42nd Annual Meeting – Joint PSG/WAG Session, May 31, 2014, “Recent Developments in the Evolution of Spring-loaded Secondary Supports for Previously Thinned Panel Paintings”, by Alan Miller and George Bisacca

In his presentation, Alan Miller, Assistant Conservator in Paintings Conservation at the Metropolitan Museum of Art in New York, showcased recent developments of spring-loaded secondary supports attached to the back of panel paintings.
He began by reviewing how usual 19th and 20th century treatment of warped panel paintings involved severe thinning of panels along with the application of wood “cradles” on their backs to straighten them and provide “support”. This portion of the presentation wonderfully complimented Karen French’s earlier talk on the evolution of the structural treatment of panel paintings at the Walters.
As Karen did in the morning, Alan discussed the consequences of past treatments on the panel and its painted surface. New treatment approaches have evolved over the past two decades with the development of flexible supports attached to the back of panels, allowing for the natural curvature of the wood and its movement in response to changes in relative humidity. Specific consideration was given to previously thinned panels, very vulnerable once their cradle is removed. Alan provided a review of the development of the spring mechanisms they developed with George Bisacca these past years, referring to the Getty Conservation Institute’s panel paintings initiative (link: http://getty.edu/conservation/our_projects/education/panelpaintings/panelpaintings_component1.html)
The presentation was generously illustrated with images of the various spring mechanisms developed at both the Istituto Superiore per la Conservazione ed il Restauro (ISCR) and later by Bisacca and Miller, explaining the pros and cons of each. For instance, the earlier conical spring designed at the Istituto allowed for much movement but required thickness of the wooden strainer attached to the back of the panel painting, an issue in terms of flexibility of the strainer, not to mention weight and volume. On the Met’s most recent strainers, which are much thinner, grooves are cut cross grain and filled with a silicon based material for added flexibility. Miller emphasized the importance of the number and placement of the springs attached to the back of a previously thinned panel.
He listed the criteria established for the development of spring mechanisms specifically designed for previously thinned panels: springs should be as small (contained) as possible to allow for a thin strainer, easy to adjust, economical and re-usable. Most recently their work has focused on a thin laser cut disk spring, associated with a flexible threaded nylon screw, which allows light weight, flexibility and fine adjustment.
This talk provided very valuable information on recent developments in the treatment approach of wooden panels, applicable not only to paintings but possibly to furniture or architectural wooden panels.