Ruled out: the use of cyclododecane as a temporary facing during the removal of a canvas lining from a fresco of a kneeling flagellant and Saints Michael and Stephen by Spinello Aretino
This paper is published in the book ‘Subliming Surfaces: Volatile Binding Media in Heritage Conservation’, ed. Christina Rozeik (University of Cambridge Museums, 2018), pp. 155-157.Three fragments of an early fifteenth-century Italian fresco, The Fall of Lucifer by Spinello Aretino, were presented to the National Gallery, London by Sir Henry Layard in 1886. They were detached from the wall above the high altar of Compagnia di Sant'Angelo, or S. Michele Arcangelo, in Arezzo by the strappo technique and lined onto canvas. Movement and shrinkage of the animal glue lining had caused buckling of the fresco, a long-term problem that led to losses from the fragments. A treatment programme to transfer the fragments to solid supports was proposed, using a facing of Japanese tissue paper applied with Klucel G and consolidation with cyclododecane (CDD) to strengthen the structure while the canvas was removed. However, the mordant securing the tin-leaf decoration was found to contain oil and sandarac resin, and there was uncertainty about the effect of prolonged immersion in PET (used to remove the CDD after treatment) on the mordant. The animal glue that holds much of the paint layer together, and some of the pigment binders, were also soluble in water, making the use of Klucel G inadvisable. The Klucel G facing was integral to the treatment plan, so the plan to remove the canvas was abandoned, also ruling out the use of CDD. As a result, the treatment proposal was reassessed in favour of retaining the canvas layer
