Pilot Iroshizuku Tsuki-yo (月夜) — Deep Blue-Black, Red Sheen Fountain Pen Ink (50ml)

Pilot Iroshizuku Tsuki-yo (月夜) — Deep Blue-Black, Red Sheen Fountain Pen Ink (50ml)

Pilot Iroshizuku Tsuki-yo (月夜 — literally moonlit night) is a 50ml fountain pen ink from Pilot's Iroshizuku collection — Japan's most iconic premium ink series, formulated in-house by Pilot and bottled in the distinctive flat-sided glass flask that has become one of the most recognisable objects in fountain pen culture. Tsuki-yo draws its name and colour from the particular quality of a night illuminated by moonlight: a deep, professional blue-black with a subtle teal undertone — the specific blue of a dark sky where cool green light softens pure black into something more luminous and alive. It is accompanied by a quiet red sheen that surfaces under the right conditions — a warm, copper-tinged or magenta-red flash at stroke edges and pooling points on premium papers — and a medium shading that gives writing genuine tonal depth. Tsuki-yo is a dye-based ink with no shimmer particles; its visual character comes entirely from colour, shading, and sheen.

The Iroshizuku series was conceived as a celebration of Japanese nature and landscape — each ink named for a plant, flower, or natural phenomenon, each colour formulated to translate that reference into something precise and vivid on the page. Tsuki-yo is among the series' most enduring entries: consistently praised as one of the finest blue-black inks available, and widely regarded as a benchmark daily ink — elegant enough to feel considered, practical enough for serious everyday writing. The bottle is 50ml glass.

Available at Shosai (shosai.ca) in Gatineau / Ottawa — with in-store pickup (J9J 0K6) and Canada-wide shipping.

What Makes Iroshizuku Tsuki-yo Different

The blue-black colour space is one of the most competitive in fountain pen inks — a category where dozens of inks compete on professionalism, legibility, and depth. What distinguishes Tsuki-yo within that space is the teal undertone. Most blue-blacks lean either cool-neutral or warm-grey in their dark register; Tsuki-yo leans subtly green — a dark teal blue that reads as fully professional and high-contrast on the page, while carrying a quiet chromatic complexity that separates it from flat, characterless blue-blacks. Wet, it presents as a rich blue-black with visible depth; dry, it settles into a deep teal-blue that suggests moonlight on a dark sky — precise enough for office use, distinctive enough to be immediately recognisable as something more considered than a standard corporate ink.

The red sheen is Tsuki-yo's secondary signature. It is not a dramatic sheener in the manner of inks formulated specifically for sheen — it is a quiet, warm red or copper-magenta flash that appears at stroke edges, pooling points, and across swab surfaces on smooth, slow-absorbing papers (Tomoe River, Rhodia, Cosmo Air Light). Reviewers describe it as a pleasing complement to the deep blue-black base — unexpected, elegant, and genuinely beautiful in good light. Combined with the medium shading, it gives Tsuki-yo a layered visual character that rewards attention without demanding it.

Colour Profile

Colour

Pilot Iroshizuku Tsuki-yo (月夜) is a deep, professional blue-black with a subtle teal — blue-green — undertone. In the bottle, it presents as a rich, dark blue-black with visible depth and cool chromatic complexity. On the page, it dries to a deep teal-blue: darker and more purely blue-black in fine hairlines and light coverage; slightly lighter and more distinctly teal at broader nib sizes and heavier coverage, where the green undertone becomes perceptible. The colour is high-contrast and fully legible at all nib sizes — professional in weight and seriousness, distinctive in its subtle teal depth. Reviewers describe the base as deep blue-black, dark teal blue, blue-black with green undertone, and one of the best blue-blacks available — a colour that reads as both authoritative and refined.

Shading

Medium, expressive, and clearly present. Tsuki-yo shades with a well-defined tonal gradient that transitions from a deeper, richer blue-black in fine strokes and light coverage to a slightly lighter, more teal-inflected tone at pooling points and broader stroke widths. The shading is not the primary visual event of the ink — the colour depth and red sheen share that attention — but it is clearly visible at medium to broad nib sizes on quality papers, and reviewers consistently describe it as lovely and well-expressed for a dark ink. On Tomoe River and Cosmo Air Light, with medium to broad nibs, the full shading range is most apparent and most rewarding. Fine nibs reduce shading visibility but the colour remains fully expressive.

