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Friday, May 17 • 2:00pm - 2:30pm
(Paintings) The Role of Nonpolar Solvents During Re-Adhesion of Absorbing Substrates with Acrylic Dispersions – New Insights on an Old Technique

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In this paper the role of nonpolar solvents during re-adhesion of absorbent chalk ground and canvas with acrylic dispersions is investigated. To optimize the penetration of dispersions into a delamination gap or into a porous paint, some recommend nonpolar solvents such as white spirit for wetting the surface (see product data sheet of medium for consolidation and the publication of Hedlund and Johannson 2005, p. 438). Others, for instance Rowe and Rozeik, bring up the question regarding the difference between Cyclododecan and white spirit as masking agent to prevent penetration of a water-based adhesive when stabilising lifting paint flakes." (2008, p. 22). However, the mechanism has never been clearly shown. The question is: can nonpolar solvents serve as pre-wetting agents as well as masking agents, which is the complete opposite of wetting? If yes, how can this be controlled? First tests were carried out at the University on Applied Sciences on samples, afterwards one case study was undertaken. Test samples of absorbent paint on unsized flax canvas were produced. Subsequently, fluorescent-dyed acrylic dispersions (medium for consolidation, Plextol D 498 and Pelxtol B 500) were applied using different application methods (micro pipette, precision-micro dispensing system and heat spatula). Two aliphatic solvents (white spirit and Shellsol T) were tested. For the re-adhesion of flakes on canvas, a rigid open-celled foam was used as underlying support. The foam was used to guarantee the least possible contact to the backside of the canvas in order to minimize capillary forces. VIS and UV-light photographs of the back of the canvas and the glue interface were taken in order to calculate the adhesive distribution. Thin sections of the samples showed the dispersion remains in the canvas-glue paint stratigraphy. Adhesion was observed first by hand in order to clarify the influence of material choice and application method. The most relevant samples were then tested with the tensile strength machine. The paper will clearly show that nonpolar solvents can serve for wetting as well as for masking. The results are demonstrated by means of tensile tests and the penetration through fluorescent-dyed dispersions. As a consequence the research study will enable conservators to control the adhesion and penetration by varying the evaporation time and the applied volume of the nonpolar solvent as well as the substrate and the glue.

Speakers
avatar for Karolina Soppa

Karolina Soppa

Prof., head of the painting and sculpture specialisation, Bern University of the Arts, Department of Conservation and Restoration
Karolina Soppa graduated from the Stuttgart State Academy of Art and Design (Germany) in 2006 with a diploma in Conservation and Restoration of Paintings and Painted Sculptures (thesis on the penetration of polybutylmethacrylates in canvas paintings). After working for half a year... Read More →


Friday May 17, 2019 2:00pm - 2:30pm EDT
Salon B2, Uncas Ballroom
  Specialty Session, Paintings