FeLion Studios (Fe=Iron / Lion=Leo) is best known for its iron casting and community iron pour events, but there are times where I will elect to cast alloys in the non-ferrous world such as aluminum or bronze. Crazy, right? Though iron is definitely my specialty, it’s worth noting that there are specific times where aluminum or bronze either just make more sense for the event we’re hosting or for the pieces that need to be cast. Let’s take a closer look.

Just the facts, Ma’am

Physically, aluminum + iron have very little in common. With iron being nearly 3 times the weigh of aluminum, it also has a much higher melting point that starts at ~2200°F in comparison to aluminum which melts around at 1,200°F.

Another notable feature is that iron is magnetic while aluminum is not, and to many people’s surprise, iron is a very brittle metal that easily breaks under a little stress whereas aluminum has a much higher ductility (malleability).

Worldwide, aluminum is much more abundant of a metal on this planet, but extracting it from its earthen ore is much more difficult (expensive) than iron, so in the market iron gets a lower value than aluminum, even though the places where it exists naturally a much more selective.

Pieces of cast iron radiators used for iron pours. Image credit: Rob Dutcher 2018

Process, Tools & People

So what do these differences mean from a casting perspective? First, we need to treat each of these alloys completely differently, starting with the equipment we utilize, the tools, and the techniques we either build or employ to work with each metal afterwards.

We melt our iron by stacking coke fuel & scrap iron from bathtubs and radiators into a tube-like “continuous run” furnace called a cupola, ( or sometimes a cupolette if it has a lid). These are hand-made, scaled down designs that artists create in order to effectively manage the melting of iron at without the use of heavy industrial equipment and facilities, but still achieving a casting temperature of at least 2500°F.

The “tube” of the furnace is usually a steel shell that is lined with 2-3 inches of refractory, and has a bunch of specifically located holes formed into it for adequate air pressure that bellows the ignited coke fuel with electric blowers, and more holes for the slag to drip out on one side while the pure molten iron is tapped out from another side.

The coke fuel itself is a purified, highly processed coal-type product that feels like lava rocks but burns at an incredibly high temperature necessary for super-heating raw cast iron. As the coke ignites inside from the forced air of the wind belt, iron begins to rain down from the stacks above, dripping onto and pooling down around the bed of coke, adding much needed carbon to the metallurgical mix during the melting process inside of the furnace. Any impurities in the iron naturally floating to the top and becoming slag, which slowly pulses out of the slag hole in the furnace, while also being pushed away from the stream of iron flowing into molds during casting.

When we run our cupola, it requires months of prep work from volunteers & artists to get all of the fuel and iron material charges processed into the right size so that our furnace can efficiently melt it, which is typically braking the iron into nacho-chip sized pieces, and the coke fuel into lemon-sized chunks. We also need several ladles for multiple teams of artists to catch the iron as it continuously melts around 100lbs of iron every 6-8 minutes for 5-7 hours straight during the pour, steel tools for working the furnace, large benches and dozens of pallets for keeping the sand molds off the ground, and at least 20 skilled artisans on board to delegate different roles to while the furnace is screaming hot and making (literally) tons of metal. We generally will melt between 1800 lbs to 3500 lbs of iron during each iron pour, so the more people, the merrier!

FeLion Studios’ furnace “FLO”, when she was just a wee cupolette.

The furnaces used for Aluminum (and bronze) are much simpler in some ways, as needing specialty coke fuel to ignite the metal and hand-breaking scrap iron for a material source just isn’t necessary. An aluminum furnace is typically a gas-fueled, refractory lined furnace (Liquid Propane or natural gas) that runs as more of a “batch” process versus the continuous flow of an iron furnace. We load a crucible (a refractory-type bucket if you will), with the raw metal and then just turn on a gas burner and small air blower, and wait for it to melt.

This style of furnace allows for a lot more control and a somewhat more relaxed experience while melting. It also doesn’t require the large amount of labor needed in order to prep before a pour. In fact, melting & pouring aluminum can easily be achieved with just 1 person if you are organized, but it’s much more fun with a few solid friends around :}

Aluminum melts quickly, it’s light, easy to move, and is typically bought in pre-made ingots sizeable for the smaller crucibles that we use. Our aluminum crucibles melt and hold between 10lb and 50 lbs at a time, as compared to the 80-120lb iron ladles we need for even a “small” cupola pour. Additionally, you don’t need as much aluminum weight to fill the same volume of molds as we would in an iron pour, because aluminum is just that much lighter than iron.

Dan Dricken lighting his aluminum “road show” furnace during one of FeLion’s pours.
Photo Credit: Rona Neri, 2022.

Artistic Results

So what do these differences all mean in terms of artist potential? The short answer is “it depends on what you are casting, and how you make your mold!”. If we are just looking at the “open faced” sand molds that are popular at the community events we host, there are similarities in the level of detail achieved for each person’s mold, but the physical properties are so radically different, that it can really change the final look and feel of your casting, even if they were duplicate designs side by side.

The most notable is going to be the weight difference, but there’s also the magnetic properties to consider for the way they would finally display, as well as the way each metal oxidizes.

Obviously, iron will rust within even high humidity, but aluminum just kind of stays a stable silver hue no matter how soaked it gets. Each metal has different patination potentials as well: iron can really change in color from black to bright orange, purple, red or blue using everything from salt water, to acid, cooking oil, heat, wax or even different herb mixtures. Whereas aluminum doesn’t’ really respond visually to heat the same way iron does, so it requires more topical, cold application solutions such as tints, paints, acids and buffing tools to achieve different colors or levels of shine.

Now, if we are to look at a little more complex mold making and 3D forms, this is where things get really interesting in the casting outcomes and differences between the 2 metals. First, because iron requires so much energy to become molten, it typically solidifies a lot “faster” than aluminum in a mold, and this can cause some loss of finer details if your iron isn’t poured hot enough, or your fast enough, or utilizing correct gating and venting to make sure the metal can efficiently get to your part inside.

Alternatively, aluminum tends to stay molten for a lot “longer”, thanks to its lower melting point, which can sometimes benefit castings with very thin details, as the metal stays liquid long enough to reach into those tiny crevices before chilling off. However, if there isn’t enough pressure in the mold to push the lightweight metal to those parts, there can still be some miscasts.

The result pf potentially thinner castings can make it seem as if aluminum allows for better details, but in reality, it’s all about the way the mold is gated, made, and poured for the fine details to successfully reveal themselves. There’s a significant amount of engineering & science that goes into figuring out the optimal metal flow pressure, how to reduce turbulence, provide adequate venting and make sure the metal doesn’t shrink so badly in thicker areas that it causes blemishes. That’s why it takes years, or a full lifetime, to really master the foundry arts trade, as each unique design comes with its own set of technical challenges.

That said, it’s smart to start small with custom projects and eventually work larger over time once you get a few things figured out. I really enjoy seeing all of the wild ideas made during our community metal casting events over the years, and I have been honored to help aspiring artists grow their body of work into much more complex and intriguing pieces as they learn the multiple steps of the pattern making, mold design and the entire metal casting process.

Aluminum X Iron - What's the big diff?

Just the facts, Ma’am

Process, Tools & People

Artistic Results