paint coating. The goal of the conservation-restoration in the 1990s was to preserve the historical plaster layers of the sixteenth and nineteenth century, 24 and to reconstruct the plaster layers of the sixteenth century as a protective and decorative coat, with the original materials and composition. On the part of the owners as well as the persons in charge, initially there was some reservation about the result of such a reconstruction, due to the loss of patina, i. e. the loss of the familiar and clearly old appearance of the Palazzo. Above all, the involved experts had to admit that a perfect reconstruction of the Renaissance design was impossible. Due to the aging of the limestone, the original monochrome appearance of the façades was not achievable. Moreover, the original aesthetic interaction between the brick masonry and the plaster layers could not be attained, due to the relatively thick packet of the subjacent historical fragments in some places, and to the technically impossible reconstruction of the fresco technique. Regardless of these limitations, thanks to a good communication with all persons involved, in the end the concept of a preservation and mediation of authenticity by means of reconstruction was accepted and could be implemented in practice. 25 [ Fig. 19] 24 The plaster of 1954 could not be preserved, mainly for reasons related to the conservation of the subjacent layers. For the evaluation of the damages and a detailed explanation of the concept of conservation-restoration, see: Schädler-Saub, 1994a, pp. 144-149, andSchädler-Saub, 1994b, pp. 246-249 and253-254. 25 Such a proceeding is also emphasised in the ICOMOS Principles for the Preservation and Conservation/Restoration of Wall Paintings, adopted in 2003. See the following passus in Article 5: "In some cases, reconstruction of decorative wall paintings or coloured architectural surfaces can be a part of a conservation-restoration program. This entails the conservation of the authentic fragments and may necessitate their complete or partial covering with protective layers. A well-documented and professionally executed reconstruction using traditional materials and techniques can bear witness to the historic appearance of facades and interiors. " (ICOMOS Principles for the Preservation…, 2003, p. 192). Now we wonder: where is the authenticity of Palazzo Thiene's façades, with all these differences? Without any doubt, we can find authenticity in the preserved material fragments as truthful sources of information, 26 as well as in the reactivation of traditional craftmanship, with proven and long-time forgotten materials and techniques of plastering, e. g. the surface refining with a marmorino. Finally, with all given restraint, the reconstruction is an approach for visualizing the aesthetic intentions of Palladio. Thus, we have meaningful elements of authenticity in these façades, even though today they look quite different from the original. We can add a postscript: the reconstruction of the architectural surfaces of Palazzo Thiene was in the course of a few years so well accepted by the public and by the experts, that various subsequent conservation-restorations of Renaissance Palazzi in Vicenza have adopted this concept, at least from an aesthetic point of view. 26 Indeed, the benefit would have been greater if the site management had scheduled from the beginning of the reconstruction work a close interdisciplinary cooperation between the conservators and craftsmen in charge, with the goal of preserving as much as possible the findings of the sixteenth and nineteenth century.
Ursula Schädler-Saub 320 Fig. 19 Vicenza, Palazzo Thiene, The façades from Contrà San Gaetano, after the conservation and reconstruction of the plaster layers of the 1990s (Photo Credits: Christoph Ulmer)

A short conclusion
The three case studies have been able to exemplify some of the multi-layered meanings of authenticity characteristic for Europe. Firstly, authentic can be the preservation of various receptions and interpretations of cultural heritage throughout time, respecting as far as possible all handed-on material layers of restoration history. Secondly, authentic can also be the critical evaluation of a series of historical restorations and their material remains concluded with a scholarly-based value judgement, with the goal of a sustainable preservation of cultural heritage in its essential material and immaterial features. Thirdly, authentic can even be a reconstruction of architectural surfaces as a method for the sustainable protection of historical findings, and a good way to visualize historical presentations and to hand on traditions of craftmanship. Since the Venice Charter (1964), the term authenticity has taken an international starring role in the theory and practice of heritage preservation, in spite of or maybe due to its "shimmering vagueness". Even if a scholarly-based mandatory definition of the term seems all but impossible, authenticity is one of the most appreciated and widespread terms in a professional and social context, well known by experts and non-experts, and thus is suitable as an umbrella term. We can use this umbrella term in interdisciplinary and transdisciplinary communication, keeping in mind that behind it we undoubtedly will find very different and contradictory values, from historical and aesthetic to social and emotional ones, and likewise different tasks. However, to avoid the use of the term authenticity as a catch-all that can mean everything or nothing, the relationship with case studies can bring awareness about the broad palette of these values and how the theory and practice of heritage preservation are always intertwined. In the end, it is imperative to include in the extensive discussion about the preservation of authenticity the specific individual profile and the materiality of each particular example of cultural heritage as it has been handed on to us. In the concluding remarks of his essay "The cult of authenticity in the age of fake", Wilfried Lipp calls for an upgrading of the substantial historic-authentic with all its intangible connotations, and in this context, he clearly defines the position of the involved experts: "Keeping in mind -once again -that all the fake, fiction and reproduction phenomena are based on the core idea of the true authentic of which preservationists and conservationists [i. e. conservatorrestorers], also in future, should keep the key competence. " (Lipp, 2010, p. 275) Let us therefore embrace this task in our roles as preservationists and conservator-restorers in order to achieve, with our specific competences, a broader interdisciplinary and transdisciplinary cooperation!