There is a furnace in the sky, and metals are born on the earth. Huiye is cold and quenched to illuminate the clouds. Qing means that there is a furnace in the sky. Five kinds of metals are born from the earth. After smelting and quenching, they become weapons that can clearly reflect the clouds.
1. Honglu is also called a furnace. Hardware means five metals of different noble and low quality. These five metals are gold, silver, copper, iron, and tin. Huiye is used to make weapons, and cold quenching is used. To cool it down in water, the clouds turn into clouds.
2. "The sky has an oven, the earth produces hardware, and the smelting heat is cold and the clouds are quenched." This sentence comes from the smelting chapter of "Tiangong Kaiwu" written by Song Yingxing of the Ming Dynasty.