Master Thesis Conservation and Restoration of Cultural Heritage
Digital Reconstructions for Architectural Paint Research
Comparing digital visualisations for the restoration of the
Regentenkamer in the Arend Maartenshof
Specialisation: Historic Interiors Author: Julia Miriam van Velzen Student nr.: 11048522 E-mail: Julia.vanvelzen@student.uva.nl University: University of Amsterdam Thesis supervisor: M. N. (Merel) van Schrojenstein Lantman MA, PdRes Second reader: drs. F. (Femke) Prinsen Date: June 2018 Words: 16685Velzen, UvA, 2018 2 Figure cover: Author, screenshot of the three-dimensional reconstruction in Blender, June 2018
Table of contents
Table of contents ... 2 Abstract ... 4 Nederlandse samenvatting ... 5 Introduction ... 6 Research methods ... 7 1 Current scientific knowledge ... 8 1.1 Reconstructions in architectural colour research ... 8 1.2 Digital reconstructions used in restoration ... 12 1.3 Digital reconstructions used in other disciplines ... 12 1.4 Conclusion ... 13 2 Case study: Architectural paint research of the Regentenkamer in the Arend Maartenshof ... 15 2.1 Context of the case study ... 15 2.2 Stylistics of the current room ... 16 2.3 Archival information ... 20 2.4 Former restoration ... 22 2.5 Condition of the paint layer ... 23 2.6 Paint layer built up ... 23 Phase I ... 25 Phase II ... 25 Phase III ... 26 Phase IV ... 26 2.7 Layer built up of the ceiling ... 26 2.8 Comparing the wall to the ceiling ... 27 Timeframe of colours found in the room ... 28 2.9 Conclusion ... 28 3 Translating colours into digital equivalents ... 30 3.1 Colour perception ... 30 3.2 Colour evaluation for architectural paint research ... 31 3.3 Colours found in the case study ... 32 3.4 Conclusion ... 34 4 Making a digital reconstruction ... 36 4.1 Physical and digital reconstructions: a difference ... 36 4.2 Programmes for making digital reconstructions ... 37 4.3 Reconstructing the Regentenkamer ... 38 Making a digital reconstruction in Blender ... 39 Making a digital reconstruction in Photoshop ... 41 4.4 Conclusion ... 44 5 Discussion: 2D versus 3D ... 45 5.1 Advantages ... 45 5.2 Disadvantages ... 46Velzen, UvA, 2018 3 5.3 Conclusion ... 47 Conclusion ... 48 Further research ... 49 Acknowledgements ... 50 List of works cited ... 51 List of figures ... 55 Appendix I Arend Maartenshof monument sheet ... 57 Appendix II Orientation and overview of the room ... 59 Appendix III Timeline of the Regentenkamer ... 60 Appendix IV Cross-sections and Paint Stratigraphies ... 61 Cross-sections ... 61 Paint Stratigraphies ... 73 Appendix V SEM-EDX report ... 77 Appendix VI RCE report SEM-EDX Regentenkamer ... 127 Appendix VII Digital Reconstructions ... 138
Velzen, UvA, 2018 4
Abstract
The aim of this thesis was to research if digital reconstructions are useful to visualize the results of architectural paint research. The last decennia digital techniques have increased in popularity, but in the discipline of colour research drawings are still frequently used. Other scientific fields are more familiar with computer programmes, for example the field of archaeology. In this research two programmes for making digital reconstructions are tested: Photoshop and Blender: a three-dimensional modelling programme. Both reconstructions were made of the Regentenkamer in the Arend Maartenshof in Dordrecht. This hofje was built in 1625, but the interior was remodelled in 1701. The wainscoting and chimney are painted in a turquoise colour, which doesn’t match with the colour applied to parts of the ceiling. Architectural paint research was carried out to reveal the past finishing layers of the interior. The first finishing layer found on the wainscoting was a red colour, this colour was also found in a sample of the ceiling. After 1750 parts of the ceiling were overpainted in a dark green colour. The light green finishing layer of the second phase matches with this. The layers were dated by microscopy and SEM-EDX, after this the revealed colour areas were scanned with a spectrophotometer. This resulted in a digital colour code which was used for making the visualisations of the room. The reconstruction made in Photoshop only shows the modified colour on one wall of the Regentenkamer. This was done relatively fast, in addition this kind of reconstruction is easy to show to commissioners and interested parties. It gives a clear image of the possibility of repainting the interior of the Regentenkamer. A drawback of using Photoshop is the limited visibility of the relationship of the wainscoting to the ceiling. The second reconstruction was made in Blender. Specific knowledge is needed to understand this programme and for achieving a realistic result, this was not possible in the timeframe of this thesis. But this kind of model does clearly show the coherency in the elements of the room and it is possible to navigate through the model. In the conclusion of this research the two reconstructions are compared and assessed on how they visualise the Regentenkamer. Finally steps for further research are proposed.Velzen, UvA, 2018 5
Nederlandse samenvatting
In deze scriptie is onderzocht of digitale reconstructies als hulpmiddelen gebruikt kunnen worden voor het weergeven van resultaten van kleuronderzoek bij historische binnenruimten. Het gebruik van digitale technieken is de laatste decennia in opkomst, maar voor het reconstrueren van kleuronderzoek worden vaak nog tekeningen gebruikt. Op andere wetenschappelijke gebieden zijn computertechnieken wel veelvoudig toegepast, zoals in het vakgebied van archeologie. In dit onderzoek zijn twee programma’s gebruikt: Photoshop en Blender: een driedimensionaal modelleerprogramma. Twee reconstructies zijn gemaakt van de Regentenkamer in het Arend Maartenshof te Dordrecht. Hoewel het hofje in 1625 is gebouwd, is het interieur van deze kamer tot stand gekomen in 1701. De lambrisering en schouw zijn in een turquoise kleur geschilderd die niet overeenkomt met de kleuren die zijn gebruikt op het plafondstuk. Om de historische afwerkingslagen te achterhalen is kleuronderzoek uitgevoerd. Als eerste afwerkstadium werd een rode kleur aangetroffen, deze kleur was ook zichtbaar op een monster van het plafond. Na 1750 zijn delen van het plafond overgeschilderd in een donkere groene kleur. Hierbij past de tweede afwerkingslaag op de lambrisering, namelijk een lichte groene kleur. Door middel van microscopie en SEM-EDX onderzoek konden de lagen worden gedateerd, daarna werden op locatie de twee kleuren gemeten met een spectrofotometer. Hierdoor kon de kleur naar digitale waardes vertaald worden. De reconstructie gemaakt in Photoshop laat slechts een muur van de Regentenkamer zien, waarop de aangetroffen kleur is aangepast. Het kostte niet veel tijd om deze reconstructie te maken, daarnaast is het ook eenvoudig om deze te laten zien aan opdrachtgevers en andere geïnteresseerden. Deze tweedimensionale reconstructie geeft een goed beeld van het interieur zoals deze er na de restauratie uit zou kunnen zien. Een nadeel is dat de relatie van de lambrisering met het plafond beperkt zichtbaar is. De tweede reconstructie is gemaakt in Blender. Tijdens het vervaardigingsproces bleek dat specifieke vakkennis nodig is om een realistisch resultaat te behalen. Daarentegen laat dit model de relatie met het plafond goed zien en kan het model van meerdere invalshoeken bekeken worden. In de conclusie van dit onderzoek zijn de twee gemaakte reconstructies vergeleken en beoordeeld op het visualiseren van de Regentenkamer. Daarnaast zijn verdere stappen voor vervolgonderzoek voorgesteld.Velzen, UvA, 2018 6
Introduction
Nowadays technology is everywhere, from computers and smartphones to digital libraries. In scientific fields the use of computers and digital devices has become standard. In the domain of conservation and restoration, digital technologies are used more often, for damage mapping in Photoshop or documenting a room with an Ipad. In addition, advanced technologies are used to scan objects and print missing parts.1 The underlying concept is to serve in the best interest of the object and to minimalize loss. In this thesis the focus will lie on the use of digital programmes for making reconstructions for architectural paint research. The latter is a restoration practice, which is carried out frequently in historic interiors, offering an insight into the former paint layers of a building exterior or interior. By removing paint layers, one at the time, with a scalpel knife the former paint layers of an area are exposed. As a result the different finishing layers of an interior can be determined. The use of paint stratigraphies in combination with sampling can reveal the former finishing layers in a structured overview. A restorer can determine which colour was applied in a certain timeframe by comparing the paint stratigraphy to archival information of the building. Because a small area of the colour is revealed, it is difficult to imagine what the colour of the whole wainscoting may have looked like. Therefore a reconstruction is made to mark which element