The Automatic Pig Casting Machine: Edward Uehling’s Sloss Patent
October 15, 2026
Sloss Furnaces did not adopt the technology until 1931
Long before Sloss Furnaces fully mechanized its pig-iron casting operation, Edward Uehling patented an automatic pig casting machine, October 15, 1895, while working at Sloss. Although the invention promised to transform one of the ironworks’ most demanding processes, Sloss did not adopt the machine until 1931. Its eventual installation marked a major shift away from traditional sand casting and toward a faster, more efficient method of producing pig iron.
Moving Molten Iron to the Casting Machine
The process began at the blast furnace, where molten iron flowed through a curved trough into large ladle cars. Also known as bull ladles because of their great size, these cars transported the molten iron from the casting shed to the pig casting machine.
Once the ladle car reached the machine, its “belly” tilted, allowing the molten iron to pour into an endless train of individual pig molds. The molds were carried along by a chain drive, creating a continuous casting process that required far less manual labor than earlier methods.
From Molten Iron to Finished Pigs
As the molds traveled up an incline, the iron cooled and solidified into small bars known as pigs. Each finished pig weighed approximately 45 to 50 pounds. When the molds reached the top of the incline, the pigs were shaken loose and dumped into waiting rail cars. Workers then sprayed the pigs with water to remove some of their remaining heat and accelerate the cooling process. This made the freshly cast iron safer for transport, while also reducing the intense heat radiating from the loaded cars.
This modern technique completely eliminated sand casting at Sloss Furnaces. Instead of pouring molten iron into temporary sand molds and removing each casting individually, workers could produce a steady stream of uniform pig iron bars through a mechanical system.
The Workers Behind the Process
Although the automatic pig casting machine dramatically modernized iron production and reduced the need for traditional sand casting, it still depended on a specialized, highly coordinated workforce to manage the intense heat, liquid metal, and heavy machinery. Jobs associated with the ladle cars and pig casting machine included:
Machine & Ladle Operations
- Ladle Car Operator: Controls the specialized rail cars (ladle cars) that transport molten iron from the blast furnace to the casting machine, carefully tilting them to pour the liquid metal.
- Casting Crew: The core team responsible for operating, monitoring, and maintaining the pig casting machine's conveyor belts and molds.
- Lineman: Monitors and maintains the moving conveyor line, ensuring the chain of molds (molds/pans) moves smoothly without jamming.
Pouring & Metal Management
- Iron Pourer: Regulates the flow of molten iron from the ladle into the runner system that feeds the moving molds.
- Torch Man: Uses a thermal torch to cut away skull (solidified crust) or blockages, ensuring the molten iron flows freely without freezing in the channels.
- Scrapper: Reclaims spilled or excess iron that solidifies outside of the molds, breaking it up to be remelted.
Mold Preparation & Quality Control
- Lime Man: Mixes and applies a lime wash coating to the empty iron molds. This prevents the molten iron from sticking to the molds, allowing the cooled "pigs" to drop out easily.
- Casting Foreman: The supervisor who oversees the entire operation, managing safety, production speed, and crew coordination.
Traditional Foundry Roles (Support & Low-Volume Work)
Even with an automatic machine, traditional foundry workers remained essential for custom jobs, replacement parts, or maintenance:
- Molder: Prepares the sand molds for specialized castings that cannot be run on the automatic machine.
- Pattern Maker: A highly skilled artisan who carves the wooden or metal replica (pattern) used by the molder to create the sand impressions.
Sloss Adopts the Machine in 1931
Sloss finally fully mechanized its pig-iron casting operation in 1931, when it installed two 125-ton mixing ladles along with the pig casting machine. The installation represented an important advancement in the plant’s production system and demonstrated how Uehling’s patented concept could be integrated into large-scale ironmaking.
The machine remained part of Sloss’s industrial history for decades. In 1975, it was dismantled, and most of its components were sold to the American Cast Iron Pipe Company.
A Lasting Industrial Legacy
The automatic pig casting machine connected invention, transportation, and production in one continuous operation. From the furnace trough to the ladle cars, from the tilting “belly” to the chain-driven molds, every stage was designed to keep molten iron moving efficiently until the finished pigs were ready for shipment.
Edward Uehling’s patent, followed years later by Sloss’s 1931 installation, illustrates the gradual evolution of iron production at the furnaces. The machine’s removal in 1975 ended its working life at Sloss, but its role in eliminating sand casting and modernizing pig-iron production remains an important part of the site’s industrial story.
Today, Sloss Furnaces operates as a museum, where visitors can explore the remaining structures of the pig-casting pit and see the surviving machinery that reflects Birmingham’s industrial past. Come out to Sloss Furnaces to experience these historic remains firsthand and gain a deeper understanding of how molten iron was once transformed into transportable pig iron.
