Dear all,

I am pleased to invite you to the defence of my PhD thesis “Material Appearance for Conservation and Restoration – Capturing and modelling the appearance of gilded surfaces“, supervised by Clotilde Boust and Jon Yngve Hardeberg, at the research department at the Centre of Research and Restoration for the Museums of France, and the Colourlab at the Norwegian University of Science and Technology.

The defence will take place on Friday, 28^th of April, 2023 at 2 pm in the Palissy Auditorium at C2RMF (Porte des Lions, Palais du Louvre, 14 quai François Mitterand, 75001 Paris). 

As part of the PhD evaluation, I will be giving a lecture “Gloss in cultural heritage preservation: expectations, challenges and innovations”. The lecture will take place on the same date at 10 am in the Palissy auditorium.

Both the lecture and PhD defence will also be available online via the link below:

Click here to join the meeting

Meeting ID: 362 760 897 724
Passcode: Rn9Q5w
Looking forward to seeing you there,

Yoko Arteaga 

PhD student – CHANGE ITN 
Imaging group
C2RMF – Centre de recherche et restauration des musées de France 

Abstract

The human visual system is extremely efficient at identifying and recognising different materials. Rarely do humans mistake one material for another, and the appearance of a material tells us many important
cues about the environment we live in. However, the mechanisms behind material appearance and perception are not fully understood.
Cultural heritage objects exist in a wide range of materials, each with its own particular appearance.
While it is common to evaluate the colour of cultural heritage objects before and after restoration, this is not always representative of perceptual differences that the restoration may cause. Gilding is a form
of polychromy commonly used in the Middle Ages which poses many technical challenges to acquire its appearance. The gold leaf, of metallic nature, creates a particular appearance which changes depending on the fabrication method and has a strong angular dependence. This thesis aims to address some of these issues, by acquiring, modelling, and analysing the appearance of complex cultural heritage materials. Focus is given to gilded surfaces since they exhibit interesting appearance
properties such as gloss, metallicity, and in some cases even translucency. The research is divided into two sub-objectives, one concerning methods for appearance capture, and the second deals with
applying material appearance analysis for conservation and restoration.
The first research domain of this PhD thesis deals with methods for material appearance capture. First, the challenges and limitations of using conventional methods for appearance capture are explored. As
an alternative, an imaging-based methodology is developed and evaluated for bidirectional reflectance measurements, catered for cultural heritage materials of challenging appearance. This method is then applied to satisfy the second sub-objective.
The second research domain concerns the application of material appearance analysis for conservation. For this, the appearance of different types of gilding is acquired, modelled, and
evaluated. By using perceptual gloss metrics, the different types of gilding can be described and characterised in terms of perceptual differences. Moreover, varnish removal methods are evaluated in
terms of appearance change, to guide the conservation of a 15th century painted panel.

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