of the interior had which colour. These reconstructions are often drawn by hand; in this thesis the digitalisation of this process will be examined, as this has not yet been investigated. Two different reconstructions will be made and compared to determine which one is most useful for visualising the results of architectural paint research. In order to investigate this the Regentenkamer of the Arend Maartenshof will serve as a case study (see appendix I). This hofje is situated in the historical city centre of Dordrecht in Zuid-Holland. The hofje was established in 1625, and in commemoration of 400th anniversary in 2025 the Regentenkamer will be restored. Its interior, consisting of a chimney with chimneypiece, a wainscoting, a large ceiling painting and a row of portraits along the walls of the chamber, was redecorated in 1701. One objective of this restoration project is to find out what the historical finishing layers of the wainscoting and chimney are. Two reconstructions will be made to show what the restoration of the room can look like, based on the colours found in the interior. This leads to the research question: are digital reconstructions usable for visualising the results of architectural paint research? The first chapter will explain the status quo of the use of digital technologies in cultural heritage fields. The second chapter is dedicated to the case study of the Regentenkamer and the architectural paint research; the original finishing layer of the interior will be identified. The following chapter analyses how a visible colour can be translated into a colour code that can be used for computer manipulation. The colours found during the architectural paint research will be identified using a spectrophotometer. This information is used for making the two digital reconstructions in the fourth chapter. In the last chapter the two models will be compared and their value for architectural reconstructions will be determined. 1 Beentjes, van der Molen 2013Velzen, UvA, 2018 7 Research methods This research was divided into two parts. First the focus was on the Regentenkamer of the Arend Maartenshof. For this case study archival research needed to be carried out, to get insight into the history of the building and the use of the room. The architectural colour research consisted of making paint stratigraphies and sampling the paint layer. This was documented and further analysed with microscopy and the analytical technique SEM-EDX. Combined, this research gave insights into the finishing layers of the interior and at what time they were present. The second part of the research focused on the digital reconstructions; with a spectrophotometer the colours were translated into a digital colour code. The two reconstructions were created in the digital programmes Photoshop and Blender. The advantages and disadvantages of both are discussed, to form a supported argument for selecting the most favourable method.
Velzen, UvA, 2018 8
1 Current scientific knowledge
This chapter will focus on the current scientific knowledge in different academic fields which is relevant to digital reconstructions used for the restoration of cultural heritage. The thesis will discuss the subject of digital reconstructions and architectural paint research; this angle will be used to establish the current thoughts on this side of the field. Major themes, topics and trends will be addressed and evaluated. The first paragraph describes how reconstructions are used in colour research. The second paragraph discusses different digital reconstructions used in restoration. The third paragraph focuses on how digital reconstructions are used in other cultural disciplines. Primarily the discipline of archaeology will be the source for information. Different case studies will be examined and compared with historical interiors. In the conclusion the different paragraphs will be compared and it will discussed how the research question fits in this framework. The aim of this chapter is to get an understanding of the different levels and developments in architectural paint research and in the making of three-dimensional reconstructions for different purposes. 1.1 Reconstructions in architectural colour research Different things can be indicated by the notion of reconstruction in architectural colour research. First of all the word reconstruction can refer to the reconstruction of the paint layer, so applying the new paint and thereby reconstructing a former paint layer. But it can also be used as a tool in the process of architectural paint research to help to identify where the paint was applied. A model can be made by the researcher to indicate what colour was applied on an architectural element, and what the result may have looked like. The aim of architectural paint research is to unravel the historic finishing layers of a fixed architectural or interior element. A paint stratigraphy gives insight into colours once applied on an object, usually a small section of the former layer is revealed. For a decorative layer it is possible to expose this layer by removing the later overpaintings by hand. However, for an monochromatic colour, it would be too expensive and time consuming to reveal this by hand, so applying a new paint layer is often the reality in architectural paint research. A reconstruction, as a model, can help decide where which colour was applied according to the paint stratigraphies, building history and other archival information. If more subsequent finishing layers are present, more models can be made to visualise the difference and evolution of the room over time. An example is the ladies’ boudoir from the Willet Holthuysen in Amsterdam. Two reconstructions of the room were drawn when colour research was carried out (see fig. 1.1).2 The two drawings were executed and coloured by hand. Pencils and watercolours were often used for indicating the colours used. 2 Allersma et al. 2016: 43Velzen, UvA, 2018 9 Figure 1.1, two reconstructions of finishing layers in the Willet Holthuysen Drawings are frequently used in other architectural paint research reports. They can give a quick impression of a former situation. However, since a few decades digital media have grown and so have computer programmes to draw and model interiors. Those digital tools are slowly beginning to be applied in architectural paint research and reconstructions. For example, in an article about a former finishing layer of a room in the Martenahuis in Franeker, a digital manipulation of a photograph was used to give an impression of the former decoration of the room (see fig. 1.2).3 3 Verslype et al. 2017: 108
Velzen, UvA, 2018 10 Figure 1.2, digital impression of the brown tromp-l'oeil decoration, altered photograph, L. de Moor This is just one instance of the application of digital techniques. Another example is part of the study group Dordtse Kleuren, that focuses on exterior colours in the city of Dordrecht. For more than fifteen years this study group has carried out architectural paint research. In one of their publications they use digital drawings to compare two different colour schemes on the façade of four buildings (see fig. 1.3).4 Various architectural elements show different colours. Figure 1.3, two digital drawings showing different colour schemes on four buildings The digital file of the outlines of the buildings was used again. This is an obvious advantage of this technique, because it can display different options. It is also possible to model a room in a three-dimensional modelling programme and alter it according to ones wishes. In doing this it is very important to interpret every colour area correctly, 4 Groeneweg, Rouw 2010: 58-59
Velzen, UvA, 2018 11 especially colours that cover a large area of the interior, because those will influence the whole atmosphere of the room.5 Another recent example of the use of a digital reconstruction in architectural paint research is the Gouden Zaal in the Mauritshuis, The Hague. This room was examined for the project: From Isolation to Coherence: an Integrated Technical, Visual and Historical Study of 17th and 18th Century Dutch Painting Ensemble. The material aspects, former restorations, historical context and more were examined in various Dutch interior ensembles with painted decorations. The Gouden Zaal was one of the analysed interiors, because of the restoration of the Mauritshuis in 2009-2014. The room has a painted ceiling and tromp-l’oeil paintings incorporated into the wall panelling painted by Giovanni Pellegrini in 1718. A part of the research focused on architectural paint research of the walls and ceiling. Whereas the walls are nowadays painted with an oak imitation, they used to have a light grey stone imitation. This imitation matched with the tromp-l’oeil paintings.6 The architectural paint research led to insight in the paint layers of the period of Pellegrini. Articles were published and a digital reconstruction for the Mauritshuis museum was made. On the website of the Mauritshuis this reconstruction can be explored (see fig. 1.4). Figure 1.4, two stills from the digital reconstruction. Left: eighteenth century. Right: today This online accessible reconstruction can be opened in full screen modus and it is possible to navigate through the room by clicking and dragging the image. The reconstruction shows the eighteenth century appearance of the room with the grey walls, gilded ceiling ornaments, original flooring and chandeliers. Even the paintings are digitally retouched, as if it was just painted by Pellegrini. The present finishing layer of the room is shown by clicking heden (nowadays). Switching between those two finishing layers it is easy to spot differences and to get a good understanding of the eighteenth century appearance. Moreover, when pressing the small plusses that appear throughout the room, extra information can be found. Written information and photographs show how the research was done. This is a good example of an interactive digital reconstruction for architectural paint research, where different finishing layers can be compared. A public with no knowledge about paint research can easily navigate through this reconstruction and access additional information about the project when interested. 5 Björdell, Rittsél 2015: 129 6 Eikema Hommes et al. 2014: 157
