An evaluation of irganox 565 as a stabilizer for dammar picture varnishesde la Rie, E. René
doi: 10.1179/sic.1988.33.3.109pmid: N/A
AbstractChanges during the aging of dammar resin films containing the antioxidant Irganox 565 were observed using ultraviolet-visible light transmission spectrophotometry and solubility tests. The concentration of the stabilizer was monitored with the aid of high performance liquid chromatography. Although the additive stabilizes dammar during heat aging in the dark, it breaks down rapidly during fadeometer aging and during natural aging behind a window facing south. Furthermore, colored degradation products of Irganox 565 cause increased yellowing during combined fadeometer-heat aging. In view of the fact that light plays an important role in the autoxidation of dammar, Irganox 565 is not recommended as a stabilizer for dammar varnishes.
Technical examination and restoration of a ceremonial shield from the Solomon IslandsKenndler, E.; Mairinger, F.; Bauer, W. P.; Rainer, F.; Schmidt-Beiwl, K.
doi: 10.1179/sic.1988.33.3.115pmid: N/A
AbstractThe materials of a shell-inlaid shield (wicker, paste layer and mother-of-pearl) were subjected to a technical examination. The wicker and the mother-of-pearl were examined by microscopy and the materials used were identified by visual comparison with appropriate reference materials. The paste layer was analyzed using microchemical methods. The fatty acid analysis of the oleaginous binding medium of the paste layer was carried out by gas chromatography and mass spectrometry. The fatty acid composition of a tropical nut (Parinarium hahlii Warb.), potentially used as binding medium, was investigated. The main component was identified as the highly unsaturated elaeostearic acid (9, 11,13-octadecatrienoic acid). For reference purposes, the pulp material of the kernels of the parinarium nut was artificially aged. The resulting gas chromatographic pattern was found to correspond qualitatively with that of the paste layer, supporting the assumption that parinarium nuts were applied as the binding media for such shields. The consolidation of the shield was carried out using a stabilizing emulsion, which was specially developed for this purpose. The restoration of the shield is described in detail, especially the replacement of 262 shell chips.
A support system for a wall frieze from Teotihuacán, MexicoBone, Lesley
doi: 10.1179/sic.1988.33.3.126pmid: N/A
AbstractThe paper describes the conservation and construction of a support system for 15 frescoed wall fragments that depict a feathered serpent with a border of flowering trees. A support system was designed and manufactured to meet the following requirements: the mounting system was to be as discreet as possible, providing adequate support and preserving the integrity of the mural including the backing; it had to work for display and in storage; the solution had to permit maximum access to the front, back and sides of the murals for any subsequent scientific or historical examination.
Relative humidity and the stress/strain response of canvas paintings: uniaxial measurements of naturally aged samplesHedley, Gerry
doi: 10.1179/sic.1988.33.3.133pmid: N/A
AbstractFive naturally aged painting fragments and primed canvas samples from dates between c. 1825–1912 were examined to determine their mechanical behaviour during RH cycling. The tests were performed mostly at room temperature and the samples were tested uniaxially. All of the samples showed the same basic response pattern. Below a relative humidity of about 80% restrained specimens gained tension during desorption and lost tension during absorption. Above 80% RH the opposite occurred, to a greater or lesser degree, depending on the shrinkage tendency of the fabric support. The form of the recorded response curves matched that predicted by Mecklenburg who superimposed the behaviour of individual layers so as to model whole painting response. Free-hanging specimens contracted in conditions when the restrained specimens gained tension and enlarged when they lost tension. Shrinkage movements as large as 1% were recorded for some samples at 98% RH. Beeswax impregnation was found to suppress the tension variation of a sample exposed to RH cycling. An old glue/paste lining on one of the samples was reformed by exposure to high RH resulting in increased tension values in dry conditions.
Multispectral image processing of paintingsAldrovandi, A.; Bertani, D.; Cetica, M.; Matteini, M.; Moles, A.; Poggi, P.; Tiano, P.
doi: 10.1179/sic.1988.33.3.154pmid: N/A
AbstractA reflectographic apparatus, equipped with an image processor, has been used to obtain a trichromatic image of paintings comprehensive of both visible and infrared (700–1000nm) regions. The first step has been to reproduce with MIPP (multispectral image processing of paintings) images similar to those obtained with IR Kodak colour film. A good discrimination of both pigments and overpainting is possible with this technique which operates in a more flexible and powerful way than IR ‘false colour’ photography. Results are shown relative to a test panel and a tempera painting with extensive overpaint. The possibility of utilizing this technique to correlate a single pigment with its MIPP image is now under investigation.