He washed his writing brushes in a pool and the pool turned black.

他在水池里洗了笔，水池变黑了。

Tools and materials involve writing brushes, ink, colored ink, rice paper and silk.

工具和材料包括书写笔，墨水，彩色墨水，宣纸和丝绸。

Proper technique for handling the writing brushes and maintaining the proper angle between the tips of brushes and the paper are required.

处理毛笔和保持笔尖与纸张之间适当角度的正确技术是必需的。