Velzen, UvA, 2018 12 In conclusion, drawings and other physical representations are used often in the practice of architectural paint research. The goal of a physical model might be comparable to a digital reconstruction but the creation process of the models is different. After the reconstruction of an object the result will be another object, whereas a digital three-dimensional model is a visualisation of the object, created by a different technical process.7 1.2 Digital reconstructions used in restoration In the previous paragraph the use of reconstructions in architectural paint research was discussed. This paragraph will focus on how reconstructions are used in restoration projects. Examples of techniques that are used are given in the article: ‘3D Reconstruction Methods for Digital Preservation of Cultural Heritage: A Survey’. Digital models of objects can have different purposes, for example the safekeeping of information in the event of an accident or natural disaster, to increase availability for an audience, to use as a replica or to identify art forgery. By using laser-scanning objects can be converted to digital data. This article explains what the steps are in making a model and what kind of devices or programmes are needed. As technologies rapidly replace each other, recent inventions are discussed, such as how precise is an object scanner, what are the costs, how long does it take to process, is it portable? All those points are important issues relating to scanning devices. Examples of machines and projects are given. Since in this article objects are scanned rather than created by hand in digital software, machines also do the identification of the colour. External camera input can give information about the colour of the object.8 It is not known if this is a trustworthy method, because it is not fully described in the article how this is done. The recent article ‘Application of Digital Technologies in the Restoration of Historic Buildings and Heritage Objects’ explains how three-dimensional techniques can help in the restoration process of historic houses. The use of scanning equipment makes it possible to reproduce architectural ornaments. In digital programmes it is simple to alter the ornament, rotating it or mirroring it, so that it will fit the missing part of an ornament seamlessly and no original material has to be removed. An example of a church in Belgium is mentioned where stonework was replaced. Attention is paid to the absence of craftsmanship, because the machine will replace a large part of the traditional stone carving process. Moreover, 3D printing techniques are costly and the materials used for printing are polymers, so a casting process is needed to create objects out of other materials. This article does see a future of 3D printing techniques for restoration practices.9 1.3 Digital reconstructions used in other disciplines Three-dimensional digital reconstructions are frequently used in other disciplines. Especially the discipline of archaeology has a rich history of using modelling programmes for reconstructing the past. A book which describes the use of digital modelling in archaeology is: Digital Archetypes: Adaptations of Early Temple Architecture in South and Southeast Asia written by David Beynon and Sambit Datta. The first chapter of the book explains how digital 7 Münster et al. 2016: 10 8 Gomes et al. 2014: 3-4, 10-11 9 Vanhellemont et al. 2016: 141-150
Velzen, UvA, 2018 13 models can contribute to research of architecture of temples. Archaeological temples are often not complete; throughout centuries parts may have been demolished. With the aid of computer data it is possible to reconstruct missing pieces of temples, by using calculations and proposing different options for the missing part. Digital tools can help to make objects less static and make them interactive in the form of a model that can be altered, although the degree of accuracy has to be considered each time.10 In this book three-dimensional reconstructions are used to offer different scenarios of architectural styles. Another recent and useful book is 3D challenges in Cultural Heritage II, in which different articles about cultural heritage and three-dimensional modelling are discussed. In the first article, the modelling is explained specifically for the humanities department. Digital three-dimensional reconstruction is a research method to create virtual representations of historic objects. Therefore it is sometimes called the Digital Humanities. In this field different disciplines are combined with humanities, for example architectural design, engineering and computer sciences. ‘Models are used for documentation purposes and/or testing the plausibility of historical reconstruction, as well as out of the mere interest of reconstructing lost structures. Making the phases in the construction history, that have not survived, visible again seems to be a way of retrieving them from cultural oblivion.’11 The writer deplores the lack of visual humanities research and makes a case for an increased effort towards the development of standards in this field. Both intangible heritage and tangible heritage objects can be converted into a digital model; the original, which still exists, can be simplified and modified for other uses. For example, the author can decide what the most important aspects are that he or she wants to include; insignificant things can be left out. It differs from archaeological models, considering archaeological objects are not used anymore, whereas heritage objects still remain present. Moreover, a model can include several properties, and digital reconstruction is a non-invasive technique to the object. This makes it eminently suitable for testing alterations or restoration practices. For this kind of research there are many different programmes available, for example for adding extra information, for virtual reality functions, for taking size measurements and many more. The programme must be chosen in accordance with the purpose of the reconstruction. Of course characteristics relating to the amount of detail, sharing availability or the intention to make it public, have to be taken into account. The author has to know the boundaries of the programme when making the reconstruction. This article also offers a workflow chart for constructing a visual model and the steps that need to be taken.12 1.4 Conclusion This chapter expresses the interdisciplinary character of the research. Architectural paint research of historic interiors has a tradition of making physical models for the decision-making process for restoration practices. In the past decennia the use of digital 10 Beynon, Datta 2014: 23-28 11 Münster et al. 2016: 8 12 Münster et al. 2016: 7-9, 14-15
Velzen, UvA, 2018 14 reconstructions has been expanding. Nevertheless, the making of three-dimensional reconstructions for this use has hardly been explored. This forms a sharp contrast with the domain of archaeology, where objects and archaeological architecture are recreated in digital programmes, which gives the possibility to evaluate lost structures. Applying these techniques to the field of cultural heritage is relatively new. As mentioned before, there is no set workflow established yet, although it has been tried in a few articles. There are many ways of using digital reconstructions for cultural objects. Not only as safekeeping in case of natural disasters, but also for three-dimensional printing of missing parts. The designer of the virtual model can decide what should be included or excluded. There are different ways to use digital reconstructions and the conclusion of the articles and books is, that it is evaluated as a positive development for the cultural disciplines of the humanities.
