What does the は in this sentence do?

Question

力任せに壁面に罅{ひび}を刻んでは一つ、また一つと体のパーツを外気に晒{さら}していく。

What does は do here? Is it contrasting?

Thanks!

Answer 1

[V1] + ては + [V2] or [V1] + では + [V2] is a fixed expression that describes two actions (V1, V2) are repeatedly happening in rapid succession.

See ては definition 3:

３ 二つの動作・作用などが対になって繰り返される意を表す。「幼い頃は電車を見ては喜んでいた」「姉はいつも洋服を脱いでは着て楽しんでいる」

So this sentence means that someone is repeating the two actions (壁面に罅【ひび】を刻む and パーツを外気に晒【さら】す) again and again.