OPUS 88 Harmony Fountain Pen - Mocha Mousse

A soft café toned demonstrator with warmth 

The Opus 88 Harmony Mocha Mousse is a full sized eyedropper fountain pen finished in a muted coffee-inspired resin with soft purple translucency and layered depth. It blends warm neutral tones with Opus 88’s high capacity writing system, creating a pen that feels calm and effortlessly usable.

What sets it apart

• High capacity eyedropper filling system for extended writing
• Shut-off valve prevents leaks
• Soft mocha mousse resin with warm, neutral translucency
  
• Comfortable full size design suited to long writing sessions
• Size #6 Jowo nib unit for easy nib swaps

Feel in the hand

The Mocha Mousse feels warm and elegant. Its neutral coffee tone creates a relaxed writing environment that doesn’t compete for attention, making it easy to settle into your writing.

Who it’s for

• Writers who prefer neutral colour palettes
• Ink users who value high capacity pens for long sessions
• People who like understated demonstrators with muted tones
• Journaling, planning, and daily writing users
• Nib explorers who enjoy swapping out nibs

Not for

• Users who prefer bright or highly saturated colours
• Those who want compact or pocket-sized pens
• Writers looking for bold, high contrast design statements
• Anyone who prefers opaque metal or heavily decorative finishes

Practical tips

• Keep the shut-off valve slightly open during writing
• Close the valve before transport to prevent leakage
  
• Try different #6 nib styles to fine-tune writing feel

FAQs

Is the Mocha Mousse fully transparent?
It is translucent, allowing ink visibility while diffusing it through a warm coffee tone

Does it use cartridges or converters?
No, it uses an eyedropper filling system with a shut-off valve

Do I need to add silicone grease on the grip threads to prevent leaks?
No, the design includes a thick o-ring already.

Is it suitable for beginners?
Yes, though it benefits from basic understanding of eyedropper pens

Can it handle document and shimmer inks?
Yes, with regular cleaning recommended

What nib does it use?
Standard #6 JoWo-compatible steel nib

What other nibs is it compatible with?
Other size #12 JoWo nib units and also the nib unit from the Pilot Parallel art pen

What’s included

• Opus 88 Harmony Mocha Mousse Fountain Pen
• Eyedropper 
• Spare small o-ring for back of grip section
• Instruction leaflet
• Free nib tuning by LarryPOST

Ink pairing suggestions

• Sepia inks for cohesive café tones
  
• Teal inks for balanced complementary contrast
• Deep blue inks for clean everyday writing

Build your practice

• Pilot Iroshizuku inks for intensity and volume
• Herbin inks for colour range
• Midori notebooks with cream paper for calm feel

Specifications

• Brand: Opus 88
• Brand series: Harmony 
• Launch: 2024
• Origin: Taiwan
• Nib: Jowo #6, rose plated stainless steel
• Nib sizes: EF, F, M, B, 1.5mm stub
• Filling system: Eye dropper
• Material: Translucent acrylic
• Trim: Rose-gold coloured
• Weight: approx. 25g (capped)
• Length: approx. 146mm
• Diametre: approx. 15mm
• Comparable size: Twsbi Diamond 580

Pretty and dependable, inspiring you to start and continue.