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2 Case study: Architectural paint research of the Regentenkamer
in the Arend Maartenshof
This chapter explains the case study for the architectural paint research; first the archival information, stylistics and restoration of the case study are discussed. This provides an overview of the characteristics of the room and gives useful knowledge for the architectural paint research. The second part of this chapter focuses on the architectural paint research carried out in the Regentenkamer. The outcome of this information will form the basis of the digital reconstructions. 2.1 Context of the case study The case study that is chosen for this subject is the Regentenkamer of the Arend Maartenshof, situated in Dordrecht, the Netherlands. The city of Dordrecht has a rich history and had a high status in Holland. In the heart of the old city centre the Arend Maartenshof is located. This hofje was established in 1625 by Arend Maartenszoon.13 Arend Maartenszoon, who was a wealthy investor, was born in 1555 in Dordrecht and died in 1629, a few years after financing the hofje. He had different financial functions in the city council, invested in the Dutch East India Trading Company and lent money to people. Because he charged high interest for his loans some people weren’t fond of Maartenszoon. It is said that he wanted to improve his reputation by establishing a hofje, but this is a speculation. In 1625 the hofje was built. It was intended as housing for the less fortunate women, who received a small sum of money every week.14 Nowadays the hofje still serves as residence for people with lower income, but the houses have been modified to modern standards. In 1701 the Regentenkamer was refurbished with a new interior.15 The reason for researching the Regentenkamer is the 400th anniversary of the hofje and the state of degradation of the different interior elements. The room is property of the Dordrechts Museum and a plan is made to celebrate the 400th year of existence by the restoration of the room. The restoration has been planned to be finished in 2025 and will include the treatment of the ceiling painting and the portraits hanging in the room (see fig. 2.1). 13 A hofje is a square courtyard where widowed women or the poor could live. Many Dutch cities had hofjes, mostly financed by philanthropists. 14 Molhuysen, Blok 1918: 943-944 15 This date is based on the archival record mentioned in the report of Jos Deuss, but the archival records of 1701 and 1702 do not mention this.Velzen, UvA, 2018 16 Figure 2.1, northwest side of the interior, with eight portraits 2.2 Stylistics of the current room The hofje was established in 1625 on the Museumstraat in Dordrecht. Thirty-six small houses were built on this plot, with a large courtyard in the middle. The centre of the courtyard has a water pump with a neo-gothic wrought iron frame. The entrance of the hofje has a sandstone gate designed in Renaissance style, with the year 1625 inscribed. The houses are built in greyish brown brickwork and have doors with cast iron door grids, each house has three windows. On entering the hofje, the visitor has the Regentenkamer directly on the right hand. It has a door with cast iron grid and a transom window to let more light into the room. On the southeast side of the room there are two sash windows with one horizontal and four vertical bars (see appendix II). On the inside daylight can be prevented from entering by means of shutters. The whole room is slightly tilted because of a small canal that used to be situated on the northwest side of the hofje. The interior of the hofje has a simple wooden panelling consisting of a wainscoting with raised panel, dado rail and profile trimmings. This is painted in a turquoise colour, with some small trimmings in gold. The walls are decorated with fourteen portrait pictures in wooden frames (see fig. 2.1). Two panel portraits near the chimney were painted in the year 1627, whereas others were added later, presumably after 1701 (on canvas). The room is divided into two by a wooden fence: on one side the floor has marble tiles, and the other side has floorboards painted in red. The fence marked the area where the regenten discussed issues, the tenants were supposed to stand behind this fence. The chimney is a feature that draws attention in the room. The floor plate and the back of the chimney are made of marble. The mantelpiece rests on two schorende wangen, a slanted base construction (see fig. 2.2). This type of chimney was in fashion in the Netherlands from 1680 onwards.16 Examples of a similar chimneys can be found in the dollhouse of Petronella Oortman, made in 1686-1690, and in a house on the Groenmarkt 3 in Dordrecht from 1709. 16 Fock 2001: 95
Velzen, UvA, 2018 17 Figure 2.2, chimney on the south west side of the room Hendrik Noteman did the woodcarving of the chimney, which consists of acanthus leaves in the lower parts. The mantelpiece has two coats of arms and next to the painting different kinds of carved fruits. One coat of arm displays an orb and cross, the other one is the personal coat of arm of Arend Maartenszoon. The allegorical scene displays a woman giving a golden piece of jewellery to an older woman. The painting by Arnold Houbraken (1660-1719), whose signature is present at the lower left corner, can be interpreted as visualising the virtue of charity. Before 1701 the ceiling of the Regentenkamer was also painted, and decorated with ornaments and frames. It is said that those were removed during the 1984 restoration, and only nine large beams were left behind the ceiling.17 In the last quarter of the seventeenth century it was in fashion to hide beams by installing a ceiling consisting of planks that were lined up evenly.18 Because of the smooth surface with no beams present, a decorative scene could be painted on the ceiling, as was done in the Regentenkamer (see fig. 2.3). 17 Deuss 1984: 2 18 Fock 2001: 168
Velzen, UvA, 2018 18 Figure 2.3, the ceiling of the Regentenkamer The middle part of the ceiling depicts the scene of Mars, the god of war, in conflict with the personification of time. To the left of Mars there are three putti holding the coat of arms of Arend Maartenszoon. This scene is framed with a green border with in the middle a golden bow of leaves crossed with ribbons. The rest of the ceiling is divided into nine compartments with acanthus leaf decoration, against a grey marbled background. The piece is executed in oil paint. The painter mentioned in the archive is Arnold Houbraken, though this painting is of lesser quality than the chimneypiece. Therefore it is assumed that students of Houbraken had a hand in this.19 Towards the end of the seventeenth century another way of decorating a ceiling was to have a canvas painting installed on the ceiling, surrounded by wooden frames.20 An example of this is the painted canvas on the ceiling in the estate Trompenburg, in ‘s-Graveland (see fig. 2.4). This ceiling shows an allegorical scene painted on canvas in a wooden frame painted in 1684. The frame is further divided by smaller paintings on canvas, in a tromp-l’oeil style. This ceiling was researched for the project From Isolation to Coherence, executed from 2012 till 2017. This project examined Dutch interiors with canvas paintings that were designed as a whole. The aim of the project was to emphasize the importance of ensembles for Dutch interior history and to raise awareness for their safekeeping.21 19 Deuss 1984: 1 20 Fock 2001: 168 21 < http://www.fromisolationtocoherence.nl/casussen/trompenburg.html > 7th of June 2018
