C185 Gunpowder test

After thinking for a long time, he sat there motionlessly like a meditating old monk.

All of a sudden, Chu Yuhan mumbled, "Thread, line, line..." Can I use cotton thread? "

Thinking of this, Chu Yuhan stood up and went outside the door, and said to the soldiers standing guard outside, "Quickly get me some cotton and oil." With that, Chu Yuhan walked back in and closed the door