Tru Vue Blog: Conserving Canvas Symposium
Hazel Neill attended the Conserving Canvas Symposium was funded by the Getty Foundation and hosted by Yale University’s Institute for the Preservation of Cultural Heritage, New Haven, Connecticut between, 14-18th October 2019. It forms part of the Getty Foundation’s Conserving Canvas Initiative.
It was the first international symposium on the structural treatment of canvas paintings since the Conference of Comparative Lining Techniques at the National Maritime Museum in Greenwich in 1974.
In this report, I will give a personal response to the wealth of information presented over four very enjoyable and intensive days. I am very grateful for the generous support provided by Icon and Tru-Vue in enabling me to attend this important event.
The papers given were focused on broad themes such as history, principles and theory, present practice, research and the adhesives question with varying perspectives and approaches from conservators from all over the world, including North America, Russia, Europe, India and Korea. The diversity of materials and techniques employed historically and in current practice was unsurprisingly varied; many case studies were presented.
The Adhesives Question
There is a very wide range of adhesives at our disposal, from water based to water repellent. With regards traditional lining techniques, whilst wax-resin based lining was generally discussed only in terms of historical use or methods of reversal, there was much discussion around the positive advantages of flour/glue paste lining. Favourable qualities being the accessibility, affordability and green credentials, the reversibility and the fact that the degradation processes are very well understood. This in contrast to the comparatively limited data regarding long-term ageing of many modern hot melt or solvent activated adhesives.
It was acknowledged that as a profession, we are reliant on other industries for access to and the consistent quality and formulations of many adhesives, particularly modern polymers. When it is considered that future regulation of certain toxic chemicals, commonly found in formulations, such as Beva 371, would affect availability and jeopardise subsequent reversibility of these materials, then perhaps, the development and modification of the non-toxic, natural and affordable ingredients in flour based adhesives could be a positive future direction. Current research into the potential of nano-cellulose was also presented.
What is a lining for?
There seemed to be a general feeling of greater acceptance of slight surface deformation and that the integrity of the tensile properties of a canvas painting should be preserved. Separating structural treatments into a series of stages allowing for a bespoke approach seemed to have popular support. However, there was also support for the traditional technique of addressing all structural issues with lining in certain circumstances. Mikkel Scharff suggested that an overview of treatment options in the form of a flow diagram, possibly with reference to risk assessment would be a useful tool in decision-making.
Understanding the complexity of canvas
With regards canvas, the discussion was broad, covering early open weave linen canvases, through to futuristic tri-axial weave canvases with improved fracture toughness and stiffness and self regulating smart fabrics with embedded sensors for force, moisture and strain.
Christina Young outlined the complexity of woven canvas and the influences that yarn type, fibre shape, weave and permeability have on its behaviour. The deepening complexity when surface coatings with differing tensile and shear factors are applied to canvas was mentioned and it was acknowledged that the question, as to what the dominant contributing factors to the behaviour of oil paintings on canvas are, needs further research.
A recurring theme was the importance of mock-ups, for example: to study mechanical performance and failure mechanisms, to create material reference sets and to gain a better understanding of the impact of variations in recipes and lining fabric choices. Many institutions and research projects plan to disseminate their results through the development of reference databases: Both the Smithsonian American Art Museum and Brooklyn Museum plan databases on wax-resin lining whilst the Universidad Complutense of Madrid and their European partners have developed an interactive database into the 300 years of the use of ‘gatcha’ paste lining techniques throughout Europe. These databases will go a long way to filling the knowledge gap in the profession.
Retreatability – a more achievable aim then reversibility
The reasons for lining and the question as to how to recognize when an old lining has failed were covered and there were papers on the reversal of both Beva 371 and wax-resin linings. Caution was advised regarding the latter as there is insufficient data to enable a complete understanding of what is removed; the wax will melt at 40 C but the resin could be left behind increasing the acidity within the painting.
The continued acidity of oil paint layers was a feature of Stephen Hackney’s keynote address as was the need for more understanding of the ‘critical roll of the size layer, its actions and vulnerabilities’. He cautioned against the use of acidic lining adhesives, particularly when paintings are to be completely sealed within frames as low air exchange leads to a concentration of volatile reactions and greatly increases the rate of deterioration. Framing systems should be ‘leaky’; this has relevance to the problem of hazing of the glazing within sealed frames. In his paper, Dale Kronkright, from the Georgia O’Keefe Museum, espoused the importance of backing and glazing to limit canvas displacement, velocity and strain during transit so perhaps slight alterations in the sealing of backboards when paintings are loaned is the answer?
It was encouraging to learn about simple and innovative solutions: the use of unwaxed dental floss and packing tape for tracking systems and the use of Gortex suture needles for tear repairs. The proven effectiveness of early cloth backings on paintings at the V&A and the protection against fluctuations in relative humidity afforded by loose lining was illuminating. It was exciting to hear about the development of adhesive meshes and the use of ‘The Pool Method’ to activate lining adhesive using hot water.
Overall, there was a consistent call for more data, for more online resources and master-classes on how best to interpret the data and for the development of a coherent, universal standardisation of terminology. There was also a proposal to encourage more publication of structural treatments in both museum and private practice.
The symposium was wonderfully well organized. The herding of almost four hundred delegates between two buildings and across two roads twice a day was a masterclass in coordination and teamwork. The papers were first rate and the opportunity to meet conservators from across the world was cannot be underestimated. I await the post prints with interest.
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All images: Hazel Neill.