KUM Blue Ocean pencil set

KUM Blue Ocean pencil set

KUM is a well known pencil sharpener manufacturer. Though inhabiting a very specialized market, they have an enviable reputation as a quality manufacturer with international distribution.

What may not be as well known is that KUM sells pencils – three by my count, all part of larger product offerings.

KUM Blue Ocean pencil set

Today we’ll look at the KUM Blue Ocean. At first glance it appears to be a small barbell – perhaps a discreet exercise product for office workers.

Closer inspection reveals that this is a pencil – housed at one end by an eraser, and at the other by a plastic cap. We’ll look at each of the three devices in turn.

The eraser is gigantic for a pencil cap type eraser – a black mini-football marked with the KUM logo on two sides. It does erase quite well. It weighs in at 10.7g.

The cap is marked “KUM since 1919”. It is black grooved plastic, with the appearance somewhat clunky in my view. The top of the cap has a true “cap” – a small piece of attached plastic that can be removed to reveal a red plastic sharpener.

Typical of a KUM product, there is a screw on the blade, and I suspect that the blade is replaceable. It works as a sharpener, but it is challenging to get a proper grip.

The cap/sharpener weigh 6.7g.

The pencil itself is marked in silver on matte black, “KUM Blue Ocean KUM”. It is 125mm long, below standard length.

The cap is rounded but unfinished. The wood is very pale – basswood?

The lead is a surprise – a very dark 2B perhaps, good though not the smoothest.

So back to the barbell comparison – a typical modern pencil is 4g, and the Blue Ocean pencil is 3g. But this eraser is 10.7g and the cap 6.7g. So this is a lopsided barbell.

All aspects of the product have problems. The eraser is simply too heavy to be a pencil cap eraser. At triple to quadruple the weight of a woodcase pencil, a pencil falls backward out of one’s hand with this eraser attached.

Even with a tightened grip, the balance is all off. While perhaps KUM wanted to offer value, or the appearance of a substantial eraser, a 10.7g eraser is simply too heavy for a pencil cap eraser.

The cap/sharpener is awkward and clunky. It does not taper towards the pencil, and cannot be comfortably held.

KUM Blue Ocean pencil set

KUM’s concept is not new to us. I think we have to give credit where it is due, and thank Faber-Castell for their Perfect Pencil line. However, unlike the Faber-Castell products, KUM’s Blue Ocean product is not practical, and barely usable.

I commend KUM for trying something new – but the execution leaves much to be desired.

Some more erasers

Our last look at erasers got some good feedback, so I thought I’d try four more erasers, though in a much more limited way.


We’ve established that erasers have to be judged in context, and this time we’ll narrow that context – one type of graphite on one type of paper. In particular, our reference pencil, the Staedtler Mars Lumograph 100 in HB, on an 80g/m2 Rhodia pad. Though not the cheapest brands, Staedtler and Rhodia have near-global distribution, so they seemed appropriate choices as references.

The four erasers are the Faber-Castell 7081 N Vinyl Eraser, made in Germany, the Pilot Foam Eraser, made in Japan, the Tombow Mono Plastic eraser, made in Vietnam, and the Sanford Magic Rub 1954, origin unstated.


All erasers were purchased new. The Magic Rub came loose, and the others were wrapped in cellophane. The three cellophane wrapped erasers also have paper sleeve holders.

Appearance wise, the Magic rub seems to have many air bubbles, and is a greyish off-white. The other three were variations of white.

On the Rhodia pad, I drew ovals from an Acme template, and shaded in a diamond pattern.


I’ll admit my expectation – I thought these erasers would all be roughly the same. All did well, but there wasn’t any doubt for me about which were best and worst.

At both lines and shaded areas, the Magic Rub was clearly the worst. Also fairly clearly, the Faber-Castell was the next to worst eraser in both tasks.

At lines, the Pilot Foam seemed best, with the Mono close behind. The positions were reversed with shaded areas.


I made some additional marks for an overtime round, and the Mono came out ahead. The differences are subtle, and hard to capture without professional equipment.


The description at Dick Blick suggests that the Magic Rub isn’t a paper eraser – which might explain the performance.

Further reading: Effects of eraser treatment on paper, American Institute for Conservation, 1982.

Stationery Magazine

Stationery Magazine

I can’t read much of it, yet it seems to speak very well to many interests of mine.

Red and blue pencils, leadholders, quirky office accessories – they’re all here, and featured prominently.

The magazine is in Japanese, with about 150 glossy pages crammed full of photos of woodcase pencils, mechanical pencils, leadholders, erasers, sharpeners, staplers, hole punches, rulers, and much more.

Stationery Magazine

Yes, they have a page on Vernier calipers:

Stationery Magazine

Sharpeners also.

Stationery Magazine

Stationery Magazine

Erasers: The Pink Pearl, the Staedtler Mars plastic, and others.

Erasers: The Pink Pearl, the Staedtler Mars plastic, and others.

Let’s take a look at some popular pencil erasers.

When I’m taking notes at a meeting, I rarely use an eraser. There just isn’t time. I strike out the error, and carry on. But at my desk or at home, the ability to correct one’s writing, charts, and drawings is a major benefit of the pencil. It’s especially great when the eraser works well.

I wanted to look at the two leading erasers that I see in the marketplace – the “Pink Pearl”, and the “white vinyl” type, specifically the Staedtler Mars plastic. I’ve also added in a gum eraser, and a kneadable eraser. There are still other types of erasers, but I think these four represent the main categories one would encounter in an office or art supply shop. I specifically wanted to test the Pink Pearl and Mars plastic side by side since they are so well known.

The science behind gum, rubber and erasing is interesting, but out of our scope today. There are some links below for further reading.

