24-04-2026, 11:44 AM
I'm slightly confused. In the interest of actually aiding in this conversation, answers to the following would be helpful:
-Is there a certain way IGI should or should not get absorbed/ bleed through the parchment?
-Is it normal that IGI soaks through to the other side of a sheet of parchment, should it only happen in certain circumstances (such as excess moisture)?
-Should IGI rub off onto pages it is facing once dry?
-When IGI soaks into the vellum, is it really "dissolved", or is it the same chemical structure within a porous material? (like water in a sponge is not dissolved)
If we know the answers to these we can potentially test some hypotheses using image analysis of different pages.
The crux of the issue here is that we have two different studies now with two wildly different ranges for the transparency of their specific IGI. In that second study, it says "nearly transparent in 900-1500nm". Your images clearly also do not show fully transparent IGI, even at 940nm; some of it is still visible. Therefore our observations on the VMS ink is consistent with it appearing "nearly transparent" at 900-1500nm.
Furthermore, the existence of two ranges in two studies implies the possibility of more ranges for more types of IGI in others. The exact composition of the ink clearly matters in this regard.
-Is there a certain way IGI should or should not get absorbed/ bleed through the parchment?
-Is it normal that IGI soaks through to the other side of a sheet of parchment, should it only happen in certain circumstances (such as excess moisture)?
-Should IGI rub off onto pages it is facing once dry?
-When IGI soaks into the vellum, is it really "dissolved", or is it the same chemical structure within a porous material? (like water in a sponge is not dissolved)
If we know the answers to these we can potentially test some hypotheses using image analysis of different pages.
(24-04-2026, 03:05 AM)Jorge_Stolfi wrote: You are not allowed to view links. Register or Login to view.(23-04-2026, 09:57 PM)oshfdk wrote: You are not allowed to view links. Register or Login to view.The following article shows iron gall ink as nearly transparent in 900-1500nm: ... Quoting from the article:
Quote:The underdrawing materials that become transparent, and are not therefore visible, include red Conte crayon, charcoal and iron gall ink.
Yes, but that is what the article I quoted said too: iron-gall ink remains opaque up to 1200 nm, while ocher becomes transparent by 800 nm. And the VMS ink is already transparent before 940 nm (the longest wavelength used in those images).
All the best, --stolfi
The crux of the issue here is that we have two different studies now with two wildly different ranges for the transparency of their specific IGI. In that second study, it says "nearly transparent in 900-1500nm". Your images clearly also do not show fully transparent IGI, even at 940nm; some of it is still visible. Therefore our observations on the VMS ink is consistent with it appearing "nearly transparent" at 900-1500nm.
Furthermore, the existence of two ranges in two studies implies the possibility of more ranges for more types of IGI in others. The exact composition of the ink clearly matters in this regard.