Recognized as one of the greatest masterpieces of Romanesque art in Europe, the Portal of Glory is an architectural and sculptural ensemble in the narthex of the Santiago de Compostela Cathedral in Galicia, North-West of Spain.
The monument, of approximately 17 meters long by 10 meters high, was built between 1168 and 1188 under the direction of Maestro Mateo, and served as the main entrance into the cathedral until the XVI century, when the outer façade was built. It consists of three semicircular arches with over 200 polychrome figures of great realism and expressiveness. The central arch contains a depiction of Christ, surrounded by the representation of apostles, prophets, and evangelists. Both semi-arch sides display scenes from the Old Testament on the left and from the Final Judgment on the right. The whole scene is chaired by the central archivolt representing the 24 Elders of the Apocalypse, tuning their musical instruments.
The Portal of Glory represents the most distinctive and recognized element of the Santiago de Compostela Cathedral, and is the destination for the millions of pilgrims who have made the Way of St. James (Camino de Santiago) throughout the centuries.
The ensemble suffered an alarming deterioration, mainly due to the effects of environmental phenomena, inappropriate treatments used in previous interventions, and certain popular traditions. The stone materials and the Polychrome layers suffered of a number of damage processes such as discoloration and stains caused by biological growth, dust and dirt; efflorescences of nitrates and chlorides coming from percolations of water into the structure; seritic alteration, arenization, pulverization, fractures and loss of fragments of material. Polychromy was losing its adhesion to the stone, mainly due to the crystallization of soluble salts and to the weathering of the preparatory layer.
The preventive conservation and restoration project of the Portal of Glory was carried out with the exclusive patronage of the Barrié Foundation with the aim of not only preserving this masterwork of Medieval Europe, but also to convey to society its historical-artistic value, as well as the importance of heritage conservation. This Project is the most recent and ambitious one of multiple restoration projects the Barrié Foundation has undertaken in the Santiago Cathedral such as the restoration of the stone choir of Master Mateo or the reconstruction of the instruments of the Portal of Glory, among others. The Spanish Institute of Cultural Heritage of the Ministry of Culture was responsible for the technical coordination of the project, with the support of a Scientific Advisory Committee, composed of internationally-renowned experts in the fields of Art History, Biology, Architecture, Physics, Archaeology, Chemistry and Geology. The historical and technical-scientific expertise provided by these teams has led to what may be the most comprehensive study of the Portal of Glory to date.
The project started in the year 2006 and was executed in three phases over a 12-year period. The first phase involved conducting a multidisciplinary investigation about the state of conservation of the monument and the main causes of its deterioration. The investigation included historic and archival research, structural studies, mineralogical analyses, biological sampling, cleaning tests and microclimatic monitoring. This multidisciplinary investigation allowed an integrated assessment of the main risks for the conservation of the Portal and their prioritization according to their potential of damage. The second phase involved taking the necessary measures to neutralize deterioration processes. Through the preliminary investigation it became apparent that the main responsible for the observed damage was the infiltration of rainwater through the roof, due to cracks in the structure of the basilica. Repairing the roof and western façade was imperative before moving forward. The urgency to undertake these repair works led to the approval of a 17 million euro contribution from the central administration to address the general deteriorating condition of the cathedral. Measures to stabilize the environment were also implemented before conservation treatments began, and included repairing doors and windows to prevent air exchange and the installation of an environment control system.
The third and final phase entailed the implementation of treatment methods. The conservation team followed a minimal intervention approach, based on removing superficial harmful deposits that could affect the stability of the historical materials, such as dirt, salts, biological remains, acrylic accumulations, and unstable mortars placed in previous interventions. During this phase, the existence of three polychrome stages, in addition to other more recent partial proceedings, was confirmed. The few remains of the first original polychromy revealed that the Portal of Glory was originally decorated with the most vivid pigments (lapis lazuli, vermilion, red lacquer, green lacquer, lead white and black bone) and precious materials (pure gold and silver leaves,…), which illustrate the powerful symbolic and liturgical role the Portal of Glory played in the Middle Ages. The second layer probably dates from the XVI century, when the western façade was built, whereas the third was certainly conducted in 1651, as documented in the archives of the cathedral
Every phase of the project and every figure of the over 200 featured in the monument has been digitally documented through Sandstone, a heritage documentation software created by the World Monuments Fund in collaboration with the Santa María Cathedral Foundation, the Santiago Cathedral Foundation, the Spanish Cultural Heritage Institute (IPCE) and the Barrié Foundation. This software centralizes and organizes all the information gathered by techniques such as photogrammetry, digital photography and others, creating an exhaustive, easily accessible repository for any future intervention in the monument.
Throughout the period, the Barrié Foundation organized educational activities to disseminate knowledge about the Portal of Glory and to create awareness for heritage conservation. From the early phases, guided tours on the scaffoldings were organized to let visitors admire the monument at close quarters and to learn more about restoration work. As the project progressed, a series of publications were edited and a number of exhibitions and scholarly seminars were conducted in several locations – including London, Boston, Berlin, Lisbon, Madrid, Santiago de Compostela, Burgos, and Pamplona. These activities were enthusiastically received by over two million users.
This decade-long restoration project, with 50,000 hours of work and 6.2 million Euros invested, has helped eliminate the layer of dirt, salts, biological remains and acrylic accumulations that covered the surface of this masterpiece of Maestro Mateo, and recover the various layers of preserved polychromy, thereby assuring that it is preserved for future generations. The project is not only an example of private patronage in heritage preservation, but bringing together the central and regional administrations (Ministry of Culture and Xunta de Galicia) and two private institutions (the Barrié Foundation and the Santiago de Compostela Cathedral), the project is also an example of institutional collaboration for the conservation of Cultural Heritage.