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Exposure of heritage plastics to solvents can cause several changes to their surface layers and bulk. The amorphous nature of certain plastics, particularly polymethyl methacrylate (PMMA), allows penetration and diffusion of low-molecular liquids, which can lead to swelling, cracking, plasticisation or stiffening, extraction and dissolution of polymer and additive components. Such phenomena compromise the visual characteristics, chemical and physical structure of heritage collections and remain, for the most part, unexplored. Research studies present contradicting evidence concerning the use of solvents and their safe application on PMMA. The main discrepancy is about PMMA being permeable to water or not. Alcohols have also triggered debates about whether they cause leaching and/or depolymerisation. This paper investigates the potential effects that selected free polar and non-polar solvents—employed in different media as cleaning systems—can have on PMMA after prolonged contact. The Hildebrand solubility theory was used to select solvents based on PMMA’s miscibility. The effects of deionised water, ethanol, isopropanol and petroleum ether are examined through a 30-day immersion study of PMMA via microscopic examination, weight change measurements, ATR-FTIR, peak height ratios, and NMR MOUSE. All four solvents extracted soluble components, i.e. unreacted residual monomer, and increased PMMA’s surface sensitivity to abrasions. Water and petroleum ether did not cause any measurable chemical or physical changes. Alcohols caused surface crystallisation and crazing, with isopropanol leading to stiffening and ethanol to plasticisation of the material. These effects, although extreme and absent in most routine cleaning timeframes, demonstrate the cumulative damage these solvents can potentially induce to PMMA.

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Training and education paths in conservation science have been the subject of ongoing debate over the last two decades. A key issue is that conservation science, although not a new field, is not adequately defined, which leads to a lack of consensus regarding the competencies needed. During the ICCROM Forum 2013 on Conservation Science, education for conservation scientists was discussed, with a particular focus on those necessary competencies which exceed the scientific domain. This paper reflects on the outcomes of these discussions as well as the results of surveys carried out by ICCROM in preparation for the Forum on education, job advertisements, and the relationship between conservation professionals and science. Challenges identified included current professional paths, dissemination of scientific findings, use of specialized terminology, and the need for professionals who serve more than one area of specialization. These challenges could be viewed as an opportunity to revise and modify educational programmes. New interactive platforms could be used to facilitate participative science projects, and could change the way projects are carried out in the near future.

This paper discusses the use of solvent-gel systems for the cleaning of poly (methyl methacrylate) (PMMA) surfaces. Aqueous polymer gel systems have been introduced to the conservation field with a particular focus on paintings, painted surfaces of wooden artefacts and stone. However, their application on plastics is very recent. Statistically designed experiments aimed to assess the efficiency and damage potential of materials constituting selected solvent-gel cleaning systems. The effect of the free solvents (deionized water, ethanol, isopropanol and petroleum ether), the hydrogel carriers (Agar, Pemulen™ TR-2, Carbopol® EZ 2-Ethomeen® C-25 and 80% hydrolysed PVAc-borax) and their combinations after 5 and 60 minutes of application time on PMMA surfaces, were evaluated through qualitative visual microscopic observation and SEM imaging, and quantitative weight change measurements. Visual observations revealed that the action of solvents (i.e. ethanol and isopropanol) was moderated by gellation (i.e. Agar), while other gel systems (i.e. Pemulen) were unsatisfactory. Results of gravimetric studies showed that most solvent-gels resulted in inconsistencies and large weight changes.

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