Cast iron

Cast iron is an iron material with 2 to 4 percent carbon that is poured into molds in a liquid state rather than forged, and it is used to make pans, roasters, and grill plates that absorb heat and last a long time.

Cast iron is an iron material containing 2 to 4 percent carbon; it is poured into molds in a liquid state rather than forged, and is used to create pans, roasting dishes, and grill plates that absorb heat and retain it for a long time.

The carbon within it is not dissolved invisibly; for the most part, it exists as graphite in tiny crystals. The foundry industry classifies cast iron according to the shape of this graphite: in thin flakes, in worm-like curved shapes, or in small spheres. The most common variety is gray cast iron (flake graphite cast iron), and because its fracture surface appears gray, it is also known as "Grauguss." Standards regulate which variety is which: DIN EN 1561 for gray cast iron, and DIN EN 1563 for ductile (spheroidal) cast iron.

What is the difference between iron and cast iron?

You rarely encounter pure iron in the kitchen. As a material, it is used almost exclusively as an alloy, and its most important partner is carbon. Pig iron, which comes from the blast furnace with 2 to 6 percent carbon, is very hard and brittle after cooling. If the carbon content is reduced to below 2.06 percent, steel is formed; if it remains above that, it becomes cast iron.

Both are heavy. One cubic centimeter of cast iron weighs 7.2 grams, cast steel 7.85 grams, whereas aluminum weighs only 2.7. That is why a cast iron pan feels so substantial in the hand, and why it stays hot once heated, even when a cold steak is placed onto it.

What is the difference between steel and cast iron?

The graphite. Steel, with up to about 2 percent carbon, contains no graphite crystals in its finished state; it is tough and can be rolled and forged. In cast iron, however, the graphite crystals interrupt the microstructure. This costs toughness but provides other benefits: cast iron is easy to cast, dampens vibrations, and requires less energy to melt than steel. The basic structure in between corresponds to that of steel: cast iron is steel with embedded graphite.

You notice the difference immediately at the grill. Big Green Egg, the manufacturer of the ceramic grill of the same name, produces cast iron grates alongside stainless steel ones and describes both honestly: cast iron absorbs heat quickly and releases it evenly, does not warp even under high heat and long cooking times, and sears marks into the meat. Ingredients stick less to stainless steel, which is why delicate fish belongs there.

What is the difference between cast iron and wrought iron?

Wrought iron is, as the Duden dictionary concisely puts it, forgeable iron, whereas cast iron is not. This is due to the carbon: with a high content, the iron does not gradually soften when heated but becomes suddenly liquid, at which point it can be neither forged nor welded. In a bloomery furnace, a lump of forgeable iron interspersed with slag was created, which the blacksmith then cleaned by heating and hammering. Only when furnaces became hotter did the iron flow, and the liquid pig iron became either steel—by burning out the carbon—or, when poured into a mold, cast iron.

This also explains where you find both. A wrought iron railing is forged, often artfully; a cast iron roasting dish is cast and comes out of the mold almost finished, without anyone needing to reshape it afterward.

What are the disadvantages of cast iron?

Three, and all three are manageable. Weight is the first: at 7.2 grams per cubic centimeter, cast iron is almost three times as heavy as aluminum. The second is brittleness. The thin graphite flakes in gray cast iron act like internal notches where stress accumulates, which is why a piece can break if dropped. Ductile cast iron is exempt from this, as the round crystals do not cause notches. Big Green Egg advises always using the grate lifter to insert the cast iron grate so that it doesn't fall in the first place.

The third disadvantage is rust, and this only applies to cast iron without enamel or a coating. Raw cast iron does not like moisture or dish soap, the scent of which it can even absorb. Enameled cast iron does not rust and does not absorb flavors; the pot and lid can go into the dishwater. That is the trade-off: the enamel takes the maintenance off your hands, while the raw iron gradually absorbs the aromas of what has been cooked in it.

Seasoning, drying, oiling

Raw cast iron is protected by a layer of baked-on oil. Ooni pans come pre-oiled and seasoned, and the manufacturer openly states that they must be re-oiled and seasoned throughout their life. Big Green Egg describes it as follows: leave the grate in the closed grill at 180 to 200 °C for one hour, then rub it well with vegetable oil, such as peanut oil, and repeat for another hour at the same temperature. This creates a natural non-stick layer, which also keeps rust away.

In everyday use, less is sufficient. Wash the pan by hand once it has cooled down, using only warm water, dry it thoroughly, and rub it with a thin layer of oil. Never store it away wet. And if rust should ever appear, nothing is lost. Big Green Egg advises: heat the grill to 250 °C, scrub the cast iron clean with a wire brush, put it in the heat for ten minutes, then grease it and return it for 30 minutes. Enameled roasters like those from Le Creuset benefit from consistent, low to medium heat.

When frying, the rule of the material applies: place the meat in the hot pan and leave it there, because flipping it too early risks it sticking. Then take the pan directly to the table on a trivet, sprinkle a few flakes of fleur de sel over it, and the steak will still be warm for the second helping.

Cast iron pans, plates, and roasting dishes

From Ooni comes the round cast iron skillet with a removable handle that fits in the pizza oven, on the grill, or in the oven, plus the Sizzler and Grizzler serving pans, sized for the Ooni pizza oven, in which meat, seafood, or vegetables can be cooked and served immediately. The cast iron grill plate from Big Green Egg has a ridged side for searing and a smooth side for pancakes and eggs. For braising, the enameled roasting dishes from Le Creuset are ready, distributing heat from the base up into the walls.

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