THE EFFECT OF pH OF THE PAPER SUPPORT ON THE FADING OF CARMINE WATERCOLOR

Strumfels, Yoonjoo; Berrie, Barbara H.

doi:10.1179/sic.2002.018

Cited by 1 publication

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“…In experiments carried out in buffer solutions of a range of pH values, it was found that the characteristic absorption lines of cochineal and lac were less prominent and were blue shifted in acidic solutions [36][37]. Colour changes were also observed when cochineal was painted on paper of different pH values [38]. UV-fluorescence spectroscopy is also one of the common techniques for detecting organic dyes, but the broad emission features in roughly the same spectral range for the red dyes along with the complication of the self-absorption effects [27] and fluorescence of the binding media and substrates makes the technique less effective [31].…”

Section: Multiple Pigmentsmentioning

confidence: 99%

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A holistic multimodal approach to the non-invasive analysis of watercolour paintings

et al. 2015

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A holistic approach using non-invasive multimodal imaging and spectroscopic techniques to study the materials (pigments, drawing materials and paper) and painting techniques of watercolour paintings is presented. The non-invasive imaging and spectroscopic techniques include VIS-NIR reflectance spectroscopy and multispectral imaging, micro-Raman spectroscopy, X-ray fluorescence spectroscopy (XRF) and optical coherence tomography (OCT). The three spectroscopic techniques complement each other in pigment identification. Multispectral imaging (near-infrared bands), OCT and microRaman complement each other in the visualisation and identification of the drawing material. OCT probes the micro-structure and light scattering properties of the substrate, while XRF detects the elemental composition that indicates the sizing methods and the filler content. The multiple techniques were applied in a study of forty-six nineteenth-century Chinese export watercolours from the Victoria and Albert Museum (V&A) and the Royal Horticultural Society (RHS) to examine to what extent the noninvasive analysis techniques employed complement each other and how much useful information about the paintings can be extracted to address art conservation and history questions. A micro-destructive technique of micro-fade spectrometry was used to assess the vulnerability of the paintings to light exposure. Most of the paint and paper substrates were found to be more stable than ISO Blue Wool 3. The palette was found to be composed of mostly traditional Chinese pigments. While the synthetic pigment, Prussian blue, made in Europe, was found on some of the paintings, none was found on the RHS paintings accurately recorded as being between 1817 and 1831 even though it is known that Prussian blue was imported to China during this period. The scale insect dyes, lac and cochineal, were detected on nearly every painting including those that fall within the identified date range. Cochineal is known to have been imported to China in the same period. While carbonbased ink was used for the drawings in the V&A paintings, graphite pencil was used in most of the RHS paintings. The majority of RHS paintings were on Western papers, but nearly all of the V&A paintings were on Chinese papers. Nearly all of the V&A painting substrates and hardly any of the RHS paintings were sized with alum. Elements such as Cu, Zn, Ti and Pb were detected on nearly all of the RHS papers regardless of whether they were Chinese or Western papers. These elements were largely absent from the V&A papers. The differences between the two collections reflect their discrete origins and intended purposes.

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Section: Multiple Pigmentsmentioning

confidence: 99%

“…Confirmation of the identification of lac and cochineal can be obtained in the future by surface enhanced Raman spectroscopy [38][39]. The technique is micro-invasive as it would require removing at least a fibre from the painting.…”

Section: Multiple Pigmentsmentioning

confidence: 99%