00:00Think these workers are drawing a magic circle in the dirt?
00:02They're actually making a cast iron fence panel from scratch.
00:05This technique is called open-face sand casting.
00:08Workers melt pig iron and scrap steel into molten iron at nearly 2,550 degras.
00:13Meanwhile, they pack special molding sand into a flat bed,
00:16then press in a reusable pattern to form the fence design, pouring channels and vents.
00:21Once the pattern is removed, several workers lift a ladle and slowly pour in the glowing metal.
00:26The iron runs through the grooves like it's tracing the design by itself.
00:30Filling every curve before it can cool and harden.
00:32But why doesn't metal this hot stick to the sand?
00:35Because this isn't ordinary river sand.
00:37It's mostly heat-resistant silica sand mixed with bentonite clay and a little water.
00:41The silica withstands the heat, while the clay binds the grains tightly enough to hold the shape.
00:46Foundries may also add graphite powder or a refractory coating to reduce burned-on sand.
00:50After the iron cools, workers break apart the one-use mold and remove the rough casting.
00:54They cut off the leftover gates, grind away sharp edges, and apply a rust-resistant coating.
00:59What looked like a pile of dirt has basically worked like a giant metal 3D printer.
01:03OrCHESTRA
01:03Here we go.
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