Meaning of Calligraphy Phrase "sumi tsugi"

I came across the phrase "sumi tsugi" somewhere (cannot remember where and therefore cannot cite the source). The phrase was in English so I do not know which kanji for "tsugi" would be appropriate, 次 or 継ぎ. Thus my question: Does this phrase refer to dipping the brush into ink a second time while writing one kanji, or does it refer to going back into a completed kanji to correct/finesse a stroke (which I do know is strictly forbidden)?