Velzen, UvA, 2018 19 Figure 2.4, ceiling piece by Johannes Voorhout, 1684 When the Trompenburg ceiling is compared with the ceiling of the Regentenkamer, it can be observed that there is also a division in the Regentenkamer ceiling painting. The latter is painted on wood, but architectural frames are indicated by means of the green borders (see fig. 2.3). This indicates that the ceiling of the Regentenkamer has tromp-l’oeil elements, with the painting making the suggestion of an open ceiling and giving a glimpse of the sky. Therefore the wall panelling and ceiling were designed as a coherent feature of the room. Another example of a tromp-l’oeil ceiling is the painted ceiling of the Oenemastate in Heerenveen. This was painted in 1663, so painted four decennia earlier than the Regentenkamer ceiling. The painting shows a division of the ceiling into wooden beams, which are painted on the flat wooden ceiling. In the centre the painter created an opening to the sky. This shows that there was a tendency of imitating architectural structures in ceiling paintings.22 A handbook on how to create realistic ceiling pieces was written by Gerard de Lairesse in 1712. A section of the book is dedicated to this subject, therefore showing the popularity of tromp-l’oeil ceilings.23 Furthermore, in the corner across the door, a large trunk is standing with a painted decoration. The decoration depicts a coat of arms with an eagle on top and branches curling around it, together with a banner against a grey background. The text on the banner says: ‘chest wherein lie papers and documents about the hofje founded by the late Lord Arent Maertens van Barendregt in his lifetime Lord of Eastern Barendregt Schobbelantsambact.’24 According to this text the chest contained records concerning the hofje. In the middle of the interior there is a large wooden table with turned table legs, surrounded by six chairs. The chairs have a wooden frame and leather furnishing, which has started to dry out and is coming off the chairs, showing the filling material. 22 < http://www.fromisolationtocoherence.nl/english/thema/piet.html > 7th June 2018 23 Lairesse 1712: 137-159 24 ‘Kiste te waer inn leggen papieren en documenten specierende tot den hof gestigt by wyle den heer Arent Maertens van Barendregt in syn leven Heer van Oost Barendregt Schobbelantsambact.’ Translation: Julia van Velzen
Velzen, UvA, 2018 20 2.3 Archival information Of almost every year from 1648 until 1940 a record is kept by the Regenten, the trustees of the hofje. In those records it is mentioned who passed away or what kind of maintenance was carried out in the hofje. In the record of 1701 the renovation of the hofje was not registered. Likewise there is no information about who installed the new interior. There are a few photographs in the image database of the archive of Dordrecht that show the Regentenkamer in former times. The oldest photograph was made between 1958 and 1962, and shows the west side of the interior (see fig. 2.5). Figure 2.5, the Regentenkamer around 1960 From this black and white photograph it is impossible to tell which colour the room has. However, it can be noticed that the coats of arms of the chimney are painted in another colour like some of the trimmings and the raised panel of the wainscoting which have a different colour compared with the rest of the wall. Furthermore, there is a small cupboard construction in front of the chimney. The table is covered by a tablecloth of which the volunteer of the Regentenkamer said that he found this cloth in the large archive chest; the fabric was deteriorated so it was discarded.25 Two slides of the collection of W. van den Berg show the Regentenkamer in colour (see fig. 2.6, 2.7). The collection of W. van den Berg contains many drawings and slides of monuments and restoration projects. The slides are not dated, but in the collection the restoration of the city hall of Dordrecht has been documented. This was in 1975, thus it can be concluded that the slides are from this period. 25 Koningh, C.J., conversation held on the 19th of December, 2018
Velzen, UvA, 2018 21 Figure 2.6, the Regentenkamer in the greyish brown colour scheme Figure 2.7, the Regentenkamer in the greyish brown colour scheme The two slides show the Regentenkamer in a greyish brown colour. Again there is a difference between the raised panels of the wainscot, the chimney ornaments and profile trimmings. It can also be noticed that the condition of the surface paint is not that good: paint loss is visible (see fig. 2.7). The room nowadays has red floorboards, but in this picture they appear to be grey.
Velzen, UvA, 2018 22 Another photograph shows the room in 1982, a few years before the restoration by Jos Deuss (see fig. 2.8). From this black and white photograph it is hard to judge the colours of the wall. On examining the photograph it became clear that the paint is damaged in the same areas as shown on the slides of 1975. Therefore it can be confirmed that the greyish brown colour was still present in 1982. Figure 2.8, the Regentenkamer in 1982 The portraits, the table and chairs have been all removed from the Regentenkamer in 1982: presumably because of the restoration that took place in 1984. Remarkably, a tapestry is lying on the floor, this isn’t seen in the earlier photographs. Another aspect that can be seen is the appearance of gilded profiles. The mouldings of the panel seem to reflect the light differently than the painted areas. Which is noticed in the chimney profiles and carved ornamentation of the chimney, therefore those parts might have been gilded. 2.4 Former restoration In the archive of Dordrecht there is a small booklet from 1978 called The Restoration of the Arend Maartenshof in Dordrecht. In this year and the following years the hofje was modernized to the standards of that time, because the construction of the houses was deteriorated and proved to be unsafe for living. The municipality of Dordrecht funded the project, which was estimated to cost around four and a half million guilders. The Regentenkamer is not mentioned in this booklet.26 There is not much archival information about the previous restorations of the Regentenkamer. The only document that is available is of the restoration of the ceiling painting in 1984. This restoration was carried out by Jos Deuss, started in the last months 26 Regionaal Archief Dordrecht, inv.nr: 362
Velzen, UvA, 2018 23 of 1983 and was finished in 1984. The report states that before the restoration of the ceiling was started, the interior was restored. Some wooden parts of the ceiling were renewed, because they were damaged by mould growth. No overpainting of the interior elements is mentioned. It is possible, based on the photographs, that this has been carried out at some point in this decade (see appendix III). The ceiling painting was cleaned, infills were removed, lacunae were filled and old retouches were removed. Subsequently, a retouch varnish was applied, and retouches in oil paint were added to the piece. Deuss explains that after one year a final varnish must be applied, but it is not known if this was actually executed. 2.5 Condition of the paint layer The latest paint layer was presumably applied during the restoration in 1984. The colour of the current layers is turquoise; the blue or green tone perceived depends on the light coming in. Some profiles of the wainscoting and of the chimney and ceiling profiles are accentuated with a painted golden trim. After removing the paint for the paint stratigraphy it was noticed that the paint sticks to the surface very well, and parts removed stayed fixed on the paint surface. The paint can be described as smooth, elastic and opaque. When examining the current paint layer on location it was observed that the paint is in fair condition. There are no large areas with damage or severe cracking. Further examination showed that there are some parts where the wooden construction of the wainscoting caused cracks in the paint layer. It was noticed that there are areas where moisture is trapped behind the paint, with cupping and paint loss as a result. Those areas are present on the wall across the windows, and in areas near the windows, the damage is parallel to the grain of the wood. There are some spaces of paint loss caused by use of the room, for example near the hook and eye latch of the shutters. 2.6 Paint layer built up The architectural paint research carried out in the first half of 2018 consisted of different sections. At the start, a preliminary examination of the paint layers on the wall to the right of the chimney and some parts of the chimney was carried out, no other parts were investigated. With a scalpel a small spot of the paint layers was removed, subsequently a photo was made with a hand-held microscope (Dino-Lite AM4113T). This revealed where spots with many paint layers were located on the wall. A few interesting spots were selected to be examined with colour stratifications. After examining the Dino-Lite photos it became clear that the lower parts of the wall do not contain many layers. Presumably, the lower parts were replaced or sanded down at some point, thus having less coats of paint. However, the upper part of the wall showed more layers. Samples were taken of the wall panelling and chimney for examination with microscopy and SEM-EDX. Sample AMS08 serves as example for explaining the paint layers, because it shows all the paint layers of the wall (see fig. 2.9, table 2.1). There are minor differences with other samples found near this area (see appendix IV).
