ARCHES research group

3D technologies, including data acquisition, digital modelling and manufacturing, have been used in the context of cultural heritage (CH) since the 1990 s. A general state of the art is given concerning the adoption of 3D models in CH and for virtual reconstruction of missing parts in conservation-restoration work. Although an increased use of 3D technologies is noticed in research, preservation, dissemination and conservation-restoration, the opinion, experience and concerns of the restorer on the application of 3D technologies in their work is unclear. The conservation community was therefore asked to complete an online questionnaire (n = 153) and a literature study provided 65 case studies to demonstrate the practical use of 3D technologies for loss compensation. The results of the questionnaire showed a positive trend towards 3D technologies in restoration projects. Seven main concerns were distinguished in the survey and further discussed by means of the case studies: (i) The printing process and materials, (ii) the necessary knowledge, (iii) the applicability, (iv) ethical considerations, (v) required work and costs, (vi) managing and storing data and (vii) the achieved results. Although the main concerns are justified as there are many challenges to overcome, reassurance or first answers to these concerns have been found in the varied applications of 3D technologies presented in the case studies. The arguments pro and con 3D technologies, possible solutions for the mentioned concerns and further research possibilities are subsequently presented in informative mind maps. This article and the accompanying mind maps can as such assist the restorer in decision-making when considering using 3D technologies in restoration projects.

Vanuit de problematiek verbonden aan de restauratie van fragiel kantporselein, wordt onderzocht hoe 3D-technologie dienst kan doen bij de aanvulling van een casusobject. De lacunes in het casusobject kunnen moeilijk tot onmogelijk manueel gerestaureerd worden gezien het om een uiterst fijne porseleinen stofimitatie gaat. Kantporselein is vervaardigd door echt kant in een porseleinen slip te dippen en vervolgens te bakken op hoge temperatuur. Een aanzet tot restauratie wordt gegeven door de implementatie van 3D-scannen, 3D-modelleren en 3D-printen. Tijdens iedere fase wordt naar de meest geschikte state-of-the-art methode gezocht, binnen de beschikbare opties. Voor het 3D-scannen bleek (micro)computertomografie de beste optie omdat zo het hele volume gedetailleerd in beeld kan worden gebracht. De aanvullingen werden gemodelleerd met Rhinoceros 5.0 in combinatie met manuele technieken. De 3D-modellen werden met een PolyJet-printer getest en de prototypes werd geprint door Materialise, Leuven. De in deze casus gebruikte methodes illustreren dat een digitale workflow een cruciale rol kan spelen om fijne en accurate resultaten te bereiken, maar ook dat manuele methodes noodzakelijk blijven in het restauratieproces.

Starting with the complex nature of drape lace mounted on porcelain figurines, methods of 3D technology for use in restoration were examined in a pilot study. A porcelain figure group, including a lady wearing a porcelain lace dress with many lacunae was chosen for testing (Figure 1). The dress exists of an extremely fine lace imitation, made with real lace dipped in porcelain slip, mounted in place before firing. Because of the intricate details, small scale, and fragile nature, the dress cannot be easily restored manually without risking further damage.

Over the past decade, the use of 3D scanning, virtual reconstruction and digital manufacturing in the preservation of cultural heritage (CH) has gained significant attention, among other for the restorative intervention of loss compensation. These techniques have been explored both in conservation-restoration (CR) practices and research facilities. However, despite this progress, there is a notable absence of an educational framework specifically designed for virtual restoration methods aimed at physical restoration. As a result, CR practitioners motivated to execute a virtual restoration are either challenged to find their way in a wealth of information or have to rely on 3D experts for guidance and digital tasks. This article discusses this gap by detailing the construction and validation of an educational framework for loss compensation on CH objects. Drawing upon an extensive review of past case studies, an "Overview of possibilities on the application of 3D technologies for restoration of CH objects" (shortened to Overview OP) is compiled of involved reasons, processes, methods and materials to consider within a virtual restoration workflow. The composed Overview consists of eight phases, distinguishing 22 steps, encompassing both traditional restorations steps, virtual steps and combined steps in which material, object, device and product-related possibilities are displayed. To assess its effectiveness, an experimental setup was devised, incorporating a pre and post-test, short-term and long-term usability testing, and an evaluation questionnaire. This setup was implemented within an educational context involving third-year bachelor students in CR at the University of Antwerp (n = 17). Although the Overview OP does require a learning curve and may initially appear overwhelming, the experimental results demonstrated it organisational structure. It was found to be highly useful, timesaving and capable of efficiently guiding CR practitioners towards relevant information tailored to their specific cases. Following the validation process, the Overview OP was improved based on the received feedback. Additionally, a literature update was conducted, expanding the Overview OP to include cases executed between 2020 and 2023. The finalised version, along with the accompanying "Inventory of cases" is now accessible open-source on an online platform.

Emerging technologies offer many advantages for cultural heritage preservation, and as such, 3D technologies can also be considered a new tool in the conservator-restorer’s toolbox. 3D scanning and printing are particularly useful for reconstructing missing parts on cultural heritage objects. However, the application of these innovative methods and materials is difficult for inexperienced users such as emerging, academic and professional restorers. The aim of this research is to make 3D technologies more comprehensible, by bridging the gap between the restorers’ expertise and 3D specialists, and to make them more applicable to the restoration practice, by aligning 3D technologies to the needs of restoration theory and practice. The research has enabled the construction of a digital toolbox, containing relevant information and previous case studies to guide the target audience in the generation of knowledge on the applied and suitable use of 3D technologies for loss compensation of missing parts. This toolbox consists out of three tools and is presented online on www.3drestorationtoolbox.com: the first tool, the Mind maps for decisionmaking, lay out the documented pros and cons of using 3D technologies, the second tool is an Overview of possibilities, which guides the restorer in a 3D restoration workflow that combines traditional, digital, and hybrid restoration methodologies, and the third tool is an Inventory of cases of the cases consulted in the other tools. This dissertation and the 3D Restoration Toolbox are as such presented as a contribution to the integrated implementation of 3D technologies in the restoration practice.