Preservation Of Cultural Heritage Materials Research Articles

Hydrophobic and Photocatalytic Treatment for the Conservation of Painted Lecce stone in Outdoor Conditions: A New Cleaning Approach

Self-cleaning and hydrophobic treatments based on TiO2 and SiO2 nanoparticles are widely applied for the preservation of cultural heritage materials, to improve their resilience in polluted environments. Excellent results have been obtained on stone materials, but experiments on painted stone surfaces, such as wall paintings and polychrome plasters used in historic buildings, are still limited. In this work, we present a study on the use of water dispersions of TiO2 nanoparticles obtained via sol-gel and organically modified silica (OrMoSil) for cleaning and protective purposes on Lecce stone, a carbonate stone, widely used for its excellent workability but easily attacked by atmospheric agents and pollutants. First, we evaluated the harmlessness of the treatment on Lecce stone through colorimetric tests, water absorption by capillarity and permeability to water vapor. The photocatalytic activity of the TiO2 nanoparticles was assessed by photo-degradation of methyl orange and methylene blue dyes. The dispersion was then applied on painted samples prepared according to ancient recipes to confirm the effectiveness of the cleaning. The proposed TiO2/OrMoSil-based coating can act as a self-cleaning and protective treatment on lithic surfaces to prevent degradation phenomena and preserve the original appearance of the monument.

Preservation of Cultural Heritage Materials at the University of Witwatersrand

This study assessed the preservation of cultural heritage materials in selected universities in South Africa with a view of recommending the best preservation method. Particularly, it examined the availability of a preservation policy at the University of Witwatersrand, the types and format of cultural heritage materials held by the University, the major preservation challenges facing the University and to make recommendations for the effective management and preservation of all materials held by the University. The study established that indeed there is a lack of a preservation policy and challenges with regards to the management of cultural heritage in South Africa.

Ultrasensitive Monitoring of Museum Airborne Pollutants Using a Silver Nanoparticle Sensor Array.

The preservation of cultural heritage materials requires extremely low concentration limits for indoor pollutants. This poses an unmet challenge for monitoring the artwork in museums and on exhibit, especially to do so in a cost-effective manner for a large number of locations. A novel type of colorimetric sensor array based on printed inks of 10 nm silver nanoparticles (AgNPs) with several different capping agents has been developed as an alternative to metal coupons or other passive sampling indicators traditionally used by conservators. The AgNP colorimetric sensor array, combined with digital imaging, offers ultrasensitive dosimetric identification of acidic and oxidizing gases and other air pollutants commonly found in a museum; the limits of detection are sub-ppb for 1 h exposures. For an array of AgNP inks with various capping agents, a unique and distinguishable color response pattern is observed for each specific analyte. Excellent discrimination among 11 gas pollutants over a wide range of concentrations was demonstrated using standard chemometric methods. The observed changes in color during pollutant exposure originate from the sintering of solid-state nanoparticles that leads to changes in the localized surface plasmon resonance. Such chemically induced sintering mechanism of nanoparticles paves the way for a new class of field-deployable solid-state optical sensor arrays. As an example, we have demonstrated the use of AgNP sensor arrays for the nondestructive analysis of acidic volatile emission from five types of printing paper, relevant for the conservation of cultural heritage objects, including ancient manuscripts and books.

How to Tell Ancient Signs Apart? Recognizing and Visualizing Maya Glyphs with CNNs

Thanks to the digital preservation of cultural heritage materials, multimedia tools (e.g., based on automatic visual processing) considerably ease the work of scholars in the humanities and help them to perform quantitative analysis of their data. In this context, this article assesses three different Convolutional Neural Network (CNN) architectures along with three learning approaches to train them for hieroglyph classification, which is a very challenging task due to the limited availability of segmented ancient Maya glyphs. More precisely, the first approach, the baseline, relies on pretrained networks as feature extractor. The second one investigates a transfer learning method by fine-tuning a pretrained network for our glyph classification task. The third approach considers directly training networks from scratch with our glyph data. The merits of three different network architectures are compared: a generic sequential model (i.e., LeNet), a sketch-specific sequential network (i.e., Sketch-a-Net), and the recent Residual Networks. The sketch-specific model trained from scratch outperforms other models and training strategies. Even for a challenging 150-class classification task, this model achieves 70.3% average accuracy and proves itself promising in case of a small amount of cultural heritage shape data. Furthermore, we visualize the discriminative parts of glyphs with the recent Grad-CAM method, and demonstrate that the discriminative parts learned by the model agree, in general, with the expert annotation of the glyph specificity (diagnostic features). Finally, as a step toward systematic evaluation of these visualizations, we conduct a perceptual crowdsourcing study. Specifically, we analyze the interpretability of the representations from Sketch-a-Net and ResNet-50. Overall, our article takes two important steps toward providing tools to scholars in the digital humanities: increased performance for automation and improved interpretability of algorithms.

