Analysis of red chalk drawings from the workshop of Giovanni Battista Piranesi using fiber optics reflectance spectroscopy

The viability of fiber optics reflectance spectroscopy (FORS) for the differentiation of red chalk drawing media was investigated, focusing on the group of drawings from the workshop of Giovanni Battista Piranesi (1720–1778) at the Staatliche Kunsthalle Karlsruhe, Germany. The evaluation of spectra was supported by principal component analysis (PCA). The method was tested on mock-up drawings made with recently acquired natural and synthetic red chalks of known origin. It was possible to sort these mock-up drawings according to chalk type and application technique. The compositional differences of these reference chalks were confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Subsequent FORS analysis of selected original drawings revealed the existence of several closely grouped clusters, implying similarities on the basis of the underlying spectral features among the historical red chalks used in Rome. These similarities distinguished the historical drawings from the red chalk mock-up drawings, except for the drawings made with red chalk samples from the area near the town of Theley, Germany, which were shown to bear close similarities to those in the cluster of historical samples

Gellan residues on paper: quantification and implication for paper conservation

Abstract Gels prepared from the polysaccharide gellan are used for aqueous poulticing treatments in paper conservation when the application of water must be restricted. Optimal use of the rigid, yet shapeable gel requires direct contact with the paper surface, which carries the risk of gel residues on the treated surface. We used acid methanolysis as a destructive analytical method to detect rhamnose as a component of gellan, which was undetectable with ATR-FTIR spectroscopy. We show that there is a significant probability of leaving gellan residues on the paper. Conservators should be aware of this potential side effect when considering the use of gellan poultices in direct contact with paper objects

Dissolution Behavior of Different Celluloses

Celluloses from different origins were dissolved stepwise in N,N-dimethylacetamide/lithium chloride (9% v/w; DMAc/LiCl) with the aim to study the time course of the dissolution process, Completeness of dissolution in the dissolved fractions, possible discrimination effects, and differences between the celluloses. Cellulosic pulps from both annual plants and different wood species were analyzed. The obtained fractions were subject to gel permeation chromatography (GPC) with multiple detection to monitor the development of molecular mass distribution (MMD), molecular mass, and recovered mass. The dissolution behavior of accompanying xylans was followed by quantitative analysis of the uronic acids by fluorescence. labeling - GPC. The morphological changes at the remaining fibers in the stepwise dissolution were addressed by SEM. The time needed to dissolve completely the cellulosic pulp differed from species to species, mainly, between pulps from annual plants and pulps from wood. Annual plants generally needed much longer to dissolve completely. In the beginning of the dissolution, the dissolved fractions of annual plants showed a distinct discrimination effect because they were enriched in hemicellulose. By contrast, wood pulps dissolve fast and without distinct changes in the MMD of the dissolved fractions over time. Bagasse pulp is an exception the observation for annual plants and rather resembled the behavior of wood celluloses. Prolonged dissolution times, as often practiced in Cellulose GPC, do not lead to any improvements regarding the determination of molecular mass, MMD, and recovered, Mass of injected sample, so that the dissolution times required for reliable GPC analysis can be significantly shortened, which will he important for biorefinery analytics with high numbers of sample

Electron Beam Irradiation of Cellulosic Materials—Opportunities and Limitations

The irradiation of pulp is of interest from different perspectives. Mainly it is required when a modification of cellulose is needed. Irradiation could bring many advantages, such as chemical savings and, therefore, cost savings and a reduction in environmental pollutants. In this account, pulp and dissociated celluloses were analyzed before and after irradiation by electron beaming. The focus of the analysis was the oxidation of hydroxyl groups to carbonyl and carboxyl groups in pulp and the degradation of cellulose causing a decrease in molar mass. For that purpose, the samples were labeled with a selective fluorescence marker and analyzed by gel permeation chromatography (GPC) coupled with multi-angle laser light scattering (MALLS), refractive index (RI), and fluorescence detectors. Degradation of the analyzed substrates was the predominant result of the irradiation; however, in the microcrystalline samples, oxidized cellulose functionalities were introduced along the cellulose chain, making this substrate suitable for further chemical modification

Etherification of Wood-Based Hemicelluloses for Interfacial Activity

We present wetting, hygroscopicity, and interfacial activity of hemicellulose with respect to etherification and contrast it to their potential as interfacial modifiers, which is demonstrated by oil-in-water emulsification containing up to 60 vol% of the oil phase. Tunable amphiphilicity of hardwood and softwood hemicelluloses, xylans, and galactoglucomannans, respectively, was accomplished via controlled etherification. A series of degree of substitution (DS) of hydroxypropylated and 3-butoxy-2-hydroxypropylated ("butylated") grades was synthesized. The hemicellulose ethers were characterized by gel permeation chromatography, spectroscopic techniques, such as NMR, and contact angle measurements. An attenuated total reflectance infrared method was developed for fast identification of the DS. Near infrared analysis was utilized to explore the hygroscopicity of the material and to perform principle component analysis. The modification to butylated grades decreased the hygroscopicity, whereas the hydroxypropylated grades bound moisture. All of the hemicellulose ethers were water-soluble. The interfacial tension of the aqueous hemicellulose solutions was determined by pendant-drop tensiometer, and it was demonstrated to be dependent on the degree of modification