published by A PORTABLE MICRO-FADING SPECTROMETER FOR VERSATILE LIGHTFASTNESS TESTING

ISSN: 1581-9280 web edition ISSN: 1854-3928 print edition www.Morana-rtd.com © by M O R A N A RTD d.o.o. The design and experimental method for the use of a novel instrument for lightfastness measurements on an artwork is presented. The new micro-fading spectrometer design offers increased structural stability (which enables porta-bility) and increased versatility over the previous, published design, broadening the scope of locations at which data can be acquired. This reduces the need for art handling or transportation in order to gain evidence-based risk assess-ments for the display of light-sensitive artworks. The instrument focuses a stabilized high powered xenon lamp to a spot 0.25 mm diameter (FWHM) while simultaneously monitoring colour and spectral change. This makes it pos-sible to identify pigments and determine the lightfastness of materials effectively and non-destructively. With 2.59 mW or 0.82 lumen (1.7 · 107 lux for a 0.25 mm focused spot) the instrument is capable of fading Blue Wool 1 to a measured 11 ΔEab value (using CIE standard illuminant D65) in 15 min. The temperature increase created by focused radiation was measured to be 3 to 4 °C above room temper-ature. The system was stable within 0.12 ΔEab over 1 h and 0.31 ΔEab over 7 h. A safety evaluation of the technique is discussed which concludes that some caution should be employed when fading smooth, uniform areas of artworks. The instrument can also incorporate a linear variable filter. This enables the researcher to identify the active wave-bands that cause certain degradation reactions and deter-mine the degree of wavelength dependence of fading. Some preliminary results of fading experiments on Prussian blue samples from the studio materials of J. M. W Turner (1755-1851) are presented.