Sailor Fountain Pen Ink Souboku blue-black (50 ml)

Souboku is Sailor's classic blue-black in pigment formulation – a deep, slightly undersaturated blue-grey black with moderate shading that dries water-resistant on paper and remains archival. Micro-fine pigment particles ensure smooth, slightly wet flow, much like dye-based inks – combined with the permanence of a pigment suspension. Bottled in glass (50 ml), manufactured in Japan.

Features

• Archival and water-resistant: Once dry, Souboku withstands flowing water. Signatures, minutes and archival documents retain their legibility permanently.
• Micro-fine pigment particles: Particle size is chosen so that ink flow through the nib remains nearly like a dye-based ink – no clogging, no skipping when writing.
• Blue-black colour with moderate shading: The tone sits between classic ink blue and dark grey-black. Stub nibs and flex nibs reveal visible shading; fine nibs write in an even, conservative dark tone.
• Quick drying on the paper surface: The ink dries on the paper rather than sinking in completely – an advantage on smooth, calendered paper and especially for mixed-media work with watercolour washes on top.
• Minimal feathering and barely any show-through: Even on lighter copy paper the writing remains clean; on ink-proof paper the result is even more defined.
• 50 ml square glass bottle with sturdy construction – deep enough to fill even short converters with ease.

Use & Tips

• Rinse fountain pen regularly: Pigment inks can dry out if left standing for long periods and crust up the nib. Flush thoroughly with lukewarm water every 4–6 weeks – or before the pen sits unused for extended periods.
• For mixed-media and sketching: Since Souboku dries on the paper surface, it works well as a line base for watercolour washes – lines don't run when water flows over them.
• Nibs and paper: With a medium to broad nib on smooth, calendered paper, Souboku shows its shading most clearly. Fine nibs deliver an evenly dark, readable line – ideal for dense handwriting and longer texts.
• Compatibility: The ink was developed for Sailor fountain pens and works with Sailor converters and cartridges. Also usable in other fountain pen brands with good ink flow and regular use.
• For archival purposes: Archival means the writing is light-resistant and water-resistant – suitable for certificates, contracts and anything that needs to remain legible long-term.

For Calligraphy & Illustration Enthusiasts

Souboku dries on the paper surface rather than sinking in completely – behaviour that can be deliberately exploited on watercolour or textured sketch paper. Those working with stub nibs or flex nibs get Souboku's moderate shading and deep blue-grey black, a tone that reads classically elegant without tipping into pure black. As a pigment ink it's also suited to work where a colour wash or watercolour is laid over the line – the dried line stays stable and doesn't bleed.

Technical Specifications