# OPUS 88 Demonstrator Fountain Pen - Mocha Mousse

### A warm, coffee-toned pen with effortless writing comfort

The Opus 88 Demo Mocha Mousse is a full-sized fountain pen finished in a rich, coffee-inspired brown opaque acrylic. It provides a softer, more grounded aesthetic than the original clear demonstrators. Built around a high capacity eyedropper filling system with a shut-off valve, it is designed for long, uninterrupted writing.

### What sets it apart

-   High capacity eyedropper filling system for extended writing sessions
-   Shut-off valve provides control and reduces risk of leakage during travel
-   Warm mocha toned acrylic with a soft, coffee-inspired theme
-   Large, ergonomic form designed for comfort during long writing

### Feel in the hand

The Mocha Mousse feels calm, steady, and grounded. The warm brown tones create a sense of comfort and familiarity, similar to a well-made coffee on a quiet desk. It encourages slow, thoughtful writing while still offering the visual engagement of translucency in the grip section.

### Who it’s for

-   Writers who prefer warm, earthy colour palettes over brights
-   Users who want high capacity pens for journaling or long writing sessions
-   Fans of the original demonstrator model who still want an opaque version
-   Those who enjoy coffee-toned, neutral desk setups
-   Anyone who values comfort and ink capacity in a daily writer

### Not for

-   Users who prefer compact or pocket-sized pens
-   Those who want cartridge or converter simplicity
-   Writers seeking highly bold, high contrast finishes  
    

### Practical tips

-   Open the shut-off valve slightly during writing to ensure consistent ink flow
-   Close the valve when transporting to prevent leakage
-   Fill slowly to avoid air pockets in the barrel  
    

### FAQs

**Is the Demo Mocha Mousse transparent?**  
Just the grip section for a glimpse of the ink flow and the end cap. 

**How does the shut-off valve work?**  
It controls ink flow from the barrel to the nib. Open it slightly while writing and close it when not in use or during transport.

**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 like all eyedropper pens, it requires a little more care than cartridge systems.

**Can it be used with document and shimmer inks?**  
Yes, but regular cleaning is recommended to maintain consistent flow.

**How large is the pen?**  
It is an oversized fountain pen designed for comfort and long writing sessions.

**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 Demo Mocha Mousse Fountain Pen
-   Eyedropper
-   Spare small o-ring for back of nib unit
-   Instruction leaflet
-   [Free nib tuning](https://www.larrypost.com.au/blogs/blogs/smooth-writing-with-fountain-pens?_pos=2&_sid=a2392eaaf&_ss=r) from LarryPOST

### Ink pairing suggestions

-   Sepia inks for a cohesive coffee toned palette
-   Chocolate browns for a deep, rich monochrome look
-   Burnt sienna inks for warm, earthy continuity  
    
-   Deep navy for a classic, professional contrast

**Build your practice**

-   [Pilot Iroshizuku](https://www.larrypost.com.au/collections/larrypost-brands-pilot-pen?filter.p.m.magento.brand_series=PILOT+Iroshizuku) 50mL ink for volume
-   [Herbin](https://www.larrypost.com.au/collections/larrypost-brands-herbin) inks, lots of browns
-   [Opus 88 replacement #12 nib unit](https://www.larrypost.com.au/products/opus-88-replacement-12-nib-unit-for-demo-omar-extra-fine?_pos=2&_sid=b4764611c&_ss=r)

### Specifications

-   **Brand:** Opus 88
-   **Brand series:** Demo
-   **Launch:** 2018
-   **Origin:** Taiwan
-   **Nib:** Jowo #6, black stainless steel
-   **Nib sizes:** EF, F, M, B, 1.5mm stub
-   **Filling system:** Eye dropper
-   **Material:** Acrylic, black clip
-   **Trim:** Stainless steel
-   **Weight:** approx. 27g (capped)
-   **Length:** approx. 147mm (capped)
-   **Diametre:** approx. 17mm
-   **Comparable size:** Twsbi Diamond 580

A high capacity fountain pen with a warm, coffee toned aesthetic.

## Details

- **Price:** 199.95 AUD
- **Vendor:** OPUS 88
- **Type:** Fountain Pen
- **Tags:** Category_LarryPOST, Category_LarryPOST/Brands/OPUS 88, Category_LarryPOST/Brands/OPUS 88/OPUS 88 Demo, Category_LarryPOST/New, Category_LarryPOST/New Products, Category_LarryPOST/Pens, Category_LarryPOST/Pens/Fountain Pen

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| Extra Fine | 199.95 AUD | In stock |
| Fine | 199.95 AUD | In stock |
| Medium | 199.95 AUD | In stock |
| Broad | 199.95 AUD | In stock |
| 1.5mm Stub | 199.95 AUD | In stock |
| Extra Fine Flex | 199.95 AUD | In stock |
| Fine Flex | 199.95 AUD | In stock |

## Images

- OPUS 88 Demonstrator Fountain Pen - Mocha Mousse
- OPUS 88 Demonstrator Fountain Pen - Mocha Mousse
- OPUS 88 Demonstrator Fountain Pen - Mocha Mousse
- OPUS 88 Demonstrator Fountain Pen - Mocha Mousse
- OPUS 88 Demonstrator Fountain Pen - Mocha Mousse
- OPUS 88 Demonstrator Fountain Pen - Mocha Mousse
- OPUS 88 Demonstrator Fountain Pen - Mocha Mousse

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> Source: [LarryPOST](https://www.larrypost.com.au/products/opus-88-demonstrator-fountain-pen-mocha-mousse-extra-fine-pvd-nib)
> Updated: 2026-08-29