f17r

[oshfdk]

I am not sure I understand the question, or what difference it would make. 

Writing in a black sharpie on black paper would be largely invisible, this doesn't mean that the sharpie became transparent. I was suggesting that maybe in IR the parchment itself has about the same shade as the ink, which would make the ink blend in with the parchment.

However, looking at the page the ink is nearly invisible not only over the blank vellum, but also over the plant image see through from the reverse of the page, so I think it is indeed quite transparent in IR. I don't know what this means in practice, but if this is inconsistent with iron gall ink, this would be interesting.