Assertion: iron gall ink | /r/ObjectUse | used in fountain pens
Facets:
Source sentences:
text: Iron gall ink was used in fountain pens when they were invented but has the disadvantage of causing corrosion to metal parts.
text: Though not in mainstream 21st-century use like dye-based fountain pen inks, modern iron gall inks are still used in fountain pens where permanence is required.