I enjoy the Noodlers inks that are bulletproof (or as bulletproof as their black, Heart of Darkness, Liberty's Elysium, etc). All those inks work well in my various pens.

Looking to expand my inks, are there other brands that make claims of "bulletproof" qualities?

In my search I find many ink qualities listed, but none seem to outright say "bulletproof" or other claims of longevity.

What inks should I consider adding to my stock?

Thanks.

Sg