9th International Conference on NDT of Art, Jerusalem Israel, 25-30 May 2008 For more papers of this publication click: www.ndt.net/search/docs.php3?MainSource=65 STUDY OF THE QUATERNARY ALLOYS IN THE CAST OF THE EQUESTRIAN STATUE OF BARTOLOMEO COLLEONI BY ANDREA DEL VERROCCHIO (VENICE 1480) AVAILING OF EDXRF SYSTEMS Lorenzo Morigi1, Stefano Ridolfi2 1 Giovanni e Lorenzo Morigi Restauratori, Bologna, Italy, E-mail:
[email protected] 2 Ars Mensurae, Rome, Italy, E-mail:
[email protected] ABSTRACT The Bronze equestrian statue of Bartolomeo Colleoni by Andrea del Verrocchio, cast between 1466 and 1490 by Alessandro Leopardi in Venice, is composed of several parts connected together availing of casts-on. The statue was analysed using a transportable EDXRF system in situ during the restoration of the monument, applied to 21 chosen areas, with the aim of characterising the alloys that compose the different parts of the statue. The areas to be measured were chosen so as to include every sub-section of the statue, therefore every part underwent at least one quantitative analysis. The metal used in the casts-on is a quaternary copper, tin, lead, zinc alloy, while the rest of the sculpture does not contain any trace of zinc, composed as it is of the classic ternary (copper, tin, lead) bronze alloy. Considering the amount of metal required to make the casts-on, the shapes into which they were moulded and, therefore, the economic cost of every single cast-on, the artist’s intention to exploit the strength of the copper alloys containing zinc to obtain sufficiently strong soldering between pairs of different casts is clear.