What qualities make Pilot Iroshizuku Shin-Kai my favorite fountain pen ink? It is one of the very few inks that works in any pen with any nib on any paper and in any situation. Plus, it is blue black, which I have a well known affinity for. I never hesitate to use it, which is not something that can be said about every ink I own.
Shin-Kai translates into "Deep Sea" and I would say that is pretty accurate. It is the perfect combination of blue and black with no stray colors you see in other blue black inks like green, teal, purple, or grey. It does have a slight red sheen on wetter lines, which is a nice touch. In the pantheon of blue black inks I have tested it falls smack in the middle in darkness. There are lighter and darker blue blacks to be found.
The Pilot Iroshizuku line is notoriously well behaved. It works with any size nib, from extra fine and firm like my Pilot Custom Heritage 912 PO nib to 1.5 mm stub nibs. It is also easy to clean, leaving no trace behind in any pen or converter I have used.
If there is a knock on Shin-Kai - or any Iroshizuku ink - is that it is not waterproof. It will run or fade if it gets wet so if that is high on your ink requirments list you may want to look elswhere. For me, it is not a consideration at all for the type of writing I do so its not a negative on my list. Other than that it is flawless in my mind.
You have one ink that can be your favorite. Just one - no hedging your bets. What is it?
(JetPens is an advertiser on The Pen Addict and I received this product at no charge.)