A method has been developed for identification of corrosive iron-gall inks in historical drawings and documents. The method is based on target-factor analysis of visible-near infrared fibre optic reflection spectra (VIS-NIR FORS). A set of reference spectra was obtained from model samples of laboratory-prepared inks covering a wide range of mixing ratios of basic ink components deposited on substrates and artificially aged. As criteria for correspondence of a studied spectrum with a reference spectrum, the apparent error in target (AET) and the empirical function SPOIL according to Malinowski were used. The capability of the proposed tool to distinguish corrosive iron-gall inks from bistre and sepia inks was evaluated by use of a set of control samples of bistre, sepia, and iron-gall inks. Examples are presented of analysis of historical drawings from the 15th and 16th centuries and written documents from the 19th century. The results of analysis based on the tool were confirmed by XRF analysis and colorimetric spot analysis.
A high-energy capacitor bank (2 × 1 µF/20 kV in a Blumlein circuit) was discharged over about 3 µs through a 7 mm electrode gap in water suspensions of different materials-TiO 2 powder, wood materials (sawdust, needles)-and methylhydroxyethylcellulose dissolved in water. The Mach number of the compressional wave produced by the expanding discharge channel achieved a value of about 0.5. The destruction of added materials was tested using various methods: turbidity and covering ability of the TiO 2 -white, acid hydrolysis of beech sawdust, microbiological processes of spruce needles and molecular weight measurements of the cellulose derivative. In the used power conditions the physical destruction of materials dispersed in water (degassing and decomposition of physically bonded particles) is a dominant effect caused mainly by the compressional wave that can affect material in the whole volume. The chemical destruction probably occurs just in the vicinity or inside the plasma channel due to the action of plasma particles or energetic radiation.
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