Sheen

Subtle red / copper-magenta sheen, present and highly appreciated. Tsuki-yo's sheen is its most surprising characteristic — a warm red, copper, or magenta-red flash that appears at stroke edges, pooling points, and across swab surfaces when the ink dries in sufficient quantity on smooth, slow-absorbing paper. It is not a dominant or aggressive sheen effect; in everyday fine-nib writing on standard paper it may be largely invisible. But on premium papers (Tomoe River, Rhodia, Cosmo Air Light) with broader nibs or in large swab coverage, the red sheen is clearly and beautifully present — a warm complement to the cool deep blue-black base that adds unexpected depth and elegance to the ink's character. Reviewers describe it as pretty good red sheen, a lovely magenta sheen, and a quietly spectacular secondary effect. No shimmer; the red effect is entirely sheen.

Ink Properties at a Glance

Flow

Very wet, smooth, and well-lubricated — among the wetter inks in the Iroshizuku line. Tsuki-yo flows freely and generously across a wide range of nib types and pen bodies, making it a particularly comfortable ink for extended writing sessions. The generous flow contributes to the ink's shading behaviour and ensures consistent colour saturation across nib sizes.

Dry Time

Relatively fast — approximately 15 to 30 seconds on quality papers. Tsuki-yo dries quickly enough for practical everyday use without smearing, while still allowing the full colour saturation and sheen to develop at pooling points.

Water Resistance

Low. Tsuki-yo is a water-based dye ink with no meaningful water resistance. It will run or fade when exposed to moisture and is not suitable for documents requiring archival longevity or water-resistant permanence.

Feathering and Bleed-Through

Minimal on quality papers (Rhodia, Tomoe River, Clairefontaine, Cosmo Air Light, Midori MD, Leuchtturm1917). Well-behaved and clean on fountain-pen-friendly papers. Some feathering and show-through may occur on standard copy paper or highly absorbent surfaces.

How to Get the Most Out of Iroshizuku Tsuki-yo

Recommended Paper

Tsuki-yo rewards smooth, slow-absorbing papers that allow the deep blue-black saturation, medium shading gradient, and red sheen to develop fully together:

• Tomoe River (52gsm or 68gsm) — the premier recommendation for showcasing Tsuki-yo's red sheen and full shading range; the slow absorption and smooth surface allow the sheen to develop at maximum intensity at stroke edges and pooling points; the deep teal-blue base reads with full chromatic depth; the semi-transparent surface showcases the ink's layered visual character beautifully
• Cosmo Air Light (Yamamoto Paper) — an excellent surface for Tsuki-yo's sheen expression; the ultra-smooth, slow-absorbing paper allows the red sheen to develop clearly; the deep blue-black reads with full saturation and the shading gradient is cleanly expressed
• Rhodia / Clairefontaine — consistent, reliable, practical; full blue-black saturation clearly expressed; shading visible at broader nib sizes; red sheen present in good light; a strong everyday option that brings out Tsuki-yo's professional character
• Midori MD Paper — smooth, reliable performance; full colour development; shading expression good at medium to broad nib sizes; a practical everyday pairing
• Leuchtturm1917 — good overall performance; full blue-black saturation; shading visible; the cool teal depth reads particularly well against cream-toned pages

Avoid highly absorbent papers. Fast-absorbing surfaces will suppress both shading and sheen, reducing Tsuki-yo's layered character to a clean but flat blue-black.

