Opus 88 Koloro Demonstrator Review

Opus 88 is a brand that’s really burst onto the fountain pen scene in the last year or so. Though I wasn’t quite taken with the design of the original Koloro models, a glut of positive reviews for the Koloro Demonstrator forced me to take another look at the brand. So is this pen good enough to have me singing its praises?

The Pen

Materials & Construction

Opus 88 makes use of a clear resin in the Koloro Demonstrator. Portions of the pen are completely transparent, such as the end caps, while other parts have a frosted, translucent appearance, such as the cap and barrel. It’s a tasteful combination that adds some interesting visual character to the material. It’s definitely a more modern aesthetic and certainly won’t work for some, but personally I’m quite smitten with it.

The clip is made of a metal and is coated in an attractive matte black finish. It has a nice amount of spring to it and can be flexed quite easily. The clip is broader towards the top and tapers toward a rounded ball at the base. Visually, the clip reminds me of some of Pilot’s clip designs, but I find Opus 88’s to be more functional. 

In terms of build quality, I see no causes for concern. The pen feels rock solid with no discernible gaps between the components. There are no rattles or loose parts; everything fits snugly. If I had to name one complaint in this area it’s that the eyedropper knob was a bit squeaky initially, but it seems to have worked itself out over time. Now, there’s a slightly ‘gritty’ sound when I turn it, but it’s not something I really notice or think about.

Also Read: TWSBI Eco Review

One of the downsides of the material is that it can be a bit tricky to clean. Though the majority of the barrel cleans out easily, ink can sometimes get into the threads and be tougher to clean out. Having access to pen flush and a syringe can facilitate the process, but it still does take some effort. 


Perhaps the most interesting element of this pen is its eyedropper filling system. For those who may not be familiar, an eyedropper system entails filling the barrel of the pen directly with ink, rather than using a separate component such as a cartridge, converter, or piston/vacuum mechanism. A glass pipet is included in the box and, while it works adequately, I prefer using a syringe to fill this pen as the finer tip of the syringe allows you to insert it deeper into the barrel and avoid any potential spillage. 

Notably, the Koloro Demonstrator is a ‘Japanese-style’ eyedropper. What that means is there are two chambers within the pen, with an internal valve that governs the flow of ink from one to the other. The larger chamber resides in the barrel of the pen and essentially functions as an ink reservoir. The smaller chamber rests in the pen’s section and allows the ink to flow into the pen’s feed and nib. 

Separating the two chambers is a small valve that can be manipulated via the knob on the back end of the pen. When the knob is unscrewed, ink can flow from the larger chamber into the smaller one. For extended writing sessions, it’s best to leave the valve open, but the smaller chamber does house enough ink that you won’t necessarily have to open the valve for shorter writing sessions. Having said that, I do still find it a small hassle to have to manage the two-chamber system. If you’ve ever used a vacuum-filler like the Pilot Custom 823 or TWSBI Vac700R, you’ll be familiar with the issue and may not be that bothered by it, but for those who aren’t familiar, you may find it to be a chore.

Another thing I don’t particularly enjoy about the Koloro Demonstrator is that the cap takes 4 turns to remove. This seems inordinately high in my opinion and results in a small, but noticeable, annoyance whenever you start or finish using the pen. Combine that with the fact that you’ll also be screwing and unscrewing the eyedropper knob from time to time and it’s easy to see that you’ll be spending a good amount of time twisting this pen. On the plus side, though, the nib is well-sealed and writes immediately even when left unused for longer periods of time. 

In the Hand

The Koloro Demonstrator is a big pen. At around 147mm long (capped), it’s easily one of the longest pens I own, almost as long as the Pilot Custom 823 (149mm, capped), which is currently the largest pen in my collection. As such, it makes sense that the cap can’t be posted, as doing so would result in something completely unwieldy. That fact rings even more true when you consider that, at 10g, the cap makes up almost 40% of the pen’s 27g weight.

The uniform cylindrical shape of the pen feels great in my hand, and I find I prefer it to more traditional tapered designs. Moreover, the step-down to the pen’s grip section is subtle and the section’s threads are formed in such a way as to be barely be noticeable. Speaking of the section, it’s got everything I look for: ample length and girth, and a gentle flare towards the nib that keeps my fingers from slipping. 

Maybe it’s just my overall fondness for the pen speaking here, but I actually feel like this pen makes my handwriting better. In looking over the various pieces of writing I drafted during my testing, my script consistently looks cleaner, crisper, and more uniform. Certainly, this could be a result of some combination of selective analysis and confirmation bias, but I do also believe that the pen’s ergonomics could be a factor. 

The Nib

Material & Design

Opus 88 makes use of a steel Jowo #6 size nib in the Koloro Demonstrator. Fine, medium, and broad sizes are available. The standard Jowo scrollwork and nib size designation are present on the nib, and Opus 88 adds their logo in the center. It’s a familiar and understated design. Part of me wishes that they had gone for a matte black finish on the nib, as it would pair nicely with the clip and barrel rod, but the silver nib works just fine, too. 


I’ll cut to the chase: the Opus 88 Koloro Demonstrator has one of the smoothest nibs I’ve ever experienced out of the box. Though it’s a standard Jowo #6 size nib, it’s ground to absolute perfection and glides effortlessly across paper. It’s so good, in fact, that I literally uttered an audible gasp the first time I wrote with it, and I’m not exactly an emotive person by nature. The eyedropper filling system keeps the ink flowing and affords a wet writing experience, especially when you keep the eyedropper valve open. I experienced no issues during my testing, and the pen wrote straight away even after going unused for two weeks. I really am at a loss for words for how much I like this nib, but suffice to say it’s quickly become one of my absolute favorite writers in the short time I’ve owned it. 


As of the time of this writing, the Koloro Demonstrator sells for $120 at most fountain pen retailers. Personally, I cannot think of another pen I’d rather have at this price point. Some may be put off by the fact that the pen does not include a gold nib, but I strongly encourage you to look past that. The Koloro Demonstrator may be a good option for you if: 

  • you appreciate pens with larger ink capacities; 
  • you enjoy smooth-writing nibs; 
  • you prefer unconventional, modern design aesthetic; 
  • you have larger hands or enjoy oversize pens; or
  • you enjoy demonstrator pens.

The only aspect of the pen that I can foresee as being problematic is its ergonomics. While I find it perfectly comfortable, I can definitely see how the pen may not work for some, given its larger dimensions. 

Perhaps the single greatest compliment I can give this pen is the following well-known adage: it’s so nice I bought it twice. I enjoyed my first Koloro Demonstrator so much that I bought a second one with a broad nib. I can’t stress how atypical it is for me to do that, especially for a pen that accepts a #6 size nib that can easily be swapped out. But I wanted the option of having both pens inked up at the same time, as well as the safety net of having a backup in case anything happens to one. There’s only one other pen in my collection of which I’ve purchased multiples (LAMY Lx), and even then the reason for doing so was an insane price reduction rather than pure fondness for the pen itself. 

Writing Sample

Final Thoughts & Score

What’s Hot

  • extremely smooth nib out of the box
  • uncommon filling system with ample ink capacity
  • chic design and comfortable ergonomics (unless you have small hands)

What’s Not

  • cap requires 4 twists to remove
  • eyedropper knob was squeaky at first
  • unsealing secondary chamber can be a small hassle




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