Multispectral Imaging for Scientific Analysis and Preservation of Cultural Heritage Materials

Multispectral Imaging for Scientific Analysis and Preservation of Cultural Heritage Materials

Investigation of pigment degradation due to acetic acid vapours: Raman spectroscopic analysis

The preservation of moveable cultural heritage objects inside museums includes trying to keep these objects under the best conditions as possible. This is done, amongst others, by controlling the atmospheric conditions under which the objects are preserved: the amount of light, temperature and relative humidity, etc. should be carefully monitored in exhibitions as well as in storage rooms. However, other atmospheric components may as well be important for the optimal preservation of cultural heritage materials, such as acetic compounds derived from wood package. A study of the degradation of malachite, leadwhite, lead-tin yellow type I, red lead and pigment orange 36 is performed using Raman spectroscopy. The degradation of these pigments was analyzed after exposure to acetic acid vapours. Three different acetic acid concentrations in the atmosphere were tested: ca. 150 ppm, ca. 300 ppm and ca. 500 ppm. In all conditions, the relative humidity was kept constant at ca. 75 %. A possible colour change, which can go hand in hand with the degradation process, was evaluated by observing the change of the RGB values of the sample colour. Besides pigment orange 36, which showed to be unreactive towards the acid atmosphere, acetate species were generated for each pigment: malachite reacted towards a verdigris variety; red lead, leadwhite and lead-tin yellow degraded towards lead acetate. At high doses, red lead alters towards a black pigment, which is presumed to be plattnerite.

Advanced Spectral Imaging for Noninvasive Microanalysis of Cultural Heritage Materials: Review of Application to Documents in the U.S. Library of Congress

Hyperspectral imaging was originally developed for remote sensing and astronomical applications, but adaptations of this technology have been of great benefit to the preservation of cultural heritage. Developments in noninvasive analytical techniques have advanced the preservation of cultural heritage materials by enabling the identification and analysis of a range of materials, utilizing their unique spectral response to nondestructively determine chemical composition, and determining states of deterioration and change due to environmental conditions. When used as a tool for noninvasive characterization of cultural heritage, these spectral imaging systems allow the collection of chemical identification information about materials without sampling, which is a critical factor for cultural heritage materials. The United States Library of Congress has been developing the application of hyperspectral imaging to the preservation and analysis of cultural heritage materials as a powerful noncontact technique. It allows noninvasive characterization of materials, by identifying and characterizing colorants, inks, and substrates with narrow-band illumination to protect the object while also monitoring deterioration or changes due to exhibit and other environmental conditions. Contiguous illumination from the ultraviolet, visible, and infrared spectral regions allows the capture of lost, obscured, and deteriorated information. The resulting image cube allows greater capabilities for mapping and coordinating a range of complementary chemical and spectral analyses. The capabilities of this technique are illustrated by a review of results from analysis of the Waldseemüller World Map, the L'Enfant plan for Washington, D.C., and the first draft of the U.S. Declaration of Independence.

