Ink makers are careful to select high-quality glues, which produce a lustrous ink that is thick without being tacky and doesn't inhibit the motion of a brush. They give still more care to the ratio of glue to pine soot. If too much glue is used, the calligrapher's brush will drag. If there is too little, the ink will lack luster.
牛皮膠是由進口牛皮熬成的工業用膠，由於是動物性膠質，品質不佳很容易發臭，如果能選用上等牛皮膠，墨質就會濃而不黏稠，運筆時不會拖尾，而且墨色發亮；膠和松煙的比例更需拿捏，膠如果過重會影響運筆的流暢度，如果不足呢，寫出來的字又少了光彩。