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Authenticity screening of stained glass windows using optical spectroscopy

View Article: PubMed Central - PubMed

ABSTRACT

Civilized societies should safeguard their heritage as it plays an important role in community building. Moreover, past technologies often inspire new technology. Authenticity is besides conservation and restoration a key aspect in preserving our past, for example in museums when exposing showpieces. The classification of being authentic relies on an interdisciplinary approach integrating art historical and archaeological research complemented with applied research. In recent decades analytical dating tools are based on determining the raw materials used. However, the traditional applied non-portable, chemical techniques are destructive and time-consuming. Since museums oftentimes only consent to research actions which are completely non-destructive, optical spectroscopy might offer a solution. As a case-study we apply this technique on two stained glass panels for which the 14th century dating is nowadays questioned. With this research we were able to identify how simultaneous mapping of spectral signatures measured with a low cost optical spectrum analyser unveils information regarding the production period. The significance of this research extends beyond the re-dating of these panels to the 19th century as it provides an instant tool enabling immediate answering authenticity questions during the conservation process of stained glass, thereby providing the necessary data for solving deontological questions about heritage preservation.

No MeSH data available.


Colour values of all measured panes.All studied silver-yellow colours have a greenish, yellowish or orange hue on the CIE1931 colour diagram.
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f9: Colour values of all measured panes.All studied silver-yellow colours have a greenish, yellowish or orange hue on the CIE1931 colour diagram.

Mentions: A variety of mainly fabrication and material related parameters determine the final colour. At present only a few authors have applied the silver stain process on custom-made glasses in order to unveil the fabrication techniques in medieval times. The limited amount of research at this stage makes a decision about fabrication conditions and corresponding period based on colour and spectral shapes difficult. However, since each fabrication condition (glass type, paint type and concentration, firing temperature and time) leads to a characteristic spectral fingerprint we compared the colour and spectral shapes of all SY1–4 stained glasses with those of ancient fragments found in literature. The glass compositions of these fragments include HLLA and mixed-alkali; two of the three major glass types used between 800–1800 AD. It concerns ten HLLA fragments from two Spanish (Avila & Palencia)6 (Avi15, Avi16 and Pal15) and one Belgian (Bruges)38 location together with three (O3, O5 and O13) mixed-alkali pieces from Tomar (Portugal)37. The HLLA samples from Bruges are further classified in HLLA1 and HLLA2 following their differences in alkali metal concentration levels. Chemical data is given in Supplementary Table 2. Three observations are made. (1) Apart from the two samples originating from Avila, the calculated colour values group all fragments in three separate classes characterized by a greenish-yellow, yellow or orange colour (Fig. 9). (2) Secondly, it is perceived that the colour values as well as the entire spectral shape of the three mixed-alkali fragments correspond pretty well with the stained fragments of the two studied panels. (3) Finally, it is concluded that the standard deviations on the spectral properties (error flags in Fig. 10) of the latter are much smaller compared to the two HLLA groups of post-medieval material. This points out a better controlled fabrication process potentially implying a more recent production.


Authenticity screening of stained glass windows using optical spectroscopy
Colour values of all measured panes.All studied silver-yellow colours have a greenish, yellowish or orange hue on the CIE1931 colour diagram.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121600&req=5

f9: Colour values of all measured panes.All studied silver-yellow colours have a greenish, yellowish or orange hue on the CIE1931 colour diagram.
Mentions: A variety of mainly fabrication and material related parameters determine the final colour. At present only a few authors have applied the silver stain process on custom-made glasses in order to unveil the fabrication techniques in medieval times. The limited amount of research at this stage makes a decision about fabrication conditions and corresponding period based on colour and spectral shapes difficult. However, since each fabrication condition (glass type, paint type and concentration, firing temperature and time) leads to a characteristic spectral fingerprint we compared the colour and spectral shapes of all SY1–4 stained glasses with those of ancient fragments found in literature. The glass compositions of these fragments include HLLA and mixed-alkali; two of the three major glass types used between 800–1800 AD. It concerns ten HLLA fragments from two Spanish (Avila & Palencia)6 (Avi15, Avi16 and Pal15) and one Belgian (Bruges)38 location together with three (O3, O5 and O13) mixed-alkali pieces from Tomar (Portugal)37. The HLLA samples from Bruges are further classified in HLLA1 and HLLA2 following their differences in alkali metal concentration levels. Chemical data is given in Supplementary Table 2. Three observations are made. (1) Apart from the two samples originating from Avila, the calculated colour values group all fragments in three separate classes characterized by a greenish-yellow, yellow or orange colour (Fig. 9). (2) Secondly, it is perceived that the colour values as well as the entire spectral shape of the three mixed-alkali fragments correspond pretty well with the stained fragments of the two studied panels. (3) Finally, it is concluded that the standard deviations on the spectral properties (error flags in Fig. 10) of the latter are much smaller compared to the two HLLA groups of post-medieval material. This points out a better controlled fabrication process potentially implying a more recent production.

View Article: PubMed Central - PubMed

ABSTRACT

Civilized societies should safeguard their heritage as it plays an important role in community building. Moreover, past technologies often inspire new technology. Authenticity is besides conservation and restoration a key aspect in preserving our past, for example in museums when exposing showpieces. The classification of being authentic relies on an interdisciplinary approach integrating art historical and archaeological research complemented with applied research. In recent decades analytical dating tools are based on determining the raw materials used. However, the traditional applied non-portable, chemical techniques are destructive and time-consuming. Since museums oftentimes only consent to research actions which are completely non-destructive, optical spectroscopy might offer a solution. As a case-study we apply this technique on two stained glass panels for which the 14th century dating is nowadays questioned. With this research we were able to identify how simultaneous mapping of spectral signatures measured with a low cost optical spectrum analyser unveils information regarding the production period. The significance of this research extends beyond the re-dating of these panels to the 19th century as it provides an instant tool enabling immediate answering authenticity questions during the conservation process of stained glass, thereby providing the necessary data for solving deontological questions about heritage preservation.

No MeSH data available.