This is a gorgeous blue-black fountain pen ink from TWSBI.
This ink is water resistant.
TWSBI is Inspired By Writing! Originally an OEM manufacturer for different brands, Ta Shin Precision decided to sell under their own brand, and TWSBI was born. TWSBI's name is stands for the Hall of Three Cultures and is made up from a combination of words (San Wen Tong and Bi). TWSBI has a wonderful mission statement: To inspire and recapture the romanticism of art and literature…starting with the pen.