Velzen, UvA, 2018 24
Figure 2.9, sample AMS08, 20x enlarged
Table 2.1 layers of sample AMS08
Phase Layer Colour Main SEM-EDX elements
IV 19 Turquoise Titanium
IV 18 Green Iron
IV 17 Blue Titanium
III 16 Brown grey Zinc
III 15 Grey Zinc
III 14 Beige Lead
III 13 Grey brown
III 12 Grey Zinc
III 11 Milky White Lead
Overpaint 10 Green Lead
Overpaint 9 Green Lead
II 8 Light green Lead
II 7 Green piece Lead
II 6 Grey Lead
Overpaint 5 Light red Lead, iron
Overpaint 4 Light red Lead, iron
I 3 Red Lead, iron, calcium
I 2 Brown Binding material
I 1 Beige Calcium
Velzen, UvA, 2018 25 Phase I In most samples, directly above the wood, a beige layer is present (see fig. 2.9, numbered with 1). SEM-EDX analysis measured a high concentration of calcium in it that suggests calcium carbonate (chalk) (see appendix V AMS05(7)_pt1). This is characteristic for a preparative coat, since it is the first layer following the wood.27 Some samples have a thin brown line on top of the calcium layer; this is a separation layer containing the binding material of the beige layer. Over time it has migrated towards the surface. In some samples another brown layer contains lead with chalk and umber particles to make it brown. On top of the brown layer there are red paints present. Most of the samples have two red layers, but some samples contain three red layers. The latter applies to sample AMS08, taken from the highest profile near the ceiling. The second and third red layers of sample AMS08 show the same characteristics in the SEM-EDX analysis; both contain lead and iron (see appendix V AMS05(1)_pt4, AMS05(1)_pt5). The presence of iron points towards red ochre which has been used since antiquity.28 There are large white particles present in those layers. The first red layer contains calcium, suggesting the use of chalk, possibly from the preparative layer (see appendix V AMS08(3)_pt4). Phase II Above the cluster of red coats there is a grey layer, containing lead white. Because of the light colour and the position on top of the red layer it seems likely that this is a preparative layer for the green applied next. In most samples three layers of light green are visible, but in sample AMS06, taken on the left side of the portrait painting, there are four consecutive light green coats. The amount of green layers can indicate the times the wainscoting was repainted in this colour. Elements in the first green layer are lead, with particles containing aluminium and iron (see appendix V AMS06(2)_pt1, AMS06(2)_pt2). The presence of iron suggests Prussian blue.29 This was tested by putting a drop of sodium hydroxide on the sample AMS09. This resulted in discoloration of the green layers, indicating Prussian blue was used. In other samples large yellow particles are visible; SEM-EDX showed that those consisted of lead and antimony, so it can be concluded that those are Naples yellow particles (see appendix V AMS05(1)_pt1).30 In the second light green layer there is lead present with small blue and yellow particles, the same applies to the third layer. Naples Yellow is a synthetic inorganic pigment that was first used around 1740. During the eighteenth century there was no acceptable green pigment available, and for getting a bluish green colour two pigments had to be mixed together. Those pigments are Prussian blue and Naples yellow, in the second half of the seventeenth century this mixture was often seen in Dutch interiors.31 It can be concluded that those two pigments were used in the Regentenkamer. 27 Eastaugh et al. 2008: 98 28 Keijzer, Keune 2005: 87 29 Eastaugh et al. 2008: 315 30 Feller 1986: 219 31 Keijzer, Keune 2005: 83-84, 87
Velzen, UvA, 2018 26 Phase III Sample AMS08 is used as representative for discussing the greyish brown phase. Number 11 shows a milky white layer with transparent particles, containing lead. Layer 12 is thicker and has a grey colour, with small particles of different colours in it. In ultraviolet light it shows the distinctive starry pattern, suggesting that zinc white has been used in this paint.32 The SEM-EDX analysis confirmed the presence of zinc white (see appendix V AMS04(2)_pt1). Layer 13 is a thin greyish brown layer; this layer is not seen in many other samples. In others this is a separation layer from the grey layer underneath, but in sample AMS08 it seems to be a paint layer, because of the thickness. The beige-coloured layer 14 contains lead (white) with small bit of ochre in it (see appendix V AMS04(2)_pt2). Layer 15, is greyish brown, and comparable in colour to layer 13. This layer contains zinc, as is also seen on cross-section under ultraviolet light (see appendix V AMS04(2)_pt3). The most recent layer of the greyish brown layers is layer 16. In this a lot of binding medium has been used and a little bit of ochre and zinc (see appendix V AMS04(3)_pt1). It is concluded that this is a finishing layer. This must be the one visible in the slides of the 1970s. Phase IV The SEM-EDX analysis revealed that layer 17 contains titanium (see appendix V AMS03(2)_pt6). The pigment titanium dioxide, also called titanium white, was used in Dutch house paints from 1950 onwards.33 Moreover a lot of calcium has been used in this, suggesting an opaque preparatory layer for the finishing layers. Layer 18 is a thin green layer, containing iron (see appendix V AMS03(2)_pt7). This colour differs from the current turquoise colour that is used on the wall, but it does look similar to the green colour used on the ceiling. There is no archival information present or photographs that show that this was used as a finishing layer. However, from the SEM-EDX analysis it can be concluded that titanium dioxide is present in the seventeenth layer, so this was applied after the 1950s. In addition, the photograph taken around 1975 shows the Regentenkamer still being greyish brown, so this colour must have been applied later than 1975. At last, layer number 19 is the current layer, containing titanium dioxide and traces of ochre (see appendix V AMS01(2)_pt7). Other samples show layers of white in between the contemporary layers that contain zinc, calcium, barium and sulphur (see appendix V AMS01(2)_pt6). This suggests the presence of gypsum and barium sulphate, so this must be a preparatory layer for the current paint layer. The bronze painted profiles were also analysed, revealing copper and zinc containing paints, so no gilding was present on the profiles. 2.7 Layer built up of the ceiling The microscope analysis of the sample from the ceiling shows four layers (fig. 2.10). It was taken from the green borders mentioned in paragraph 2.3. During the research on location a faint red colour was observed behind the green, indicating that the green might be an overpaint layer. The first two layers next to the wood contain calcium and lead, suggesting chalk and lead white, and it can be concluded that those are preparative layers. On top of this 32 Fitzhugh 1997: 300 33 Keijzer, Keune 2005: 87
Velzen, UvA, 2018 27 ground a red layer is visible, containing lead, calcium, aluminium and iron, the latter is possibly related to red ochre (see appendix V AMS11(1)_pt3). A large particle in this layer contains barium and sulphur, so suggesting barium sulphate, a well-known paint extender (see appendix V AMS11(1)_pt5). Barium sulphate as a natural mineral was known in the sixteenth and seventeenth centuries. In the late eighteenth century it was discovered that, as a pigment, it could be used to make a white paint. This isn’t detected in the sample of the ceiling, because the colour of the layer is red. Barium sulphate is a low cost product, and has been used as an extender in water-based paints, but also in the preparation of lakes.34 Therefore it could not have been used in this paint layer as an extender for the lead white and red ochre. As seen on location the overpainted layer is a green layer. It contains iron, suggesting yellow ochre and Prussian blue. This green layer is now the finishing layer of the ceiling. It can be concluded that at some time during the existence of the hofje the ceiling was overpainted with green, and that the original finishing layer used to be red. Figure 2.10, cross-section of the ceiling In sample AMS08 there is a small layer of green present, above the grey layer (see fig. 2.9, number 7). This small layer is comparable to the green that has been applied to the ceiling; SEM-EDX showed that this fragment contains lead, yellow ochre and iron (see appendix V AMS08(4)_pt2). This is also found in the green layer of the ceiling. Sample AMS08 was taken from one of the profiles near the ceiling, so when the ceiling was overpainted it could have happened that some paint was spilled on the profiles of the wall, before those were painted in a new colour. It seems logical to paint the ceiling first and then paint the walls, to prevent paint splatters on a freshly painted wall. If this is the case it can be concluded that the walls were painted in a light green colour during the time the red was overpainted with green. 2.8 Comparing the wall to the ceiling As discussed in the previous paragraph, the first finishing layer had a reddish colour, containing lead and iron. In the other red layers that follow the first layer also lead and iron were found, suggesting the pigments lead white and red ochre. The red used for painting the ceiling also contains high concentrations of lead and iron, similar to that used in the paint of the wall. Moreover, traces of calcium and aluminium were found. There is one large particle in this layer that is not found in the layers of the wall, namely barium sulphate. Therefore the red used on the wall is possibly not entirely of the same 34 Feller 1986: 49, 54
