5 research outputs found
Appearance Changes due to Light Exposure
The fading of materials due to light exposure over time is a major contributor to the overall aged
appearance of man-made objects. Although much attention has been devoted to the modeling of
aging and weathering phenomena over the last decade, comparatively little attention has been paid
to fading effects. In this dissertation, we present a theoretical framework for the physically-based
simulation of time-dependent spectral changes induced by absorbed radiation. This framework
relies on the general volumetric radiative transfer theory, and it employs a physicochemical approach
to account for variations in the absorptive properties of colourants. Employing this framework, a
layered fading model that can be readily integrated into existing rendering systems is developed
using the Kubelka-Munk theory. We evaluate its correctness through comparisons of measured
and simulated fading results. Challenges in the acquisition of reliable measurements are discussed.
The performance characteristics of the proposed model are analysed, and techniques for improving
the runtime cost are outlined. Finally, we demonstrate the effectiveness of this model through
renderings depicting typical fading scenarios
X-ray fluorescence applied to yellow pigments based on lead, tin and antimony: comparison of laboratory and portable instrumentation
X-ray fluorescence is a diagnostic approach particularly suited to be utilized in cultural
heritage sector since it falls in the non-destructive and non-invasive analytical tools. However
there are big differences between portable and laboratory instrumentation that make difficult
to perform a comparison in terms of quality and reliability of the results. The present study is
specifically addressed to investigate these differences in respect of the same analytical
sample-set. To reach this goal a comparison was thus carried out between portable and bench
top devices X-ray fluorescence devices and techniques were used on different type of yellow
pigments based on lead, tin and antimony obtained in laboratory, reproducing the instructions
described in “old” recipes, that is: i) mortar of lead and tin produced on the basis of the recipe
13 /c V of the “Manuscript of Danzica” and “ Li tre libri dell’arte del Vasaio” by Cipriano
Piccolpasso; ii) two types of lead and tin yellow (Pb2SnO4 and PbSnO3) produced starting
from the indications of the 272 and 273 recipes of the “Bolognese Manuscript”; iii) lead
antimonate (Pb2Sb2O7) obtained by following the instructions of the Piccolpasso’s treatise
and those contained on the “Istoria delle pitture in maiolica fatte in Pesaro e ne’ luoghi
circonvicini di Giambattista Passeri” and finally iv) lead, tin and antimony yellow
(Pb2SnSbO6,5) obtained starting from the information contained in the paper 30 R of
“Manuscript of Danzica” [1].
The XRF analysis were performed using a laboratory instrumentation (Bruker M4 Tornado)
and a handset analytical device (Assing Surface Monitor). In order to perform a significant
statistical comparison among acquired and processed data, all the analyses have been carried
out utilizing the same sample, the same acquisition set up and operative conditions.
A chemometric approach, based on the utilization of Principal Component Analysis (PCA)
and multivariate analytical based tools [2], was utilized in order to verify the spectral
differences, and related informative content, among the different produced yellow pigments.
The multivariate approach on the results revealed instrumental differences between the two
systems and allowed to compare the common characteristics of the set of pigments analyzed
Colour and Colorimetry Multidisciplinary Contributions Vol. XIb
It is well known that the subject of colour has an impact on a range of disciplines. Colour has been studied in depth for many centuries, and as well as contributing to theoretical and scientific knowledge, there have been significant developments in applied colour research, which has many implications for the wider socio-economic community. At the 7th Convention of Colorimetry in Parma, on the 1st October 2004, as an evolution of the previous SIOF Group of Colorimetry and Reflectoscopy founded in 1995, the "Gruppo del Colore" was established. The objective was to encourage multi and interdisciplinary collaboration and networking between people in Italy that addresses problems and issues on colour and illumination from a professional, cultural and scientific point of view. On the 16th of September 2011 in Rome, in occasion of the VII Color Conference, the members assembly decided to vote for the autonomy of the group. The autonomy of the Association has been achieved in early 2012. These are the proceedings of the English sessions of the XI Conferenza del Colore