Cost Model for Digital Preservation: Cost of Digital Migration

The Danish Ministry of Culture has funded a project to set up a model for costing preservation of digital materials held by national cultural heritage institutions. The overall objective of the project was to increase cost effectiveness of digital preservation activities and to provide a basis for comparing and estimating future cost requirements for digital preservation. In this study we describe an activity-based costing methodology for digital preservation based on the Open Archice Information System (OAIS) Reference Model. Within this framework, which we denote the Cost Model for Digital Preservation (CMDP), the focus is on costing the functional entity Preservation Planning from the OAIS and digital migration activities. In order to estimate these costs we have identified cost-critical activities by analysing the functions in the OAIS model and the flows between them. The analysis has been supplemented with findings from the literature, and our own knowledge and experience. The identified cost-critical activities have subsequently been deconstructed into measurable components, cost dependencies have been examined, and the resulting equations expressed in a spreadsheet. Currently the model can calculate the cost of different migration scenarios for a series of preservation formats for text, images, sound, video, geodata, and spreadsheets. In order to verify the model it has been tested on cost data from two different migration projects at the Danish National Archives (DNA). The study found that the OAIS model provides a sound overall framework for the cost breakdown, but that some functions need additional detailing in order to cost activities accurately. Running the two sets of empirical data showed among other things that the model underestimates the cost of manpower-intensive migration projects, while it reinstates an often underestimated cost, which is the cost of developing migration software. The model has proven useful for estimating the costs of preservation planning and digital migrations. However, more work is needed to refine the existing equations and include the other functional entities of the OAIS model. Also the user-friendliness of the spreadsheet tool must be improved in future versions of the model. The CMDP is presently closing its second phase, where it has been extended to include the OAIS Functional Entity Ingest. This has also enabled us to adjust the theoretical model further, especially regarding the accuracy and precision of the model and in relation to the underlying parameters used in the equations, such as migration frequency and format complexity. Understanding the nature of digital preservation cost is prerequisite for increasing the overall efficiency, and achieving first quality for preservation of cultural heritage materials.

Non-Invasive Characterization for Long-Term Preservation of Cultural Heritage

ABSTRACTDevelopments in non-invasive analytical techniques advance the preservation of cultural heritage materials by identifying and analyzing substrates and media. Spectral imaging systems have been used as a tool for non-invasive characterization of cultural heritage, allowing the collection of chemical identification information about materials without sampling. The Library of Congress has been developing the application of hyperspectral imaging to the preservation and analysis of cultural heritage materials as a powerful, non-contact technique to allow non-invasive characterization of materials, by identifying and characterizing colorants, inks and substrates through their unique spectral response, monitoring deterioration or changes due to exhibit and other environmental conditions, and capturing lost and deteriorated information. The resulting image cube creates a new “digital cultural object” that is related to, but recognized as a distinct entity from the original. The range of data thisobjectcontains encourages multidisciplinary collaboration for the integration of preservation, societal and cultural information.

Novel sol–gel reversible thermochromic materials for environmental sensors

Anhydrous cobalt(II) chloride has been encapsulated in several inorganic sol–gel matrices with different solvent/water ratios. Sols were cast into cuvettes and hermetically closed. Such sol–gel materials were found to be sensitive to temperature in the 10–50 °C range showing a change of colour. General characterisation of the sensitive materials was made by immersion into a thermostatic water bath and recording of the corresponding visible spectra. The optical response consisted of a change in colour from light pink to deep blue as the temperature increases. These temperature detectors behave as sensors showing good optical sensitivity in the range mentioned above and reversibility for more than 30 cycles. The sensors response time is at about 15 min and their lifetime is 2 months at least. These sol–gel materials have been designed to be applied for preservation and conservation purposes. High temperatures and cyclical temperature changes can yield severe consequences for the correct preservation of cultural heritage materials (textiles, archaeological ceramics and other remains, metallic objects and statues, stained glass windows, etc.) both in museums and outdoors.

Steering Resources to Safe-Harbor Repositories: The Need for Reliable, Accurate and Affordable Ingest Services

With the emergence of centralized, large-scale digital archives, geography becomes a key factor in the preservation of cultural heritage materials. Objects “inside” archives will be actively monitored and managed, whereas those “outside” will be at greater risk of loss and obsolescence. Developing ingest systems and services to process, package and transport objects into managed safe-harbor repositories is an immediate need. Standards, frameworks, and business models for digital archiving must also evolve in due time to support these services.Ingest solutions must address a range of challenges: legal, technical, and financial. Software development, however, is a logical starting point, since tools that automate pre-archiving tasks meet technical requirements for viability and economic ones for affordability. The key tasks to automate are production of preservation metadata, transformation and validation of formats, and creation of repository-compliant transfer packages.The Harvard University Library (HUL) Office for Information Systems (OIS) has developed two applications to promote use of the HUL Digital Repository Service. JHOVE, developed with JSTOR, is a format-validation program; Dmart is a batch deposit tool for audio preservation packages. In Harvard's experience, the target user for such applications has typically been a professional depositing agent with technical expertise, who consults as needed with curatorial experts.With greater understanding of ingest requirements, and the profiles of persons or agencies likely to perform these services, it is hoped that industry will develop and support tools for the digital archiving market.