Regarding blue-black ink, those inks were not dye inks like you'd use in most fountain pens. They were an iron gall ink, which can foul an improperly maintained fountain pen. The iron gall ink goes on blue and as it oxidizes it bonds with the paper and settles into a blacker shade. This is really durable and for a long time in places like the UK, it was the ink legally required for use by registrars for recording legal documents because of its endurance and tampering resistance.

I recently started a new blog (see my link) for having fun exploring sub-$25 fountain pens and other low-cost/high-value stationary supplies.