Pencil in, or ink in?

Semantics, or the study of meaning in language (single word or entire texts), can be quite telling. For example, the phrase "pencil in" denotes "to note or arrange provisionally or tentatively", whereas the saying "ink in" stands for "to confirm or arrange definitley". So which of these two expressions would best describe sketching as an ideation tool? Sketching means to draw something that is rough or unfinished, for example, a preliminary drawing*, which may suggest the pencil sketch is the tool for ideas. In contrast, to pen something, or "ink in" (using a ballpoint, felt-tip or fountain pen) indicates something more permanent, as in "to use ink to go over pencil lines in a drawing". Yet both the pencil and the pen are implements used for generating and communicating ideas, not only on paper but also for input on digital devices, such as tablet. What matters, then, is not so much what ideation tool to use but how best articulate first thoughts and ideas, that is, through words, sketching, modelling or computing, or "thinking aloud in sketch mode" irrespective of the tool. * Indeed, in the 17th century, "design" was identified in a professional context as "a preliminary sketch for a work of art: the plan of a building, or part of it."