Heritage Science Laboratory Ljubljana

Tomaž Mržljak

Historic artifacts are a vital part of our cultural heritage, so they need to be protected from substances that could harm them – the ones in museums are particularly endangered, especially if the buildings are not (well-)ventilated. The project focuses on characterization of sorbents that could be suitable for the protection of artifacts by absorbing harmful compounds, which would otherwise degrade (decompose) them. First, a general test of sorbents is done with the Oddy test, where we can superficially assess whether the sorbent is suitable to be placed near the artifacts, as it could also emit harmful compounds. Sorbent analysis is continued by SPME sampling. Identification of the resulting compounds is done by GC / MS.

Supervisor: Irena Kralj Cigić

David Ribar

The work focuses on the development of a model for reversed-phase chromatographic separations based solely on thermodynamic parameters and minimal experimental retention data. The parameters used in the model include Hansen solubility parameters and analyte molar volumes, both of which are estimated using various theoretical calculations. Initially, the experimental investigation of retention processes of selected phthalates will be carried out. This will be followed by the development of a theoretical model that enables the prediction of retention factors for the larger group of analytes under investigation.

Phthalates are a key component in many polymeric heritage materials and serve as plasticizers. Often, they do not mix well with the base polymer and may migrate out of the polymer matrix under various environmental conditions, and form surface deposits, contribute to changes in the specific volume of the material and thus promote cracking and loss of mechanical properties. The study will contribute to our understanding of the solubility of phthalates in polymeric matrices.

Supervisors: Irena Kralj Cigić and Matija Strlič

Daša Terobšič

Various metals originating from catalyst residues, stabilizers and some additives such as flame retardants, antimicrobial reagents, plasticizers and pigments can be found in synthetic fibers and plastic materials of everyday use. Excessive concentrations of these metals can adversely affect the properties of such materials, so the quantitative determination of metals is important for the identification of impurities, for the assessment of the quality of polymer production, and also from the point of view of understanding the effect of metals on the durability of the material. In the case of poly(vinyl chloride), during the decomposition of the polymer, organometallic compounds, metal oxides or carbonates, which are added as stabilizers, react with the resulting hydrochloric acid, which is eliminated from the polymer chain, and thus prevent decomposition. In my master’s research, I optimized the microwave decomposition of PVC and subsequently determined the metals in the resulting solution using ICP-OES. I checked the results for some samples using SEM-EDS. The goal of the master’s research is primarily to find meaningful connections between the presence of various metals and the properties of PVC and to determine how these metals affect the durability of the material.

Ana Šiško

Copper-based green pigments promote the deterioration of many valuable historical manuscripts. Verdigris was often used, from antiquity to the 19th century, as a green or green-blue pigment. Despite the fact that it is very unstable, as the color changes with time and depending on atmospheric conditions, it was widely used for manual coloring of printed material, as it is semi-transparent and does not cover the printing ink. It was mainly used on illuminations, book illustrations and maps.

The aim of the project is to study the degradation of different papers with the application of verdigris pigment under the conditions of thermal accelerated degradation, which is comparable to the natural degradation. Model samples will be analysed by AAS, SEC, FTIR and colorimetry. The influence of two antioxidants on the stability of verdigris paper will also be evaluated under the same conditions and with the same methods. Part of the samples will be treated with tetrabutylammonium bromide, which has an antioxidant effect in the pseudo-Fenton reaction system on verdigris paper. The second part will be treated with 1H-benzotriazole (BTA), which has also been shown to slow down the degradation of verdigris paper, but the research was conducted under thermally accelerated degradation conditions that are not comparable to natural pigment degradation processes.