Restoration of the Roman mosaic of Borja (Bursao)

INTRODUCTION

The restoration of the Borja mosaic was a long-delayed priority until September 2021. It was then that the Borja Town Council urgently promoted the start of work on the restoration and conservation of this important heritage asset.

Francisco Javier Gutierrez, the archaeologist in charge of the Bursao archaeological site, gives a brief description and explanation of the discovery.

Description

“In 1986 archaeological remains were discovered by chance in what is now the “Torre del Pedernal” site, in the municipality of Borja (Zaragoza).  During the excavation, a Roman house built at the end of the 1st century A.D. was discovered. It consisted of several rooms and a hortus around which the rooms were distributed.  This mosaic was located in Room 1.

Sketch by F.J. Gutiérrez

Sketch by F.J. Gutiérrez

In 1986 an emergency excavation unearthed some Roman rooms in the periurban area of Borja (Zaragoza), known as “El Pedernal”. Room 1 had a tessellated pavement floor that we presented in 2022, recently restored and installed, in the municipal archaeological museum of Borja.

It has a bipartite decorative composition, so it may have been a representation room, perhaps a triclinium where the lords ate and drank while chatting in a reclining position.

The rectangular part has a black-and-white grid composition with circles at the intersections, and is ornamented with moulded wreaths and curved leaf stems at the corners.

Virtual reconstruction on the sketch of the restored fragments

Virtual reconstruction on the sketch of the restored fragments

In the second part there is a square composition based on a tangent inscribed circle inside which a triaxial honeycomb composition is presumed to have developed. Its central motif has been removed and may contain figures, such as mythological figures and allegories. A flower and four-petalled florets and isosceles triangles can be recognised. The corners of the square are occupied by calyxes from the base of which scrolls with ivy leaves emerge. This field is framed by a saw-toothed band. A bichrome border surrounds the entire composition.

Dating and chronology

The restoration process carried out by the Borja Town Council has documented several layers of its composition, as can be seen in the attached image.

Strata on the floor of the mosaic pavement

Strata on the floor of the mosaic pavement

From all that has been analysed, the polychromy, the figurative themes and the florid style, this mosaic could be dated to between the second half of the 2nd century AD and the beginning of the 3rd century AD. In this case, and with a marked Italic background, the Gallic influence is evident in the main honeycomb composition. The closest parallel can be found in Room 7 of the domus in Calle Murallas in Zaragoza”.

Project and treatment

The Roman mosaic of Bursao was excavated (1987) and shortly after it was extracted. However, as it was not subsequently museumised – at the time there was no programme or museum for it – the mosaic has suffered various vicissitudes up to the present day. Thus, what at the time would have been a fine-tuning of the mosaic for its future conservation and museum display, has become a complex restoration work. Promoted by the Borja Town Council, there was a previous project by José Antonio Rodríguez Martín, then the restoration of the mosaic has been initiated. Santiago Ortega Sánchez-Diezma was hired Santiago Ortega was hired as a team with Mª Pilar Camón Urgel y Elena Naval Castro to carry out the project for the restoration and conservation of the mosaic pavement opus tessellatum of Bursao.

In situ extraction plan by Mª Luisa González Pena and José Antonio Minguel and scale measurements by archaeologist F.J. Gurierrez.

In situ extraction plan by Mª Luisa González Pena and José Antonio Minguel and scale measurements by archaeologist F.J. Gurierrez.

Emergency intervention

Restoration work on the mosaic began with the transfer to the workshop of all the existing mosaic fragments from those removed in 1987. For the treatment and restoration of the mosaic, a suitable and specific location was provided. And for its future conservation after restoration, it was decided to install and mount it in the Borja Archaeological Museum.

The Borja Town Council provided auxiliary and human resources.  The archaeologist Francisco Javier Gutiérrez González provided documentation, such as measurements and the most up-to-date historical-artistic and technical studies to date. There was a great shortage of graphic documentation from those years when the extraction was carried out.

Removal of the plastic wrap from the fragments

Removal of the plastic wrap from the fragments

Treatment

The process began with the transfer of the 28 extracted fragments to the working room for treatment and intervention. Those were marked, numbered and bagged during the extraction campaign in 1987. Immediately after, after identification and graphic documentation, was to consolidate each of the fragments. The whole had suffered wear and tear due to long storage. It was therefore urgent to fix and secure fragments and tesserae from the beginning of the procedure.

The fragments bore different layers of substrates

The fragments bore different layers of substrates

The restoration  of the mosaic basically consisted of recovering and securing the mosaic pavement, fixing the large number of tesserae that were loose and moved. To do this, it was first necessary, and sometimes simultaneously, to remove a large number of layers of substrates and mortars that were adhering to the back of the mosaic. These tasks were the most systematic and insistent of the process, given the state of preservation of all the fragments in general. Subsequent treatments required the fragments to be freed from the thick layer of substrates they were carrying. We also adhered and fixed the pieces of the broken and loose fragments. And the tesserae that were loose, especially at the edges, which had suffered a great deal of wear and tear,

Repositioning of loose tesserae

Repositioning of loose tesserae

Cleaning and surface consolidation

We remove the gauze crimp from the extraction of the fragments after they have been consolidated. We then removed the remains of glue and adhering materials. In some cases, too, the control numbering written on the extraction setting had penetrated and reached the surface of the tesserae.

Installation in the museum

An important and very necessary step was the placement of a mobile support for its future installation and assembly in the archaeological museum of Borja. For this purpose, a honeycomb panel was adapted to the fragments, basically made of aluminium and fibreglass. This inert material makes it extremely resistant and light at the same time. Beforehand, in order to prepare the adaptation, a homogeneous consolidation and levelling mortar was applied to each and every one of the fragments. Likewise, the edges were also reworked with the mortar, which plays an important role in the mechanical consolidation of each of the fragments. And all of this paying attention to where and how the joints between the fragments would be.

The archaeologist Francisco Javier Gutiérrez was in charge of the musealisation and educational content of the cultural property.  He was also responsible for the interesting explanatory panel that accompanies the exhibition of the mosaic in the museum.

“Pedernal” Mosaic Poster

Initial installation in the Archaeological Museum of Borja

Initial installation in the Archaeological Museum of Borja

More information on other restoration work;

The restoration of paintings on canvas

 

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