Emilio Cano

Volatile emissions from materials used in conservation have the potential to damage cultural assets when in contact with them or when accumulated in enclosed spaces. To evaluate material’s emissions and their potential interaction with museum collections, the Oddy test remains widely used by cultural institutions as an accelerated corrosion test. However, it presents several limitations related to its duration, the limited reactivity of its metal substrate and the degree of subjectivity involved in interpreting results.,In this study, trap-enrichment Solid-Phase Microextraction Gas-Chromatography Mass-Spectrometry (trap-enrichment SPME-GC-MS) was applied to analyze the volatile emission of nine Fused Deposition Modeling (FDM) polylactic acid (PLA) materials previously tested with the Oddy test. The main aim was to gain a deeper understanding of the potential long-term volatiles emitted by FDM materials and their relationship with the corrosion products formed during the Oddy test, analyzed by Raman spectroscopy.,Prior to the analysis, the method was optimized and validated using three FDM materials. A sample mass of 1 g was found to be suitable for characterizing the emission profile while maintaining reproducible results. The operating temperature during the sampling played a significant role by increasing the number of released compounds while not exceeding 80 ºC.,Finally, volatile emissions were correlated with the Oddy test results. In addition, Raman spectroscopy measurements were taken on the corrosion products formed on the Oddy test coupons. Results show that headspace analysis provides a more detailed chemical insight than the Oddy test. The optimized headspace method presented in this study can be applied to other materials to obtain information about their composition and emission. However, volatile studies demand a higher level of expertise for proper data interpretation.

Silver tarnishing in museum environments depends on multiple, interacting factors that are not often studied in situ. With the aim of addressing the problem in real-world scenarios, this study presents a one-year assessment at the National Archaeological Museum of Spain, in Madrid, a museum that houses a significant collection of silver objects. Pure Ag coupons were placed in four display cases—two designs with different airtightness—and in an adjacent gallery. Tarnishing was quantified by colorimetry, gravimetry, and galvanostatic reduction, and analyzed in relation to environmental parameters (T/RH) and gaseous pollutants (H₂S, SO₂, HF, HCl, formic and acetic acids), measured with passive samplers. Coupons showed different degrees of tarnish, with annual corrosion rates ranging from IC1 (very low) to IC2 (low), without a straightforward relation to hydrogen sulfide concentrations. Electrochemical profiles and XPS on representative coupons identified Ag₂S as the dominant product, with AgCl and minor Ag₂SO₄ in the coupons exposed outside the airtight cases, indicating different contributions inside and outside the cases. Findings highlight that sulfide concentration is not the sole driver; case airtightness, internal materials, cleaning products used on adjacent areas, and, possibly, other aspects influence silver tarnishing.

Materials such as wood, textiles, or plastics that are part of the exhibition system in museums are known to emit pollutants such as organic acids. Scientific and technical objects that include these materials in their composition can themselves be a potential source of emissions, which, together with inappropriate humidity and temperature conditions, can lead to corrosion of the metallic parts. In this work, we have studied the corrosivity of different locations in two venues of the Spanish National Museum of Science and Technology (MUNCYT). Coupons of the most representative metals from the collection were placed in different showcases and rooms for 9 months. The corrosion of the coupons has been evaluated in terms of the rate of mass gain, colour changes and characterisation of the corrosion products. The results were correlated to the relative humidity and concentration of gaseous pollutants to determine which metals are most susceptible to corrosion. The results show that metal artefacts exposed in showcases have a higher risk of corrosion than those exposed directly in the room, and that some pollutants are emitted by the artefacts. The corrosivity of the museum environment is low for copper, brass, and aluminium in most locations; however, some placements present a higher aggressivity for steel and lead, due to the high humidity and the presence of organic acids.

This paper presents results on the protective properties of different coatings over metals representative of those found in scientific–technical heritage collections. An examination of several objects in the collection of the Spanish National Museum of Science and Technology have allowed the identification of brass and steel as the most representative metals, and the existence of coatings (mainly shellac and acrylic resins) applied for aesthetic and/or conservation purposes. Based on these findings, brass and steel coupons coated with Paraloid B-44, B-48, B-67, B-72, Incralac, Cosmolloid H80, B-72 + H80 double layer and shellac have been studied to carry out a first screening in order to select the most promising candidates and determine the most appropriate methodology and key factors for the study. Coatings have been aged up to 336 h using cycles of UV light and water condensation. The change in the aspect of the coupons has been assessed via visual examination, optical microscopy and colorimetric measurements, with B-44 and Incralac showing the least change. EIS has been used for a quantitative evaluation of the protective properties and FTIR to measure chemical changes experienced by some coatings, such as B-48 and B-67. These evaluations allowed us to follow, understand and compare the behaviour of the different coatings and substrates after artificial ageing.