Cultural and architectural heritage conservation and restoration: which colour?

Abstract

Colours play a crucial role in the field of architectural heritage. Colour analysis and colour rendition are involved in several critical facets of heritage preservation, conservation and restoration. These aspects are related to accurate documentation and an accurate representation of heritage artefacts and architectural works. The aim of this paper is to describe critical issues and open problems of the processes involved in this field. Documentation is performed in multiple ways, acquiring heterogeneous data ranging from archival images, photographs, drawings using various consumer or professional instruments (eg, digital cameras and spectrophotometers). The reliability of colour acquisition might be influenced by instrumental reasons (the technology used to acquire colour information), by environmental changes (architectural heritage surveys are often performed outdoors), by morphology (complex architectural objects are characterised by concavities and convexities which complicate the reflection evaluation), or by materials (showing different reflection, porosity and transparency indexes). Identification of materials, such as colorants, pigments and dyes, is also a vital process in the heritage field. Colour information could be used as an approach to the identification of materials, but these methods are still under development, and many issues need to be solved to achieve reliable results. Visualisation techniques of a heritage artefact also present the problem of the correctness of the colour representation. Several problems need to be faced in this context: the reliability of the acquisition, colour management of the rendering software, model complexity, and fragmentation of the devices upon which the model is visualised.

Color mapping of the building façades in the historical urban fabric: The Ayazini village civil architectural examples

“…What are the color mixtures found within the colors obtained should be determined 16,19,21 . A classification of the colors perceived should be conducted by making this process through the applications of photographic processing with computer technologies 23 …”

“…16,19,21 A classification of the colors perceived should be conducted by making this process through the applications of photographic processing with computer technologies. 23 There are changes in the colors of the Ayazini tufa connected to the environmental and atmospheric effects of the tufa. These changes stem from the cellular structure and from containing natural moisture of the tufa.…”

“…However, since these studies were not developed compared to the computer technologies of the present day, it can be stated that they remained at a basic level. It was expressed by Gaiani et al 23 that the computer technologies produced more appropriate results in the determination of colors and that it provided facility in the documentation of colors. According to what was quoted by Sibillano, 24 one of the research studies with a broad scope conducted in this field was the Zurich city color master plan made by the Zurich City Planning Unit.…”

“…In the restoration activities related to color, 23 it was stated that colors in restoration are an important element in the preservation of the cultural heritage. It was emphasized that producing the palette of colors in historical buildings should be taken into consideration in restoration activities that would be made in landscape and architecture.…”

Physical and Chemical Characterisation of the Pigments of a 17th-Century Mural Painting in the Spanish Caribbean

“…The technological progress of the last few decades has favoured the study of colours and guaranteed the accuracy of results under certain measuring conditions. Although colour information provides an approach to the identification of pigments, colour detection may be influenced by the effects of environment on outdoor measurements, by the morphology in the case of objects with concavities and convexities, which complicate the analysis, or by material changes [6]. For example, illumination of an object from different orientations can give rise to different colour perceptions.…”