Wednesday, January 22, 2014

Perseus by Benvenuto Cellini - the sculpting technique (1)

This post will be a little longer than usual, as it tends to describe (adapted from French Wikipédia) the whole process to create this stunning Perseus sculpture.

The thinking process before the sculpture

Because of the many fragile parts (sandals' wings, sword, raised arm with Medusa head, etc.) to be sculpted in marble, Cellini decided to do a bronze sculpture, despite the planned height of 6 meters.
To facilitate the making, and also for aestethic reasons (as the proportions for a 6 meters statue would have been too disparate) he divides in 2 the planned height. From right foot to Medusa head, the final height will be 3.20 meters, in addition to the 3 meters base to be sculpted.

Cellini is willing to cast the statue in one unique piece, even though it is a very imposing height, as he wants to avoid the problems encountered by Donatello and his Judith sculpture. That sculpture was made with 11 different parts, melted separately then welded. But doing this it was showing variations in colors, in thicckness, and the weldings were too visible. Cellini did not wanted that at all.

Also, as the Perseus was planned to be located below one arcade (see picture below), and not leaning against a wall, Cellini wanted the sculpture to be beautiful and full of harmony from all faces. Eventually, he wanted to sculpt the 4 faces from the base with bas reliefs, to develop and enrich the myth.


Cellini will first start with the Medusa head, then Perseus, then the base. The challenge is enormous, because the technique to mold a bronze statue so high was lost since Antiquity.
To succeed to cast the statue in only one piece, Cellini will use the lost wax technique, in which the sculpture is made in wax, on a mold in clay. The was is then covered with clay. Then the wax is melted and lost. Bronze is then cated between the two layers of clay. Once the bronze is cold,  refroidi, the outside mold is broken to reveal the sculpture.


Before to start with Medusa bronze, Cellini does some experiences, like with the clay to be used for the molds. He does a Julius Cesar bust, which confirms his choices. Then, to be fully sure about his technique, and to please the Florence Duke, he does a Cosme Ier bust.

Now that he is 100% reassured on the clay quality, he starts the Medusa cast. As she has to stand on a small surface,  he decides to display her body on a shield and on a cushion.The cushion reminds the bed on which Medusa was surprised by Perseus while she was sleeping.

The shield evokes the one that Athéna gave to Perseus to allow him to be close from Medusea without being transformed into stone. Legs are folded in a unsual angle, while the left arm grips one ankle, and the other arm lays lifeless along the base. From the beheaded neck, a river of blood leaks, quite a strong vision for that time.

It takes Cellini two years before to unmold Medusa. The result is impeccable. It earned him the esteem but also jealousy. Cellini must even defend his project with the Duke, who is very impatient and has doubt, like the others, about the ability to cast the imposing bronze Perseus. Cellini succeeds to persuade him with lots of technical arguments, but the relationship between the two men remains fragile.



Despite the tension and fear of failure, Cellini starts the making of Perseus. Because of its size, the statue must be empty, otherwise the weight of the bronze would make it impossible to move. To do this, it takes a special mold.

Cellini first solidifies the mold with iron bars, to support the wire mesh that draws the first contours of the statue. It then prepares the clay that will cover the trellis. This clay, taken near Florence, has been carefully chosen and prepared first with pieces of sheets. After mixing them until a smooth paste, Cellini sprinkles and knead it for several months. The wad of cloth eventually rots and provide a smooth creamy mixture, easy to work with . The resulting clay will dry evenly without risk of causing imperfections in the casting.

When ready, Cellini applies it on the frame and shape it for several hours to form the earth core of the mold. Before being coated with wax, it must be perfectly dry. The mold is first left to dry outdoor, without cracking. Then, it is heated in the fire to remove any moisture that might burst the clay at the time of casting bronze.

The next step is to cover the core with a layer of wax of similar thickness to that of the desired metal sculpture. Soft wax is also used to shape the details of the statue (face, muscles, visible veins, etc.). The wax itself is the subject of careful preparation. It should be smooth and tender at the time of application. It must then dry securely to withstand the weight of clay that will cover it. No error is allowed, because the final result depends heavily on the shaping wax.

Once this work is completed , which already shows the final appearance of the statue, the core and the wax need to be covered with clay. At this point, it is important to provide a system of tubes through which the molten metal goes down into all areas of the mold, while allowing air to escape. These tubes are also made ​​in wax , before being covered with clay.

Cellini in his workshop working on Perseus project
To avoid damaging the wax, and therefore create damage to the sculpture, the was must first be covered with a protective mixture made of ... marrow from calcined horn sheep bone, with plaster, Tripoli rock powder, iron filings, water, all that filtered through a sive made of horse manure!

The resulting preparation is applied using a brush made ​​with pig bristles. The operation is repeated several days, layer after thin layer, allowed to dry between each application. This protective layer may then receive successive clay coatings, while maintaining the drawing of the wax, now well protected.

Now, the wax trapped between the core and the outer layer needs to be removed. It is this gap which will then be filled by the bronze at the time of casting. A first fire drying takes place. Then, a stove of four meters high is built around the mold to finish drying.

The wax flows through the tubing created by the wax sticks . The mold is now ready to receive the bronze.

Part 2 will show the last part of this sculpture achievement, and the reactions once it was unveiled.