The circulation of building materials: pozzolana in the Baroque Dubrovnik Jasenka Gudelj University of Zagreb Abstract The paper investigates the introduction into Early Modern building practice in the Republic of Ragusa (Dubrovnik) of pozzolana, a component of hydraulic cement, thus extending the area where it was known to have been used in the Baroque era. The documents in the State Archive in Dubrovnik reveal that this granulate was first sent to Dubrovnik – along with projects and a master-builder from Rome – on the occasion of the rebuilding of the cathedral after the great earthquake of 1667. The scepticism of Dubrovnik authorities towards the new material is analogous to the almost contemporary French discussion relating to Bernini’s Louvre. By contrast, the 18th century Ragusan documents express the necessity of pozzolana for the hydraulic works commissioned from the Roman architect Pietro Passalacqua, in a manner similar to those for contemporary projects in Ancona or Venice. These episodes illustrate an otherwise poorly-documented process of changing building technology, and they introduce the importance of pozzolana in the epistemology of architecture as one of the materials which is not only resistant to water, but also is effective in resisting the actions of frequent earthquakes. Keywords Pozzolana, hydraulic cement, earthquake, Dubrovnik, Stjepan Gradić, Pier Andrea Bufalini, Louvre, Gianlorenzo Bernini, Pietro Passalacqua, 17-18 th century Introduction The international trade in building materials in the Adriatic area, which was already active in classical antiquity, especially flourished in the Early Modern period, when the so-called pietra d’Istria, a high- quality limestone to be found in both Istria and Dalmatia, became a much-desired cladding material for the façades in Venice, as well as in Marche and Emilia-Romagna. 1 The forests of Adriatic oaks and pines also supplied the wood to be used in ship-building, as well as in the other structures. 2 Given the volume of stone and wood used and exchanged between the two coasts of the Adriatic, it is understandable that the scholarship has concentrated on the circulation of these building materials and has provided insight into Early Modern technology and the economy of construction in the area. By contrast, considerably less attention has been given to the binders used in historical buildings in the East Adriatic area, where there was an important and often distinctive element of construction. The present paper investigates the introduction into Early Modern building practice in the Republic of Ragusa, now Dubrovnik in Croatia (Fig. 1) of pozzolana or pozzolanic ash, a type of sciliceus volcanic ash which, when mixed with lime and water, forms a waterproof, hydraulic cement. It is named after the town of Pozzuoli in Campania near Naples, where the most copious deposits of the highest quality material are to be found. Pozzolana was well known in antiquity and described by Vitruvius, 3 but did not form part of the East Adriatic tradition of using cut stones and lime mortar. The importation of this binding component to 61 Jasenka Gudelj