the Archaeology Service of Barcelona City Council The pieces from archaeological excavations reach from prehistoric times to contemporary times. As part of the archaeological intervention of Torre de la Sagrera air raid shelterwhich will soon be opened to the public after being rehabilitated and converted into a museum. Rubber soleThe shelter was closed after the war, and in 2014, it was discovered intact during rehabilitation and expansion works of the building.
At this site, archaeologists found a rubber sole belonging to someone seeking shelter in a bomb shelter during the Civil War. It is not known who it belonged to or what type of shoe it was, although it may be possible due to the material and design. From espadrillesbut it is not known for sure. For the Municipal Antiquities Service, this is a unique piece, as it is the first time this archaeological material has been found and the conservation procedures were a great challenge.
The first step was to obtain information through existing bibliographies and seek advice from the Canadian Institute of Conservation, a reference in the field for contemporary materials, as well as contacting the French restorer specializing in plastics, Sylvie Ramel. In both cases, experts advise: It was necessary to know whether the rubber was natural or synthetic. Because the preservation treatment varies from one species to another. For this reason, a sample was sent to the Chemical Institute in Sarria for analysis and to determine that it would most likely be Natural rubberAlso taking into account the age of the object which is more than 80 years.
After the results, the most appropriate treatment was chosen. Lack of oxygenThis method consists of keeping the body isolated for a certain period in a special plastic bag and leaving it without oxygen by introducing an inert gas such as nitrogen through a generator in order to eliminate wood-eating insects such as mites or microorganisms that could damage the object. This entire procedure was carried out in collaboration between the Archaeology Department of the Barcelona City Council and the Higher School for the Conservation and Restoration of Cultural Assets of Catalonia, part of the State’s Ministry of Education.
When an organic piece arrives, the previous step is Make sure it is clean.“The lack of oxygen was introduced to replace the toxic chemicals that were previously necessary to carry out this task,” points out Rosa Rocaberra, biologist and science and technology teacher at the school responsible for this intervention, who highlights the work in this field of the pioneer Nieves Valentín Rodrigo, from the Institute of Cultural Heritage in Spain.
On the other side, Natural rubber emits gases. Which does not harm the piece, but it does harm those around it if it is kept in a warehouse, as is the case in the Zona Franca Collections Center. “The lack of oxygen has a double function: to preserve the objects in the long term even if they do not contain microorganisms, and to prevent the surrounding objects from deteriorating. “Here we do not do restoration but preventive or curative conservation,” confirms Cosi Colonna Preti, conservator and restorer at the Barcelona Archaeology Service.
“In archaeology, it is unusual for such a rubber sole to be preserved due to the nature of the material because the organic material is very strange and unusual. In this sense, we are thinking more about other materials such as ceramics, glass or metals,” adds Joan Escudé, secretary of the Higher School for the Conservation and Restoration of Cultural Assets of Catalonia.
After a week of hypoxia and a satisfactory result, the sole was returned to the custody of the Barcelona Archaeological Service. After a period of observation and once the piece is considered stable, like all archaeological material, it will become part of the archaeological archive managed by the Barcelona History Museum (MUHBA).
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