This work proposes a multi-method approach that combines advanced microscopy (SEM/EDX, AFM) and spectroscopy (UV-vis and FTIR) techniques. This approach not only characterises the behaviour of the additives of two commercial poly(vinyl acetate) (PVAc) and acrylic emulsion paints but also simultaneously characterises the changes in chemical composition and morphology observed in the paint films as a result of ageing due to the paints being exposed to an intense source of simulated daylight. In parallel, a series of mechanical tests were performed that correlate the chemical changes in composition and the changes observed in the films' mechanical properties. This work was a comparative study between both types of acrylic and PVAc paints. The results obtained are of great interest for the modern paint conservation field as they provide valuable information on the mid- and long-term behaviours of these synthetic paints.
-This paper faces the problem of acquiring archaeological artifacts using triangulation based 3D laser scanners and focusing on reflective/refractive surfaces. This kind of artifacts are mostly made of glass or polished metal, and the properties of their surfaces violate most of the fundamental assumptions made by vision algorithms. Also, the unique and fragile nature of archaeological artifacts adds an extra limitation to the acquisition process: using industrial whitening sprays has to be avoided, due to the physicochemical processes required to clean the surface after scanning and because the chemical properties of these sprays may damage the original object. As an alternative to them, a new application of a common conservation material is proposed: the use of cyclododecane as a whitening spray. Thanks to its chemical stability and to the fact that it sublimes at room temperature, together with its good film-forming capabilities, a set of evaluation tests is presented to prove that the error introduced by the opaque thin layer created on the surface of the artifact is smaller than the accuracy of the 3D scanner and, thus, no acquisition errors are introduced. A comparison with general-purpose industrial whitening sprays is also presented, and achieved results show no significant differences in the quality of the resulting 3D models.
Resumen:En este artículo se restaura un cuenco de vidrio del siglo XVI-XVII mediante la creación de su modelo tridimensional (3D) con el fin de operar con él y eliminar el riesgo que entraña la manipulación de objetos frágiles. La áreas faltantes, correspondientes a los fragmentos de vidrio no encontrados en la excavación, se han llevado a cabo mediante la construcción digital de implantes. Para elaborar los implantes se ha duplicado un volumen del modelo 3D del cuenco adaptándolo al espacio confinado en las áreas vacías. La impresión de los implantes se ha hecho con filamento acrilonitrilo butadieno estireno (ABS). Estos implantes, que sustituyen a las zonas perdidas, han devuelto la estabilidad a la pieza y han permitido recrear la morfología original. El resultado puede ser comparado al obtenido por métodos tradicionales, pero difiere en que requiere una mínima manipulación del objeto, contribuyendo así, a la preservación y salvaguarda del objeto restaurado. Este método no invasivo se ofrece como un tratamiento alternativo, donde el objeto arqueológico es sustituido por su modelo virtual en todas las fases del proceso posteriores a la captura de datos 3D. No se han encontrado diferencias significativas en cuanto a los resultados obtenidos de impresión 3D con los dos tipos de filamentos ensayados (blanco y translúcido). Palabras clave: vidrio arqueológico, reconstrucción 3D, modelado 3D, impresión 3D, restauración Abstract:This article describes the restoration of a glass bowl from the 16 th -17 th century by creating its three-dimensional (3D) model. The final purpose is to work with this model in order to avoid damaging situations that are associated with the manipulation of fragile objects. The gap areas, those corresponding to the missing fragments not found in the excavation, were carried out by constructing digital implants. A restricted area of the 3D model has been duplicated in order to accommodate it to confined intervals of the gap. The final implants were printed with acrylonitrile butadiene styrene (ABS) filament. These implants replace the lost areas and give stability back to the item by recovering the original morphology. The result can be compared with the outcome obtained by a traditional process, but differs due to the fact that requires minimum manipulation of the item, so it can contribute to preserve and safeguard the restored object. This is a non-invasive method which is offered as an alternative treatment, where the archaeological object is replaced by its virtual model in the steps of the process after 3D data acquisition. Significant differences have not been found in the 3D printing results obtained with the two types of filaments tested (white and clear).Key words: archaeological glass, 3D reconstruction, 3D modelling, 3D printing, restoration IntroducciónUna gran parte del vidrio arqueológico exhumado presenta un deterioro característico con indicadores claros de las condiciones de elevada humedad con la que ha interactuado durante años. Su extracción conlleva una rápida deshidrat...
This paper deals with storage and transportation of fragile heritage objets. The main goal is to create an ad-hoc packaging software solution by combining the use of 3D scanning and 3D milling technologies. Traditionally, packaging for this kind of objects is made manually, creating custom supports and boxes adapted to the specific needs and particularities of each case. This process is time-consuming and fully dependent on the conservator's skills. On the other hand, the proposed solution provides a faster execution and a standard solution adapted to every object. The process starts with the acquisition of 3D digital models of the original artifacts and uses an interactive GPU-accelerated algorithm to assist the conservator in the construction of the package. The final result is a CNC program that is sent to a low cost milling machine to produce the housing for the selected artifact. Unlike 3D printers, milling machines allow working with lots of different materials, which is a key aspect for this kind of packages: chemical stability and shock absorption are mandatory. Given that, during the design process, original artifacts are only manipulated in the acquisition stage, risks of damaging them are also reduced. Since the whole process is considered in the same application, intermediate calculations are performed considering manufacturing and user-defined restrictions. This way, together with a GPU implementation, achieved results are very fast providing a real-time application with visual feed-back.
This paper describes the virtual reconstruction of a late fifteenth century terracotta statue. The proposed solution was adopted during the restoration process when it was not possible to get back the fragments from the missing parts that were lost during the burial period. The archaeological statue that has been called 'Crist del Fossar', according to its morphology and provenance, was found severely damaged, as it appeared highly fragmented with dull and age-worn edges. The restoration was assisted by means of an automatic reassembly technique that operates on digital models of fragments. This technique considers the best alignments between themselves (without the need to manipulate the original ones) and leads the reassembly and adhesion processes of the fragments. The statue will be part of a temporary exhibition at the Museu de Prehistòria de València where visitors would be able to appreciate the restoration of the few fragments that have been conserved and will be able to explore the virtual reconstruction of the entire statue through an immersive 3D interactive visualization
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