Velzen, UvA, 2018 28 composition as that found on the ceiling (see appendix VI). Nevertheless, for some time period both reds have been visible simultaneously. The green found on the ceiling contains iron and aluminium; a particle that was examined showed a high peak for lead. This is comparable to the presumed paint splatter, as previously mentioned, but this small splatter is not found in any of the other samples, so the green layer below this splatter, which is visually different from it, must be a finishing layer that was applied during the green phase of the ceiling (see fig. 2.9). Those lighter green layers contain much lead white, which explains the lighter character of this colour. There is no other shade of green found in any of the samples; every light green is the same. In historic interiors it is often observed that profiles or the raised panel in the wainscot can have a different tone. In the book Het Nederlandse Interieur in Beeld doll’s houses from the end of the seventeenth and the first half of the eighteenth century are researched, because the interiors are not overpainted. Colours present in those interiors are moss green, brown, yellow, greyish white and diverse red colours like caput mortuum and light pink.35 Examples show all the woodwork in a room having different shades of one colour. In the Regentenkamer no difference in profiles of neither the red nor the green colour could be determined. Timeframe of colours found in the room
Year For the Regentenkamer Comment
1701 Remodelling of the room, red finishing layer (red) ochre >1750 Green finishing layers Naples yellow accessible >1847 Layer 12, a whitish layer is applied after this date Zinc white accessible >1950 Layer 17 is applied Titanium dioxide accessible ~1975 The room has a grey brown colour (based on the photograph) >1975 The contemporary turquoise colour 2.9 Conclusion The Arend Maartenshof was established in 1625, the colours of the interior of the Regentenkamer have not been recorded. It is known that in 1701 the room was remodelled, the chimney, wall panelling, portraits and ceiling piece were installed. Architectural paint research showed that during this time the walls were painted in a red colour, with ochre pigments, which is comparable to the red found on the ceiling. After 1750 and before 1847 the room must have been overpainted. The architectural borders of the ceiling were painted in a dark green. A paint splatter on the wall, found in sample number AMS08, shows the same layer, followed by light green layers. Those light green layers form the second finishing layer of the room. This green phase is the phase on which the reconstruction will be based. Because the paint of the ceiling cannot be removed or re-painted in red again, it is chosen to leave the ceiling green. The essence of the room is to be a unity; therefore the colour of the 35 Fock 2001: 98
Velzen, UvA, 2018 29 wall has to be related to the ceiling. By restoring the wall to the red phase this will not match with the ceiling. Therefore the green phase will be reconstructed, because this colour does match with the ceiling and increases the coherency of the room. Since there are no colour differences found in the profiles of the wall, there is no evidence that those were painted in a different shade. Following the green phase are whitish, grey and brown layers. It is hard to link those colours to a time frame, but archival information shows the room was painted greyish brown around 1975 (see appendix III). The colour turquoise is very present in the current interior of the Regentenkamer, but the colour found by architectural paint research appears to have a different tone. This lighter green colour will be the shown in the reconstructions.
Velzen, UvA, 2018 30
3 Translating colours into digital equivalents
The aim of this chapter is to assess how a colour can be converted into a digital code. For making a digital reconstruction the colours found through the architectural paint research must be converted into a digital variant. The digital reconstructions will offer an insight into the future restoration of the Regentenkamer. The first paragraph will discus how the human eye perceives colour. In the second paragraph different options are given for scanning a colour in an interior, giving advantages and disadvantages. The last paragraph will examine two paints applied in the Regentenkamer of the Arend Maartenshof and what the digital equivalents of those colours are. 3.1 Colour perception In order to explain how colour is seen by the human eye, it is useful to determine what colour is. A definition of colour by the Merriam Webster dictionary is: ‘a phenomenon of light (such as red, brown, pink, or grey) or visual perception that enables one to differentiate otherwise identical objects’.36 This definition describes the concept of colour as the difference between two objects which otherwise would be the same, as seen by the observer. Colour can be further characterized by hue, saturation and value. Hue is used to address the main colour term, for example yellow or red. Saturation indicates the chroma and tone, the purity of the colour. For example, if a colour is mixed with white, the colour becomes unsaturated, meaning it becomes paler and less intense. The third characteristic is value; this refers to the lightness of the colour. This depends on the light source present on the surface of the object.37 To perceive colour, first of all, a source of light is needed and an eye to receive the light. The retinal sensors of the human eye respond to the light coming in, this is done by three kinds of wave receptors: short, medium and long. The colours that overlap with those receptors, between long and short, are in the violet range. From short up to medium the blue, green and yellow can be seen; the red spectrum is between the medium to long range. This range can be converted into wavelengths; the visible spectrum is between 400nm and 700nm.38 Each colour emits its own wavelength and when entering the eye the cones are responsible for the processing of colour. The rods are functioning when there is less light, even in a near-dark environment we are able to see but not able to distinguish colours.39 Furthermore, there are many theories relating to vision and colour. For example; how colour functions in a room, the psychology of colour, and harmonies of colour. Besides, research has been carried out in colour vision differences between humans. A hue-scaling experiment was done, where participants had to scale different hues to a perfect gradient. This showed that not everyone scaled the colours in the same way. This is due to many factors, which means that parts of the colour circle can vary between observers.40 36 < https://www.merriam-webster.com/dictionary/color > 19th May 2018 37 < https://www.britannica.com/science/color#ref21839 > 19th May 2018 38 Best 2012: 5, 10 39 Rijgersberg 1967: 15 40 Emery et al. 2017: 63Velzen, UvA, 2018 31 Diverse aspects can influence the perception of colour, for example chromatic adaptation. This occurs when a white sheet of paper is seen in different lighting; the sheet of paper is still identified as white, even when the appearance of the paper is grey. The background area, the surroundings of the object can also disturb the recognition of colour.41 Colour can be further divided into two colour systems: the subtractive and additive colour system. The first is used for printing; cyan, magenta and yellow dyes absorb light and create colour. When the three dyes are mixed, the colours cancel each other, resulting in black.42 The latter is used for showing colour on screen, for example LED computer displays. Red, green and blue are combined to show any colour in one pixel. These colours add up to white. Because the displays emit light, any other source of light not originating from the display will distort the colour perception.43 The viewer will see the reconstruction of the Regentenkamer on a computer screen, so additive colour is perceived. The paint that is applied to the Regentenkamer is subtractive. Therefore it should be marked that during the restoration paint with subtractive character will be used. The challenge of converting the outcome of the colour measurement into a visually identical paint is not discussed in this thesis. 