Damage function for historic paper. Part III: Isochrones and demography of collections

Background: In the context of evidence-based management of historic collections, a damage function combines aspects of material degradation, use, and consideration of material attributes that are important for satisfactory extraction of benefits from user interaction with heritage. In libraries and archives, it has been shown that users (readers and visitors) are mainly concerned with loss of textual information, which could lead to degradation being described as unacceptable, at which an object might become unfit for use and therefore damaged. The contribution explores the development of the damage function for historic paper based on data available in the literature. Results: We have modelled the dose–response function taking into account 121 paper degradation experiments with known T, RH of the environment, and pH of paper. The function is based on the Arrhenius equation and published water absorption isotherm functions for paper. New isoperm plots have been calculated and isochrones have been developed. These are plots linking points of equal expected ‘lifetime’, i.e. time until an object is expected to reach the state of threshold fitness-for-use. We also modelled demographic curves for a well-characterised research collection of historic papers, exploring the loss of fitness for use with time. Conclusions: The new tools enable us to evaluate scenarios of management of the storage environment as well as levels of access, for different types of library and archival paper. In addition, the costs and benefits of conservation interventions can be evaluated. The limitations of the function are the context of use (dark storage and reading), exclusive focus on the properties of an average paper type, and de-prioritised effect of pollutants; however, the latter can be considered separately. This work also demonstrates that transparent and publically accountable collection management decisions can be informed, and challenged by, effective interaction with a variety of stakeholders including the lay public

Effects of NO2 and acetic acid on the stability of historic paper

This research investigates degradation of historic paper in polluted environments during long-term dark storage. In an innovative experiment, degradation rates at realistic pollution levels are compared with degradation rates in the absence of pollution, using a set of real historic papers. The most abundant pollutants in repositories in post-industrial environments are taken into account: acetic acid and nitrogen dioxide. Their action was assessed in terms of reduction of ‘handling’ (as defined by decrease in degree of polymerisation) and ‘display’ (as defined by discolouration) lifetimes. Extrapolations to room conditions enabled lifetime predictions in conditions that are comparable to a real archival or library repository environments while prediction uncertainties were analytically evaluated to assess the significance of conclusions. While 10 ppb of NO2 does reduce the handling lifetime of almost all types of paper, their predicted lifetimes were still assessed to be several millennia, with the exception of acidic paper. Acetic acid at concentrations that are typical for archival and library repositories (<100 ppb) has significantly less effect than NO2 while it does not affect display lifetimes. From a conservation management perspective, it needs to be addressed whether the predicted reductions in otherwise significant handling lifetimes are of real concern and whether air filtration in archival and library repositories is justified

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals &lt;1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Easy-to-use, low-cost electrochemical open-source hardware to analyse heritage metals: Possibilities and limits

Open-source hardware (OSHW), as low-cost and easy-to-use instrumentations, are particularly suited to the needs of the conservation field. This paper presents two OSHWs developed for the diagnosis of heritage metal artefacts. The DiscoveryMat application allows the qualitative analysis of slightly oxidised metals such as copper and aluminium-based alloys, through the standardized monitoring of the variation of their corrosion potential (Ecorr) with time. The Pleco allows the local identification of corrosion products through linear sweep voltammetry (LSV) plots and this contributes to a better adjustment of conservation treatments on metal artefacts covered with heterogeneous corrosion layers through the selective intervention on some corrosion products and the preservation of others. If the Pleco can already be found in the toolbox of some conservation professionals, the DiscoveryMat application is still in its infancy and needs to be developed in the future as a participatory tool

Silver particle-decorated carbon paste electrode based on ionic liquid for improved determination of nitrite

A simple silver particle-modified carbon paste electrode is proposed for the determination of low concentration levels of nitrite ions. The electrode consists of a carbon powder decorated with silver sub-micrometre particles (AgPs) and a hydrophobic ionic liquid trihexyltetradecylphosphonium chloride as a binder. It has been shown that AgPs exhibit a strong electrocatalytic effect on the nitrite oxidation. For optimal electroanalytical performance the electrode was conditioned via silver oxidation/reduction cycle. The electrode revealed a linear square-wave voltammetric response in a wide examined concentration range of 0.05 to 1.0 mmol L−1, limit of detection (LOD) of 3 μmol L−1 and excellent repeatability with RSD of 0.3%. Keywords: Silver particles, Square-wave voltammetry, Nitrite, Ionic liquid, Carbon paste electrod

Exploring suitable parameters for electrochemical cleaning/consolidation of museum objects and practical use of the Pleco electrolytic pencil

In the past, many objects in the collection of the National Museum of Slovenia were severely damaged due to electrolytic/electrochemical cleaning. In the early 1990s, the decision was made to abandon this kind of treatment due to its harshness, although at the time important developments in electrolytic/electrochemical cleaning were underway in Europe that used stricter control parameters such as cathodic potentials determined by voltammetry