J.CAC VOLUME 44 (2019)

A Comparison of Birch Bark Colour Change Due to Methanol or Ethanol Vapour Exposures

Carole Dignard, Season Tse, Sonia Kata, Megan Narvey, Jennifer Poulin

This research assesses whether exposing birch bark to methanol or ethanol vapours as used in treatments to reshape distortions in bark artifacts causes colour changes. Analysis of water, methanol and ethanol extracts of bark by pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) confirmed that methanol and ethanol solvents extract similar compounds in similar relative abundances from birch bark, while water presents a different extraction profile. Three barks of different colours on their cambium sides were exposed to methanol or ethanol vapours for two different exposure periods, and were monitored visually as well as through colour measurements and weight gain for up to 35 weeks after treatment. The short (2.3-day) methanol vapour exposure gave the best results: low colour change combined with fast absorption rate and sufficient peak weight gain to improve bark flexibility. Analysis was carried out on samples of a white crystalline deposit that occurred on one of the barks exposed to ethanol vapour: it was identified as betulin and lupeol in approximately a 2:1 ratio. Cleaning the vapour-exposed barks with swabs moistened with water was successful in removing the white residue and did not in itself cause colour change.

Download: JCAC44 Dignard et al.

J.CAC VOLUME 44 (2019)

Identifying Collections Vulnerable to Disasters: Evidence from Risk Analysis of Rare Events

Irene Karsten

Recent comprehensive risk assessment projects conducted by the Canadian Conservation Institute have shown that, under certain conditions, risks associated with hazards such as fire, earthquake and tornado rank as priority risks relative to all other risks facing heritage collections. Risk analysis using the ABC Method based on incidence and severity data, or on an expert model that relates specific features and behaviours (control levels) with the degree of damage to the collections, can help identify factors that generate Magnitude of Risk scores categorized as High to Extreme for such events. Flood risk scores at least in the High category if collections are stored below or on grade in locations at risk of overland flooding, storm surge or tsunami. Fire risk falls in the Extreme category for collections in combustible or fire-resistive buildings that lack automatic fire detection or suppression and exhibit poor compartmentation, and in many buildings at the wildland-urban interface. Earthquake is categorized as an Extreme risk in non-seismically stable buildings in regions prone to violent or extreme shaking, or as a High risk when the building is stable but storage and display fittings lack seismic protection in regions at risk of at least very strong shaking. Physical damage due to severe winds would score as a High risk in many building types in regions at risk of Category 3–5 hurricanes or EF3–5 tornadoes even when the chance of a direct hit is small. When such disaster risks are categorized as High to Extreme, mitigation is highly recommended and may be cost-effective. Reducing the likelihood of the hazard may be difficult or impossible; therefore, facility improvements that reduce negative consequences on collections during an event are recommended, in addition to preparations for effective response and recovery.

Download: JCAC44 Karsten

J.CAC VOLUME 44 (2019)

Performance Testing of Anti-graffiti Coatings for Painted Outdoor Murals in Canada

Michael O’Malley, Nancy E. Binnie

Outdoor murals are sometimes defaced by graffiti that introduces unwanted painting, tagging or “bombing” on the surface. The purpose of this study was to compare the performance and handling characteristics of ten anti-graffiti coatings and five acrylic varnishes that could potentially serve as anti-graffiti barriers on outdoor murals in the Canadian climate. A selection of both permanent and temporary coatings was made after carrying out a literature search for products available in Canada. Painted test panels were prepared with acrylic latex exterior house paint, following the procedure of a muralist. Protective coatings were applied to each panel based on manufacturers’ recommendations. The panels were aged outdoors for two years, then marked with graffiti materials. Solvents and other methods were used to reduce or remove graffiti marks to determine which coatings provided good protection to the underlying paint. The overall performance of the coatings was assessed on the following criteria: initial and aged appearance (gloss, dirt pickup, colour change), ease of coating application and handling, effectiveness as a graffiti barrier, and ease of local reapplication after graffiti removal. Observations were documented by photographs, videos and notes using customized forms and a standardized rating system. Quantitative gloss and colour measurements were made during the first three years of outdoor exposure to chart the rate and amount of visual change. Of the fifteen coatings studied, many performed adequately as graffiti barriers, but three products were deemed best overall because they performed well across the entire range of the assessment criteria. These included a double-component acrylic varnish system and two aqueous, wax-based anti-graffiti coatings. Overall, increasing the number of applied layers did not adversely affect the appearance of the coatings, and additional layers gave some coatings better resistance to graffiti, as well as protecting the paint layer from solvents and other cleaning methods required for graffiti removal.

Download: JCAC44 O'Malley & Binnie

J.CAC VOLUME 44 (2019)

Book Reviews

Biodeterioration and Preservation in Art, Archaeology and Architecture / Interactions of Water with Paintings / Preventive Conservation: Collection Storage

Download: JCAC44 Book Reviews

J.CAC VOLUME 43 (2018)

Une étude des matériaux et techniques de Marc-Aurèle Fortin

Marie-Claude Corbeil, Elizabeth Moffatt, Claude Belleau, Eric J. Henderson, Jennifer Poulin

