The protection of silver collections from tarnishing

Abstract

An integrated project with the objective of reducing the tarnishing of silver in muse.um collections has three research components: (I) to develop, validate and deploy passive samplers for the quantification of the relevant pollutant gases (hydrogen sulphide, H 2 S, and carbonyl sulphide, OCS); (2) to identify and evaluate suitable transparent polymer systems which can provide effective sealed pouches for storage of silver;(3) to synthesize, characterize and test new absorbents to remove these pollutant gases from showcases. Passive samplers for H2S and OCS gases have been developed and both have undergone laboratory validation. The passive sampler for H2S has been deployed in four museums in The Netherlands; the H2S concentrations span the range 0-1000 parts per trillion and show considerable variation depending on the season and the site. A standard method has been developed for the preparation of silver test coupons for assessing the development of silver tarnish in laboratory experiments and in museum display cases. Novel absorbents have been synthesized, characterized and tested for their efficacy in removing H2S pollution from museum showcases. The absorbents were considerably more effective at H2S removal than commercial absorbents tested under the same laboratory conditions. A range of commercial polymer films has been selected, on the basis of their specified low permeability to oxygen, for evaluation as H2S barriers, and preliminary laboratory permeability studies have been carried out.

Pollution and Heritage Metals—Effectiveness of Oddy Testing and Mitigation

“…Colorimetry All Issues with early stages of Pb corrosion [23][24][25] X-ray photoelectron spectroscopy Ag [26,27] Static Secondary ion mass spectrometry Ag [27] Dynamic Secondary ion mass spectrometry Ag [27] Oxygen depletion Cu, Pb, (Fe) Measurements of the test atmosphere and not the metal coupons [28] All the techniques listed have proved to be able to quantify corrosion, at least on some coupon types. The corrosion layers on silver are often very thin and require sensitive techniques to detect them.…”

Monitoring pollutant gases in museum microclimates: a relevant preventive conservation strategy

“…A prata sofre corrosão quando exposta a H2S em concentrações da ordem dos µg m -3 [29,51]. Adicionalmente, estudos [51] mostraram que o sulfureto de carbonilo (COS) contribui para o escurecimento da prata e pode ser, em alguns casos, o principal agente deste escurecimento. Elevadas concentrações de O3 e NO2, em ambientes com elevada HR, tendem a contribuir com a formação de óxidos e hidróxidos na prata [52].…”

Monitoring the impact of the indoor air quality on silver cultural heritage objects using passive and continuous corrosion rate assessments

“…Conventionally, coulombic reduction is used [9,13]. The change in visual appearance has also been used as a way to determine the corrosion extent [14]. Furthermore, resistance measurements of nm-thick metal wires can monitor metal loss over time (e.g., Cosasco®, AirCorr®) [15][16][17][18].…”