There is a furnace in the sky, and hardware is born underground. What is cold quenching, clear?

There is a furnace in the sky, and there is hardware in the ground. It is clear that there is a furnace in the sky. Five metals were born in the earth, and after smelting and quenching, they became weapons that can clearly reflect clouds.

1, Lu Hong is also called the stove. Hardware refers to five different metals, namely gold, silver, copper, iron and tin. Huiye is used to make weapons, which are cooled by cold quenching into water, and the clouds are light and the wind is clear.

2. The sentence "There is a stove in the sky, hardware is born underground, and it is bright when it is cold" comes from the Heavenly Palace Metallurgical Chapter in the Ming and Song Dynasties.