KWZ Iron Gall Blue #5 fountain pen ink, 60 mL inside a glass bottle. KWZ fountain pen inks are handmade in Poland by a small team of fellow fountain pen enthusiasts.
See the entire collection of KWZ inks available from Lemur Ink.
Although many users have had no issues with KWZ Iron Gall inks and they have been known to operate completely fine in modern fountain pens (including those with stainless steel nibs), we still urge caution and recommend regular use of the pen, as well as practicing good pen hygiene.
Read KWZ's blog about using their iron gall ink in modern fountain pens.