Pigments. The investigation of the effect of organic pollutants on pigments was carried out on model samples at Ghent University (Belgium) by means of non-destructive techniques. Five pigments were selected for in depth investigation: lead white, red lead, lead tin yellow type I, malachite and sunfast orange (PO36). Experiments were carried out with no binder medium and no varnish layer, representing a worst case scenario. Both the binder medium and varnish would be expected to protect the pigment. Periodical investigation of pigments samples exposed to organic pollutants (different concentrations of acetic acid in the atmosphere, different length of exposure) was carried out with different techniques, as digital imaging and vibrational (Raman) spectroscopy, to evaluate both the on-going visual changes and molecular modifications. It is important to point out the availability of mobile/portable Raman instruments: in situ measurements are becoming more and more exploitable for the survey and monitoring of works of art inside their environment. On exposure to acetic acid in the range ca. 280 mg m3*days - 142000 mg m3*days (1 week of exposure to 1% acetic acid at 75% RH and 7 weeks of exposure to 100% acetic acid at 75% RH, respectively), colour changes were observed for all pigments, but no specific trend could be defined. For the three lead based pigments, lead acetate was detected by means of Raman spectroscopy as the expected degradation product. The combined effect of the concentration of acetic acid in the atmosphere and the length of the exposure is expressed through the dose. The relative intensity of the degradation product (i.e. the ratio between the Raman intensity of the degradation product band versus the Raman intensity of one characteristic band of the intact pigment) was then correlated with the acetic acid dose responsible for that change, as in Figure 10 for lead tin yellow type I. Alteration is likely to occur for doses above 4250 mg m3*days (lowest observable adverse effect limit, LOAEL), while up to a dose of ca. 3400 mg m3*days no changes in the sample can be detected: it means that the environment can be considered safe for that specific pigment. This latter value corresponds to NOAEL (no observable adverse effect limit) and is set at 20% lower values than LOAEL. Between these two values, the environment can be potentially harmful. The change in air quality is reflected in the formation of the expected degradation product. For red lead and lead w...
Pigments. Two different pigments were used to create red paint: iron oxide, also known as red ochre, and cinnabar. Both have vastly different sources and applications, but are indistinguishable to the naked eye. It is necessary to use methods such as microscopic analysis in order to differentiate the two different pigment makeups. The surviving traces on the figurines depict ornamentation like jewelry, anatomic features like eyes and hair, and more symbolic motifs such as zigzags. The focus of this section is not to examine the meaning of the decorations, which works towards a narrative subject, but to seek the embodied experience and value of the pigments themselves: where they came from and how they were used. Iron oxide is more widely available (with regards to extraction) in the Cyclades. There were sources are as near as Kea in the northwest Cyclades.111 Iron oxide, however, was not as commonly used on the figurines as cinnabar, which is an exotic pigment in the Cycladic islands. Some identified ancient sources of the pigment coming from as far as Spain and the Colchis near the Black Sea as well as in Asia Minor.112 Xxxxxxx lists some local sources for cinnabar, but deems them not “commercially viable.”113 These sources include Naxos, Chios, Samos, and Euboea; she judges the quantities of cinnabar deposits found in these locations to be too small to have been used reliably.114 It is not clear what it meant by too small quantities, but it does suggest a question about how much of the pigment was being moved. Use of cinnabar is attested in the Aegean as early as the Late Neolithic.115 Cinnabar provides a brighter and deeper red than 111 Xxxxxx (2008) 121. 112 Pandermalis (2012) 22-23. 113 Xxxxxxx (2003) 428 fn. 70. 114 Xxxxxx (2008) 122. 115 Birtacha “Examining the Paint on Cycladic Figurines,” in Marthari, Xxxxxxx, and Xxxx (2017) 495; she cites an unpublished example of a marble acrolithic figurine from Dimini painted with cinnabar from Topa and Xxxxxxx in press. iron oxide. A fresh coat of cinnabar paint might have been recognizable from the red ochre/iron oxide on the marble figurines. Does this entail that figurines with cinnabar paint were more valuable or coveted than their counterparts? If cinnabar was both rare to acquire and provided a deeper red, then a crafter who had access to this pigment may have used it to create higher value in the body he crafted through his own physical exertions or social connections to those who traversed those routes, as wel...
Pigments. 1.5.1 Yellow and re-ochre - The Ochres shall conform to I.S. 47 - 1970. The solid lump shall be crushed to power.
Pigments. 1.3.1 White: Sufficient titanium dioxide pigment will be used to ensure a color equivalent to Federal Highway White, Docket No. FHWA-99-6190 Table 5 and Table 6 as revised and corrected. xxxx://xxxxx.xxxx.xxx.xxx/kno-colorspec.htm.
Pigments organic or inorganic pigments or opacifying agents (colour or transparent) • pigments in any form—including — granulars — dry powders — pastes — dispersions — suspensions