Recommended Nibs

• Medium to Broad nibs — the primary recommendation for full colour, shading, and sheen expression; more ink on the page activates the tonal gradient and gives the red sheen sufficient surface area to develop; the teal undertone becomes more perceptible and more beautiful at broader coverage
• Stub or Italic nibs — the variation between thick and thin strokes showcases the shading gradient and red sheen most dramatically; the contrast between deep blue-black hairlines and warm red-sheening pooling points is Tsuki-yo's most layered and beautiful quality; highly effective for calligraphic and expressive writing
• Fine nibs — the deep blue-black reads with full clarity, legibility, and professional weight at fine sizes; an excellent everyday pairing; shading and sheen less prominent but colour performs cleanly and with authority
• Extra-fine nibs — fully functional; the deep blue-black base remains precise and high-contrast; shading largely absent; sheen not visible at this coverage level; a reliable choice for fine annotation and compact writing
• Eyedropper pens — high ink volume ensures full colour saturation and consistent shading and sheen expression; the generous wet flow of Tsuki-yo benefits from eyedropper capacity; particularly effective for showcasing the ink's full visual range
• Dip pens — excellent for fully showcasing Tsuki-yo's saturation, shading, and red sheen; broad dip nibs allow large coverage areas that reveal the full sheen effect; effective for expressive writing, night-sky illustration, and ink swatch art

Pen Maintenance

Pilot Iroshizuku Tsuki-yo (月夜) is a pH-neutral, dye-based ink safe for all pen materials including resin, celluloid, and ebonite. As a no-shimmer formulation, it carries no particle clogging risk and is low-maintenance across all pen types. Flush every 4–6 weeks under normal use.

Recommended Uses

• Everyday writing and professional correspondence — the deep blue-black is high-contrast, fully legible, and authoritative; professional enough for office and formal use, distinctive enough to be immediately recognisable as something more considered than a standard ink; one of the finest daily blue-blacks available
• Note-taking and study — the wet flow, fast dry time, and high legibility make Tsuki-yo an excellent note-taking ink; the deep blue-black reads clearly under all lighting conditions; a reliable companion for extended writing sessions
• Calligraphy and expressive lettering — the red sheen and medium shading are a compelling combination for decorative calligraphy; stub and italic nibs bring out the full tonal and sheen range; the deep teal-blue reads with authority in large-format lettering
• Journaling and creative writing — the moonlit night inspiration and layered visual character make Tsuki-yo a natural choice for personal journals and creative writing; a colour with emotional depth and quiet elegance
• Art and illustration — compatible with dip pen and brush application; the deep teal-blue base, expressive shading, and red sheen add depth and nocturnal atmosphere to illustration, night-sky artwork, and mixed media
• Ink collection and Iroshizuku series building — Tsuki-yo is a cornerstone Iroshizuku colour and the series' defining blue-black; pairs naturally with other Iroshizuku inks in the blue and blue-green families (Ama-iro, Shin-kai, Kon-peki) for a complete Japanese blue palette
• Fountain pen photography and swatching — the deep teal-blue photographs richly under natural light; the red sheen is most apparent in raking light at stroke edges and swab centers; a highly photogenic ink with a layered, atmospheric quality

About the Iroshizuku Collection

The Iroshizuku (色彩雫 — literally drops of colour) collection is Pilot's premium fountain pen ink series — a range of sixty inks, each named for a plant, flower, or natural phenomenon drawn from the Japanese landscape, and each formulated by Pilot's in-house ink chemists to translate that natural reference into a precise, vivid, and beautifully behaved fountain pen ink. The series was first launched in 2008 and has remained, in the years since, the benchmark against which Japanese premium inks are measured: consistent, safe for all pens, beautifully bottled in the flat-sided 50ml glass flask with its built-in ink well, and formulated to a quality standard that has established Pilot as one of the world's great fountain pen ink makers.

About Pilot

Pilot Corporation is one of Japan's oldest and most respected writing instrument manufacturers, founded in 1918 and producing fountain pens, inks, and writing instruments for over a century. Pilot's commitment to precision manufacturing and ink formulation is reflected throughout the Iroshizuku line — inks that are among the most consistently well-reviewed, most widely used, and most beloved in the global fountain pen community.

Product Specifications

Available at Shosai — Ottawa–Gatineau

Shosai (shosai.ca) is a fine stationery boutique serving the Ottawa–Gatineau National Capital Region. We carry a curated selection of premium fountain pen inks, papers, and writing instruments from the world's most respected stationery brands.

• 📍 In-store pickup: Gatineau, QC — J9J 0K6
• 🛵 Local delivery: Available in the Ottawa–Gatineau area
• 🚚 Canada-wide shipping available
• 🇫🇷 Service bilingue — français et anglais

Whether you are new to fountain pens or a seasoned collector, Shosai is your local destination for inks that go beyond the ordinary.