I have to perform an unusual task - I have to update some texts on an ancient parchment book. I will see the book (an ancient church journal, informal enough but 5 centuries old) in a few days. For more important documents on other more important and precious books a calligrapher is hired but this is a 'modest' journal and traditionally must be updated by a member of the congregation so the professionals are out of the question. I was asked to write on it as the old guys are no longer confident about this and they need someone with a firmer hand (the fools ). Too much time passed since the last time and they cannot remember which ink was used the last time, but it was something tragically normal and commercially available.
I will use a modern FP (a Pelikan or a Montblanc or a Lamy, as for the latter I have calligraphy nibs if needed, I will see ) and I have some modern inks (Pilot, Diamine, Aurora, Pelikan, Montblanc) but I need something with good permanence (the book is centuries old and in excellent condition for its age and maybe good for another half millennia - I find this a little discomforting) but I was planning to use DIamine Registrar's as an ink with the correct combination of colour, permanence and good behaviour - all this in theory. I never used this ink on real parchment, only on modern papers. Any previous experience? Any suggestion? Thanks for any idea/exchange of experience on this unusual topic.