かなくそ

か

な

く

そ

Meanings

1

slag; dross

usually written using kana alone

Refers to the waste material left over from smelting or refining metal.

製せい鉄てつ所じょでは、かなくそが大たい量りょうに出でる。
At the steel mill, a large amount of slag is produced.

2

iron rust

usually written using kana alone

Specifically refers to rust from iron; less common than the general term さび.

古ふるい鉄てつの塊かたまりから、かなくそが落おちていた。
Iron rust was falling off the old lump of iron.