He tested a number of old brushes to compare the composition of their hairs with the characteristics of modern brushes, and has developed a wide range of writing brushes for specific purposes.
李志仁試了五次，總算仿造出一枝天平筆，興沖沖地拿去給老師看。老師滿意地點點頭，又取了一個晚輩由非洲帶回來的葫蘆，囑咐他以葫蘆為筆桿做一枝聯筆。這回李志仁輕而易舉地做出來了。慕老十分高興，頻加稱讚，李志仁因此對自己做筆的信心大增。