Kakou Seiboku inkstick ( Bluish black, Deer glue, 鹿膠青墨 )

Kakou Seiboku spells its own recipe into its name: Ka (鹿), deer, Kou (膠), glue, Sei (青), blue, Boku (墨), ink — a bluish-black stick built around a genuinely rare binder.

Deer glue isn't common in inkstick-making, and here it's chosen for how far and how evenly the ink extends across paper, letting a single stroke carry its color to the end without thinning out partway through.

That quality makes it especially well suited to calligraphy, where a long, unbroken line depends on the ink holding steady from first touch to last. It's offered in two sizes — 3 at 25.3×119.8×15.4mm, 65g, and 5 at 31×130.7×19mm, 104g — so both smaller practice sessions and larger, more ambitious pieces can draw on the same rare material.

A quietly technical inkstick from Kobaien's rare-glue family, worth seeking out if you're curious how a single change of binder can shift the way ink moves and settles on the page.