In the same tradition of international good will as France’s gift of the Statue of Liberty, the United States recently presented Italy with Il Cavallo, the world’s largest bronze sculpture of a horse. The gift honors the Italian people for 2,000 years of cultural heritage; recognizes the noble horse as a bearer of man and messages for centuries; encourages curiosity, imagination and creativity among youth; and commemorates Leonardo da Vinci, the Renaissance’s greatest universal man. To fully understand the significance of Il Cavallo (Italian for “The Horse”), its history must be traced back more than 500 years.
In 1482, the Duke of Milan commissioned Leonardo da Vinci to design the world’s largest equestrian sculpture. Da Vinci used his keen grasp of animal anatomy to design and produce a 7,3m (24 ft) clay model of his planned bronze sculpture. But on September 10, 1499, France invaded Milan and French soldiers destroyed da Vinci’s clay model by using it for target practice. The bronze that was once allotted to the sculpture was reassigned for making cannons, and the Duke’s commission was dissolved. Da Vinci was reported to have wept on his deathbed for his unfinished masterpiece.
Charles Dent, a retired airline pilot, read about da Vinci’s story in an article in National Geographic in 1977 and conceived the idea to “give Leonardo his horse.” Dent founded the non-profit organization Leonardo da Vinci’s Horse, Inc. (LDVHI) and worked with sculptors, art historians, da Vinci scholars and equine experts to produce a modern version of da Vinci’s dream. The sculpture was unveiled in Milan on September 10, 1999, exactly 500 years from the day da Vinci’s original model was destroyed.
“The whole project is a beautiful concept,” says Peter Homestead, President of Tallix Foundry in Beacon, New York, USA, the art foundry that produced Il Cavallo. “It is a beautiful idea to do a modern interpretation of something the great master, Leonardo da Vinci, never had a chance to see to completion.”
To produce Il Cavallo, Tallix worked from a design by American artist Nina Akamu. Once an 2,4m (8 ft) model was produced, it was put on an enlarging apparatus that mechanically works the 7,3m (24 ft) clay model to scale. Working the entire full size model took one year. Molding and Casting
A “mother mold” of the horse was made by spraying the model with liquid rubber mold material and then applying a half-inch layer of polyester resin and fiberglass to the rubber coating for a sturdy backing. When it hardened, the rubber sections were removed.
Most of the horse was sand casted. Sand casting involves making positive plaster castings from the mother mold and placing them, one at a time, in an eight foot steel molding box. Next, a sand and binder mixture is packed around the section. Once the mixture has hardened, the sides of the molding box are separated and the plaster is removed to create a negative image in the sand. The molding box is closed again and molten bronze (at about 1,093 degrees Celsius, or 2,000 degrees Fahrenheit) is poured in through pour spouts. When the bronze has cooled, the sand mold is broken and the result is the bronze casting.
Lost wax casting was used on the more intricate areas, like the mane, tail and face, to pick up small details. The lost wax casting process starts by coating the rubber molds in wax to make wax replicas of the original model’s parts. The wax parts are dipped into a slurry ceramic shell solution and coated to 1,5cm (5/8 in.), which hardens into a mold. To remove the wax, the mold is placed in an autoclave, baked at 732-788 degrees Celsius (1350-1450 degrees Fahrenheit), and the wax is burned out. Then the mold can be filled with bronze.
The materials used in casting and molding may have changed, but the methods have remained somewhat unchanged since da Vinci’s time. Although Leonardo planned to cast the entire horse in one piece, experts today say that it would have been impossible because bronze is difficult to keep at constant temperature while it flows into the many crevices of a large mold. Tallix’s experience in large metal sculpture dictated casting the sculpture in 60 pieces, all about four feet square and comprised of 6,2 to 10mm (1/4 to 3/8 in.) thick silicon bronze. Assembly in the Foundry.
The castings were matched up, tack welded together and then MIG welded (GMAW, or wire welded) on the inside of each seam with Deltawelds® and XR-A push-pull wire feeders from Miller Electric Mfg. Co. Tallix chose the XR-A because it could reach the most difficult places within Il Cavallo, sometimes up to 9m (30 ft) from the power source.