3.2 Colour evaluation for architectural paint research As mentioned in the first chapter, a method that has often been used in architectural paint research is making drawings of a room. In those drawings the colour of the former finishing layer is indicated with aquarelle or colour pencils. The colours of those physical mediums are limited, it is hard to achieve a correct duplication of the colour found through architectural paint research. A digital reconstruction has the advantage that there is no limitation in colours, since the whole visible spectrum can be shown on screen. Now the question is: how can a tangible colour be turned into its digital equivalent? One option is to match the investigated area to a colour fan deck. The idea is to find a colour that matches the area by visual comparison. As mentioned before, a drawback of this method is that the perception of hues of colour can differ between persons. A second drawback is the limited range of the colour fan deck. Whereas there are many colours to choose from, it is still limited in comparison with the full colour spectrum in digital programmes. In addition, the brightness, glossiness, texture and roughness are characteristics of the material appearance of the surface. It is not yet possible to scan and convert all of those at once into a digital platform. To get reading of the surface that is as close as possible, different methods can be used, as proposed in the article: ‘Color definition of open-air Architectural heritage and Archaeology artworks with the aim of conservation’.44 Holding a support next to the building and transcribing the colour can reproduce the surface colour of a building, a technique which is used in Italy to document buildings. This is very subjective, as the interpretation can differ amongst observers. Another method that is proposed in this article is a visual comparison with a colour fan deck, as explained earlier. Again the subjective character of this method is obvious. The third method that is mentioned is a diffuse reflectance measurement. 41 Best 2012: 182 42 Stone 2013: 163-166 43 Stone 2013: 138-139 44 Appolonio et al. 2017
Velzen, UvA, 2018 32 Devices like colorimeters, spectrophotometers and telephotometers can be used to scan an area. The advantages are that the devices give accurate colour data and can be taken on location. But if the object has a non-uniform colour many measurements are needed to get an appropriate colour lookup.45 3.3 Colours found in the case study For the colours assessment in the interior of the Regentenkamer two different methods were used to evaluate the colours. First of all the three colours were examined with a portable spectrophotometer, model CM-2600d, made by Konica Minolta. Before each measurement the spectrophotometer was calibrated to adjust the measurements to the surrounding light. The colour of an area was measured by holding this device against the flat surface. It was noticed that if the device couldn’t reach the surface, the given colour was not comparable with the original colours. For this research three areas were examined; the wainscoting with the current finishing layer and the revealed areas of the red phase and the green phase. For each layer the average out of three measurements was given in the CIELAB colour space system. This system was founded by the International Commission on Illumination, to objectively exchange colours worldwide.46 The CIELAB colour space is a system for organizing colours; each letter stands for one colour-space parameter. The L in LAB notes the lightness of the colour, between black and white, and gives a number from 0 to 100. The A channel is numbered from -128, the amount of green, to +127, the amount of red present in the sample. At last the B channel, from -128 to +127, correspondently determines the blue and yellow values of the measured colour.47 The detected colours were also checked with a colour fan deck; with the naked eye the colour of the surface was compared with the set colours in the fan deck. This was carried out for the revealed red and light green area (see table 3.1). The LAB values were switched to HEX codes to make it easier to insert them into the reconstruction programmes.48 45 Appolonio et al. 2017: 10-11 46 Best 2012: 179 47 Murali, Govindan 2013: 98 48 LAB values can also be inserted in the colour pickers, but it is faster to work with HEX codes.
Velzen, UvA, 2018 33 Table 3.1 Current finishing layer HEX code L* 52.36 #6F8178 a* -8.16 b* 2.54 Phase I colour HEX code L* 46.33 #8D6359 a* 16.22 b* 13.05 Measured from colour fan deck L* 57.60 #B57B77 a* 22.88 b* 11.74 Phase II colour HEX code L* 59.66 #88937E a* -7.4 b* 9.72 Measured from colour fan deck L* 65.86 #8DA790 a* -12.78 b* 8.79 The current turquoise colour is translated into a quite dark greyish green (see table 3.1). On location it was observed that not everywhere the same turquoise colour had been applied, corners or sections of the wall panelling had a different shade of colour. Moreover the lighting in the room alters the perception of the colour in comparison with the colour code achieved by the spectrophotometer. The colour of phase I was measured on the right side of the chimney, where a paint stratigraphy revealed the red layer (see fig. 3.1). The measurement with the spectrophotometer gave a greyish red colour (see table 3.1). When comparing this colour in Photoshop with the paint stratigraphy, it seemed to match the revealed colour (see fig. 3.1, square a). It was hard to reveal this red area while making the paint stratigraphy, because the paint layers were thin and the scalpel knife easily cut through it. This may have affected the reading of the spectrophotometer; nevertheless the colour does seem to visually match with the exposed red layer.
Velzen, UvA, 2018 34 Figure 3.1, paint stratigraphy, with squares of the colour evaluation For the second phase an exposed area on the left side of the chimney was measured with the spectrophotometer, again the area was not uniformly revealed. The LAB values of the colour were translated to a HEX colour code (see table 3.1). In this table the green appears to be quite dark, but compared with the exposed layer it does match with the original layer (see fig. 3.1, square b). Another factor that contributes to the misinterpretation of the colour measurement is the issue of the deteriorated colour found by the architectural paint research. Especially in oil paints the linseed oil can have been discoloured, or the pigment itself can age. It is known that lead white, ochre and Prussian blue can change over time.49 If this is the case for the Regentenkamer it should be acknowledged that the revealed colours might be aged. Therefore the intention of the original colour that was once applied can have been altered. Further testing was not possible in the timeframe of this research. 3.4 Conclusion The hue, saturation and value determine the appearance of a colour. Different wavelengths emitted in a space with light give a signal to the eye, that is how colour is perceived. It can be a challenge to convert a colour into a standardized code. Two popular methods are visual comparison and the use of colorimetric devices. Visual comparison can be subjective and differ between persons and the experience of that person. Colorimeters are more accurate, since different measurements can be taken and compared. For the evaluation of the case study the colours were examined with the spectrophotometer and with the naked eye. It was observed that the measurements with 49 Keijzer 2005: 90
Velzen, UvA, 2018 35 the spectrophotometer were the most accurate. The digital colour code was used in Photoshop to recreate the colours and match them with the colours found by the architectural paint research. The conclusion is that the colour codes are similar to the colours that were found. It is hard to say if this is the original colour, because during the architectural paint research it was difficult to get a uniform colour exposed. To conclude, the evaluation of colours is influenced by many factors, which make a truly objective reading very hard. The goal of this chapter was to provide information for making the digital reconstructions. The two colours of phase I and phase II were measured and translated into codes, when visually evaluated they seem to match with the revealed areas of the paint stratigraphy. Therefore the used colours will be #8D6359 for the red and for the green #88937E.
