Treatment of Acid Hydrolysis of a 1900 Large-Scale Composite Artwork by the Artist Roberto Sebastian Matta: Comparison between Traditional and Innovative Deacidifying Methodologies

This work was carried out for a master’s degree thesis concerning the conservation of a contemporary artwork made by the surrealist artist Roberto Sebastian Matta. The artwork is a large (one central panel 180.3 × 405.1 cm; two side panels 179.1 × 150.6 cm) triptych created in 1974 with pastels on tracing paper adhered onto canvas as a secondary support. After thoroughly studying the execution technique and conservation status of the artwork, several issues arose, including a strong acid hydrolysis of both the paper and canvas supports. We focused our intervention on deacidification treatments by comparing either traditional substances, such as calcium propionate in an alcoholic solution, or more innovative methods, such as a nanostructured calcium hydroxide in isopropyl alcoholic solution. Acid hydrolysis degradation was the most difficult issue to address because of the size of the artwork and for the different sensitivities to aqueous methods of the materials used to make the artwork. For the first time to our knowledge, we used an innovative deacidification method consisting of nanostructured calcium hydroxide particles. This intervention would allow the homogeneous atomization of the deacidifying agent in alcoholic solvents to be safe and effective for the work as a whole.