Tallix welders used 1,2mm (.045 in.) diameter silicon bronze wire (ERCuSi-A per AWS/SFA A5.7) at traveling speeds of 152cm (60 in.) per minute.
“I’ll bet we used 500 to 600 pounds (225 to 270 kg) of wire, with a total of about one mile (1,6km) of welds,” Homestead says.
TIG welding (GTAW) was used on the external sides of the seams where cosmetics were more important. TIG gives a more attractive weld because it produces less spatter and doesn’t warp or distort the metal. Tallix used Miller Syncrowave® 250 TIG machines and 1,4 to 2,4mm (1/16 to 3/32 in.) diameter silicon bronze (ERCuSi-A per AWS/SFA A5.7) filler metal rods.
The welds were finished by a process called chasing, which blends the welds to the “rough rake” texture of the sculpture and prepares the surface for the patina (the chemical that colors the bronze) and wax.
A structural engineer analyzed the sculpture and set structural specifications based on loads from natural forces like wind and earthquakes, as well as the structure’s own weight load. From those specifications, an armature of 304 type stainless steel was designed to support the sculpture from the inside. The 7,6cm (3 in.) diameter armature tubing was plasma cut to created a “ribbing” that fit the exact curves and dimensions of the horse. To MIG weld the armature to the bronze skin, Tallix used 1,2mm (.045 in.) diameter ERCuAl-A2 aluminum bronze wire.
The two legs on which the sculpture rests were each fitted with a 20,3cm (8 in.) diameter, 2,5cm (1 in.) thick stainless steel/titanium pole that extends 45,7cm (18 in.) below the hooves and gets MIG welded to steel match plates embedded in the concrete pedestal in Milan. The poles reinforce the 13,7 metric tons (15 tons) of weight put on two legs (11 metric tons/12 tons from the bronze skin, 2,7metric tons/3 tons from the armature).
Once the sculpture was completed, it was unbolted at the seams connecting the seven main parts (head/neck, body, four legs and tail) and flown to Milan for final assembly in the Hippodrome’s Cultural Park. Three welders, a finisher and a patina worker from Tallix traveled to Milan to begin the one week assembly on Il Cavallo.
When they arrived, two Syncrowave 250’s and a Deltaweld 602 with XR-A push-pull wire feeder were waiting for them, courtesy of Miller Europe, which has facilities in Milan.
“We trust Miller products and we wanted to be sure we were getting the same quality and performance in Milan that we had in the foundry, so we requested the same models we had at home,” Homestead says. “And the Miller people in Milan were very good to us. They made sure we had all the ceramic cups, tungsten electrodes and wire we needed.”
Dr. Antonio Susta, sales and marketing manager for Miller Europe, realized the historic significance and grand scale of the project and wanted to be sure that the Miller equipment helped keep the project moving.
“Tallix workers had a very tight schedule and they couldn’t have any last minute problems with their welding machines,” Susta says. Assembly in Milan.
To assemble the sculpture, the horse’s body was set on its side and the four legs were bolted and then welded on. Next, the body and legs were lifted by a crane, placed upright and set on the concrete pedestal.
The head and tail were lifted by crane, positioned and bolted on from the inside before being welded onto the body. Another stainless/titanium pole reinforced the tail. Once all inside welding was completed, the trapdoor on the horse’s belly was welded shut and finished. To complete the project, the pedestal received a white marble facade.
Tallix uses Miller welding equipment because it provides the quality and reliability that helped make it the foundry LDVHI trusted to work on such a monumental project.
“Any successful business needs a good business plan. You need good people to do the work and good equipment to assist the people,” says Homestead. “Miller certainly fits into Tallix’s plan.”
Since its unveiling, Il Cavallo has received notice from people all over the world, including travelers, families and school children. To everyone involved in the making of Il Cavallo, including the artists, the LDVHI board and the Tallix crew, it is much more than just a sculpture.
“In the future, our culture will be studied through the sculptures and artifacts we produce today,” Homestead says, “just as cultures have been studied by their art throughout history.”
Information courtesy of Miller Electric