I started to melt some Cast Iron today

[Hawkeye]

I learned about white iron when I picked up a cast weight at the scrappers. About a foot long and just over 2" square. The first thing it did was eat a 10' bandsaw blade. The shaper liked it fine, but it was a bear to machine otherwise.

After I read about white iron, it made sense. When the foundry has iron left over at the end of a pour, they can pour it into molds for things like weights that don't matter. Then, they're more likely to chill it fast to get the mold empty. The result is white iron. Fine for weights, scary for raw material.