DOI issue:
Artykuł i prace konserwatorskie
DOI article:Röhrs, Stefan: Krakow's Laboratory of Analysis and Non-Destructive Investigation of Heritage Objects (LANBOZ) and Berlin's Rathgen-Forschungslabor (RF): an exemplary European collaboration DOI: an exemplary European collaboration
DOI Page / Citation link: https://doi.org/10.11588/diglit.49248#0090
STEFAN RÓHRS
together with Michał Łukomski and Roman Kozłowski from the Polish Academy of Sciences (PAN), partici-
pated in the conference “Heritage Science and Sustainable Development for the Preservation of Art and
Cultural Assets - on the Way to the Green Museum” held at the Pergamon Museum, Berlin, on 11-12 April
2013 (Rathgen-Forschungslabor 2013). This conference was supported by the Deutsche Forschungsge-
meinschaft and marked the 125th anniversary of the scientific laboratory of the Berlin Museums. Among
many papers, the following were presented by the MNK: “Allowable microclimate variations in museums
and historic buildings: Reviewing the guidelines” and “Saving Energy in the National Museum in Krakow,
Poland - A case of green climate management.”
COLLABORATION ON MFT
88 The network, Colour and Space in Cultural Heritage (COSCH), supported by the EU-funded programme
Cooperation for Science and Technology (COST), provided another opportunity for collaboration. This
research network aimed to foster knowledge of documentation of cultural heritage artefacts as true to
the object and precise as possible. LANBOZ and RF focused on the assessment of the photostability of
cultural heritage objects. Within the framework of COSCH Working Group 4, researching the analysis and
restoration of cultural heritage surfaces and objects, Julio M. del Hoyo-Melendez of LANBOZ came for
a week-long Short Term Scientific Mission (STSM) to Berlin's RF in November 2013. The aim of this STSM
was to establish standard working practices between the two institutions and to enhance mutual knowl-
edge of the application of the Micro-Fading Test (MFT). An outcome of this STSM was a joint publication,
in collaboration with Lore Troalen of the National Museum Scotland, on the photostability of Subarctic
Athapaskan colouring of quillwork (Troalen et al. 2015).
Both institutions apply the MFT to study the photostability of cultural heritage objects. The MFT uses
a small light spot (0.4 mm in diameter) in order to measure the light sensitivity of an object (Morales-
Merino et al. 2016). The MFT records continuously reflected spectra, as well as colour information, for
several minutes. With these values, it is possible to relate a change in the colour to the amount of light
(exposure given in lux hours). The colour difference is expressed in AE. In terms of experimental param-
eters, both laboratories have agreed upon the use of the D-55 illuminant and the 2-degree observer
when conducting microfading measurements.
The results generated by this method are sometimes poor. Therefore, comparison studies become
necessary for cultural institutions, especially if the use of this technique is to become a standard practice
in assessing the photostability in the future. The method relies upon reciprocity, and deviations from the
reciprocity principle in the experiment are difficult to interpret. Reciprocity in this context means that
the colour change is independent of the illumination level and only depends on the exposure (which is
the product of illumination by time). In Fig. 1, measurements of Blue Wool (BW) standards for estimating
the photostability in the RF by different illumination levels are shown, resulting in an identical colour
difference (within the margin of the experimental error) at the same exposure, and therefore fu Ifi Hi ng the
reciprocity principle. It is suspected that this may not hold for all materials and all illumination levels
(del Hoyo-Melendez and Mecklenburg 2011).
During the STSM research into reciprocity behaviour of materials, a comparison study was carried out.
For the comparison study, materials were analysed by MFT using micro fading spectrometers in Krakow
and in Berlin. The materials were a set of samples provided by Bruce Ford, an internationally recogni-
sed expert in microfading. The results are shown in Fig. 2. It can be observed that when using the RF
instrument in Berlin, the highly light-sensitive materials (BW 1-2 range) always gave a higher response
as compared to the one in Krakow (LANBOZ). The opposite was observed at the lower sensitivity end (BW
3). Apart from experimental variability of the results induced by sample age and sample positioning,
some of the possible justifications for this difference could be the difference in the light source. RF uses
a xenon arc lamp, while LANBOZ uses a high-power solid-state plasma light source. Samples with photo-
stability within the BW 2-3 range seem to be more affected by the light source installed in the LANBOZ
instrument. Variations in relative humidity can also change the results of the lightfastness test, including
the behaviour of the Blue Wool material, and should also be taken into account.
