Does anyone know ...

[Silverbreeze]

If MontBlanc ink is Letex sac safe?

Or should I reserve them for my Cartridge Convertor pens??

[mhosea]

I've never heard that it wasn't from anyone, and you'll find that royal blue is super easy to flush out. Irish green is more work, but here again, as far as I am aware, it has never been accused of damaging latex...or anything except maybe a shirt.

[Silverbreeze]

I've never heard that it wasn't from anyone, and you'll find that royal blue is super easy to flush out. Irish green is more work, but here again, as far as I am aware, it has never been accused of damaging latex...or anything except maybe a shirt.

Yeah I am at the point where I am starting to assume all inks make by pen makers is probably safe. Other then Noodler's that's a special case

[mhosea]

Yeah I am at the point where I am starting to assume all inks make by pen makers is probably safe.

This is the working assumption of many. Proving anything is hard, apparently, so we have to make judgment calls. Historically, however, even pen makers did not always produce "safe" inks. Parker's "superchrome" ink was a case in point. Basically they made their main pen of the day safe for the ink rather than made the ink safe for pens in general.

[kataish]

You already have an answer, but I have used Montblanc ink in my latex sac pens, and its fine. I generally stick to anything but Noodler's and Private Reserve (and iron gall) in sac pens. I know there are other "boutique" inks that people are worried about (Diamine, for one), but they have been making ink for A VERY LONG TIME and I trust them. If they made ink that was shit for latex sac pens, they wouldn't be in business because MOST pens were sac pens in the 30s-60s (ish). :)