The second great era of lost-was bronze casting is undoubtedly the Italian Renaissance. There is literally a rebirth of this technique as the Florentine maestros of the early 15th century, beginning with Michelozzo, became proficient in its methods. Nevertheless, it remained a difficult technique; so much so that Cellini in his autobiography boasted about his ‘epic heroism’ when casting the statue of Perseus.
Treatises such as Birunguccio’s ‘De la Pirotecnica’ in 1550 and ‘De Re Metallica’ by Georgius Agricola in 1530 appeared which muddled bronze casting with experiments in alchemy. Pomponius Gauricus in his
‘De Sculptura’ of 1504 connected the technique to the study of sculptural proportions. Leonardo da Vinci, during the period 1482 to 1493, designed a seven meter high equestrian monument planned to be cast in bronze and dedicated to Francesco Sforza. This extraordinary work sadly was never executed.
The clay used to mould the wax in which the bronze would eventually be poured was found nearby. Beginning with Giambologna, circa 1550, clay was replaced by mud, a more flexible and porous substance containing minced brick and other organic elements thereby rendering it more pliable than clay. This is what we continue to use today in our foundry.
On many Renaissance bronze works, one can see the difficulties that challenged the casters and at times observe as well their mistakes. For example in three of the ten ‘Doors of Paradise’ panels by Ghiberti, one is able to note the gaps and holes which were closed with later bronzing.