together with Michał Łukomski and Roman Kozłowski from the Polish Academy of Sciences (PAN), partici-
pated in the conference “Heritage Science and Sustainable Development for the Preservation of Art and
Cultural Assets - on the Way to the Green Museum” held at the Pergamon Museum, Berlin, on 11-12 April
2013 (Rathgen-Forschungslabor 2013). This conference was supported by the Deutsche Forschungsge-
meinschaft and marked the 125th anniversary of the scientific laboratory of the Berlin Museums. Among
many papers, the following were presented by the MNK: “Allowable microclimate variations in museums
and historic buildings: Reviewing the guidelines” and “Saving Energy in the National Museum in Krakow,
Poland - A case of green climate management.”
COLLABORATION ON MFT
88 The network, Colour and Space in Cultural Heritage (COSCH), supported by the EU-funded programme
Cooperation for Science and Technology (COST), provided another opportunity for collaboration. This
research network aimed to foster knowledge of documentation of cultural heritage artefacts as true to
the object and precise as possible. LANBOZ and RF focused on the assessment of the photostability of
cultural heritage objects. Within the framework of COSCH Working Group 4, researching the analysis and
restoration of cultural heritage surfaces and objects, Julio M. del Hoyo-Melendez of LANBOZ came for
a week-long Short Term Scientific Mission (STSM) to Berlin's RF in November 2013. The aim of this STSM
was to establish standard working practices between the two institutions and to enhance mutual knowl-
edge of the application of the Micro-Fading Test (MFT). An outcome of this STSM was a joint publication,
in collaboration with Lore Troalen of the National Museum Scotland, on the photostability of Subarctic
Athapaskan colouring of quillwork (Troalen et al. 2015).
Both institutions apply the MFT to study the photostability of cultural heritage objects. The MFT uses
a small light spot (0.4 mm in diameter) in order to measure the light sensitivity of an object (Morales-
Merino et al. 2016). The MFT records continuously reflected spectra, as well as colour information, for
several minutes. With these values, it is possible to relate a change in the colour to the amount of light
(exposure given in lux hours). The colour difference is expressed in AE. In terms of experimental param-
eters, both laboratories have agreed upon the use of the D-55 illuminant and the 2-degree observer
when conducting microfading measurements.
The results generated by this method are sometimes poor. Therefore, comparison studies become
necessary for cultural institutions, especially if the use of this technique is to become a standard practice
in assessing the photostability in the future. The method relies upon reciprocity, and deviations from the
reciprocity principle in the experiment are difficult to interpret. Reciprocity in this context means that
the colour change is independent of the illumination level and only depends on the exposure (which is
the product of illumination by time). In Fig. 1, measurements of Blue Wool (BW) standards for estimating
the photostability in the RF by different illumination levels are shown, resulting in an identical colour
difference (within the margin of the experimental error) at the same exposure, and therefore fu Ifi Hi ng the
reciprocity principle. It is suspected that this may not hold for all materials and all illumination levels
(del Hoyo-Melendez and Mecklenburg 2011).
During the STSM research into reciprocity behaviour of materials, a comparison study was carried out.
For the comparison study, materials were analysed by MFT using micro fading spectrometers in Krakow
and in Berlin. The materials were a set of samples provided by Bruce Ford, an internationally recogni-
sed expert in microfading. The results are shown in Fig. 2. It can be observed that when using the RF
instrument in Berlin, the highly light-sensitive materials (BW 1-2 range) always gave a higher response
as compared to the one in Krakow (LANBOZ). The opposite was observed at the lower sensitivity end (BW
3). Apart from experimental variability of the results induced by sample age and sample positioning,
some of the possible justifications for this difference could be the difference in the light source. RF uses
a xenon arc lamp, while LANBOZ uses a high-power solid-state plasma light source. Samples with photo-
stability within the BW 2-3 range seem to be more affected by the light source installed in the LANBOZ
instrument. Variations in relative humidity can also change the results of the lightfastness test, including
the behaviour of the Blue Wool material, and should also be taken into account.