A retrospective exhibition of the work of Marc-Aurèle Fortin organized by the Musée national des beaux-arts du Québec provided the opportunity to examine twenty-six paintings executed between 1918 and 1952, along with two artist’s paint boxes attributed to Fortin from the collection of the Montreal Museum of Fine Arts. Samples from the paintings and the paint tubes found in the boxes were analyzed by scanning electron microscopy/energy-dispersive X-ray spectrometry, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, polarised light microscopy and gas chromatography-mass spectrometry. Data on supports, preparation layers, grey and black ground layers and paints are presented here. The painting supports are quite diverse and are sometimes unusual: canvas (linen or cotton), cardboard, wood, fibreboard, metal and linoleum were all identified. The use of poor quality supports is the main conservation problem for Fortin’s paintings, as they may have deteriorated over time or caused alterations to the paint layers. The canvas supports are usually covered with a ground layer, often white in colour, while the rigid supports are not usually prepared, except sometimes those made of cardboard. The composition of the grey and black ground layers, which are characteristic of Fortin, varies from one painting to another, indicating that Fortin did not follow a strict protocol or that he may have employed commercial materials of variable composition. His colours were obtained using a diverse palette: a total of thirty-seven pigments were identified in the twenty-six works studied. Apart from the black ground layers, the binder of which is an oil-modified alkyd resin, Fortin’s paints are mostly oil-based; in some of his later works he also employed casein paints.

Download: JCAC43 Corbeil et al.

J.CAC VOLUME 43 (2018)

The Evolution of Specifications for Limiting Pollutants in Museums and Archives

Jean Tétreault

Since the first pollutant limits for museums and archives emerged in the 1970s, various documents have proposed specifications to guide pollutant control for the protection of heritage collections. Three approaches to avoiding damaging pollutant levels are examined in this paper: specifications based on maximum allowable levels, on dosimeters and on testing products. The evolution of recommended maximum levels of gaseous pollutants is documented, showing that, over time, limits were progressively lowered but then more recently relaxed, and that lists expanded to include more key pollutants. Dosimeters have been developed as an alternate way to characterize pollutant levels, but their use in museums and archives remains limited. Tests that distinguish products that emit damaging pollutants from those that do not have been more widely adopted as a means of selecting appropriate products for use in collection spaces, especially enclosures. To date, evidence to support specifications has often been weak or may not reflect what actually occurs in the museum environment.

Download: JCAC43 Tétreault

J.CAC VOLUME 43 (2018)

How Preventive Conservation Can Inform a Collections Move: Rehousing the Canadian and European Furniture Collections at the Royal Ontario Museum

Greg Kelley, Melissa Maltby

In 2015, the Royal Ontario Museum undertook the challenge of a large-scale, two-year move of over 26,000 artifacts from temporary storage in the McLaughlin Planetarium to a purpose-renovated facility. Moving such vast and varied collections presented many unique logistical and organizational challenges. An innovative approach to designing the storage facility from the ground up by using 3-D modelling software to pre-visualize the various layouts is described. Designs, materials and rationales for dust covers, custom pallets, moving crates and storage mounts are also discussed. This paper focuses on part of the project – the systematic process of moving and storing over 500 pieces of furniture and wooden objects – as an illustration of how conservation can inform a large collections move.

Download: JCAC43 Kelley & Maltby

J.CAC VOLUME 42 (2017)

Practical Electrochemistry for Conservators and Conservation Scientists: Part I – The Basics of Potential Measurement

Lyndsie Selwyn, W. Ross McKinnon

Electrochemical techniques are used in conservation to identify metals or corrosion products, or to monitor or treat metal objects. Although there are many published reports on these techniques, it is difficult to find practical information on how to get started to use them. This paper provides some of this information for one important application of these techniques, namely measurement of corrosion potential (the potential of an object immersed in a liquid electrolyte with respect to a reference electrode). Topics covered include electrochemical cells, multimeters, electrical connection to objects, electrolytes and, especially, reference electrodes – common types of reference electrodes, how to use, protect and maintain them, and how to troubleshoot problems. Examples are given of measuring corrosion potential and using Pourbaix diagrams.

Download: JCAC42 Selwyn & McKinnon I

J.CAC VOLUME 42 (2017)

Practical Electrochemistry for Conservators and Conservation Scientists: Part II – Characterizing and Treating Corroded Metals

Lyndsie Selwyn, W. Ross McKinnon

Electrochemical techniques can be used to characterize corrosion on a metal object and to reduce the corrosion either to a different compound or back to the metallic state. These techniques involve the flow of electrical current, and so are more involved than the measurement of the potential between an object and a reference electrode in a two-electrode cell. Information is given here for techniques where current flows, including the choice of a third electrode (the counter electrode) and the additional equipment needed (a power supply or potentiostat). Examples are given of methods varying the potential (potentiodynamic), holding the potential constant (potentiostatic), or holding the current constant (galvanostatic). The following aspects are discussed: identifying the features associated with oxygen reduction, associating the peaks in potentiodynamic scans with specific compounds in the corrosion, choosing the potential for treating an object, and estimating the amount of corrosion on an object or a test sample.

Download: JCAC42 Selwyn & McKinnon II

J.CAC VOLUME 42 (2017)

The Treatment of a Catharine Parr Traill Botanical Album

Christine McNair

A treatment was undertaken at the Canadian Conservation Institute to conserve a botanical album compiled by Catharine Parr Traill from the collection of the Peterborough Museum and Archives. The botanical specimens, many detached, were vulnerable to mechanical damage due to the stiffness of the binding. After consultation with conservators at the Canadian Museum of Nature, a treatment method was developed to reattach the detached specimens using micro solvent-set straps of Japanese paper. This solvent-set strapping interfered minimally with the movement of the book’s pages and was comparable to methods used within herbariums. The strips are easily reversible and require minimum moisture and adhesive. Some portions of the specimens were lightly adhered using methyl cellulose. The binding itself was structurally altered by adding a moulded spine hollow in order to improve the opening of the volume and to prevent further mechanical damage.

Download: JCAC42 McNair