For the test, I sought brand new erasers at local stores. The Mars plastic came fully wrapped. The Pink Pearl was in a “blister pack” of three, the Lyra kneadable eraser was partially wrapped, and the General’s gum eraser was loose. The exact models used were:

General’s Gum Eraser No. 136E

Dixon Pink Pearl 101

Staedtler Mars plastic 526 50 UP

Lyra Knetgummi 3467

My reference pencil, the Staedler Mars Lumograph 100, was used for the first round of tests. A second test suite was done with Pentel Hi-Polymer Super 0.9mm HB lead, used in a mechanical pencil. This was partly to contrast the pencil lead types, as well as give the erasers additional tests.

Four paper types were chosen to represent a spectrum of types and quality. Two cheaper papers (Office copy, Moleskine), and two better quality papers, including watercolor paper – Rhodia, and Strathmore cold press watercolor. The exact papers were:

Xerox Business 4200 20lb. 75g/m2, 92 brightness


Rhodia vellum paper 21.3lb 80g/m2

Strathmore Watercolor cold press 140lb 300g/m2

Two type of markings were made – a straight line, and a doodle/shading of a square area.

I took photos as well as having the original documents for comparison. I realized that this also turned out to be a test of the papers and leads from the erasure perspective.

Here is a test sample, the Mars Lumograph 100 on Rhodia, before and after erasure.

Erasers: The Pink Pearl, the Staedtler Mars plastic, and others.Erasers: The Pink Pearl, the Staedtler Mars plastic, and others.

Here are the scores. The erasure results were ranked 1 to 4, with 1 being the best erasure, and 4 the worst erasure.

Chart 1: Lumograph 100 line erasure

Xerox Moleskine Rhodia Strathmore
Gum 2 1 2 2
Pink Pearl 4 4 4 4
Mars plastic 1 2 1 1
Kneaded 3 3 3 3

Chart 2: Lumograph 100 drawing erasure

Xerox Moleskine Rhodia Strathmore
Gum 2 1 3 1
Pink Pearl 4 4 4 4
Mars plastic 3 2 1 2
Kneaded 1 3 2 3

Chart 3: Pentel Hi-Polymer Super line erasure

Xerox Moleskine Rhodia Strathmore
Gum 2 3 2 2
Pink Pearl 4 4 4 4
Mars plastic 1 1 1 1
Kneaded 3 2 3 3

Chart 4: Pentel Hi-Polymer Super drawing erasure

Xerox Moleskine Rhodia Strathmore
Gum 1 3 3 1
Pink Pearl 4 4 4 4
Mars plastic 2 1 1 2
Kneaded 3 2 2 3

Interpreting these results, the Mars plastic is the best or almost the best at erasing lines on all types of paper. Erasing a Lumograph 100 drawing, the General’s Gum eraser performed slightly better. At Pentel drawings, the kneaded eraser did very well, though not better than the Mars.

The overall test winner is the Staedtler Mars plastic, with a nod to the General’s Gum for woodcase pencil artists, and kneaded erasers for mechanical pencil artists. As the results depended on the task and type of lead and paper, the real lesson is that an eraser has to be looked at as part of a pencil/paper/eraser combination, and in the context of usage.

The Pink Pearl was a disappointment. It came last in all sixteen invividual tests, and sometimes left a pinkish smear.

The kneaded eraser has a major benefit that became apparent as my desk got filled with eraser detritus: Kneaded erasers leave no residue, since they absorb the graphite as they erase. The eraser thus gradually becomes darker (and dirtier) over time.

An observation about the pencil lead is that the mechanical pencil lead is much more erasable – remarkably so in some cases. The Pentel markings on the Moleskine and Rhodia seemed to just disappear with the Mars eraser. The mark’s only remaining evidence seemed to be indentations in the paper from the pencil’s pressure – and these require careful examination to see.

The photocopy paper and the artist’s watercolour paper – neither of which were created for pencil use – retained the most graphite after erasure attempts.

Further reading:

Erasers World A collection and information site for erasers. Several interesting company biographies, as well as essays on erasers and eraser materials.

Joy of Erasers Blog devoted to erasers.

Wikipedia eraser article Not bad for Wikipedia.

Chemical & Engineering News Informative non-technical article on erasers.

Staedtler document on erasers (700K PDF) A mix of technical and marketing information about erasers.

Kokuyo Kadokeshi U700 eraser

Kokuyo Kadokeshi U700 eraser

A fascinating eraser from Japan.

This eraser is a 2 x 2 x 5 block of 10mm sided cubes, with half the cubes scooped out.

Kokuyo Kadokeshi U700 eraser

There is apparently a “big brother” U800 with 15mm cubes, and a version with a strap, for attachment to a cell phone. I’m not making that up.

It is intriguing and geometric. The many corners and edges and scoops create interesting shadows, and make it very eye catching. Yet, it remains just an eraser.

Kokuyo Kadokeshi U700 eraser

Introduced in 2003, the eraser is part of the Museum of Modern Art’s permanent collection, and was featured in a 2004 exhibition, “Humble Masterpieces”.

The eraser was designed by Hideo Kanbara as an entry in a competition held by Kokuyo.

Kokuyo Kadokeshi U700 eraser

It is also a commercial success, having sold over 6.5 million erasers in the first three years after the launch.

Kokuyo Kadokeshi U700 eraser

The Kokuyo website says the eraser has 28 edges. Of course, they mean corners. External corners in particular.

I was curious about what else Hideo Kanbara has designed. While there are a few concept drawings on the web, an intriguing “plug pin” was the only other commercially offered item that I found.


Official Kadokeshi website
Kadokeshi in the Museum of Modern Art
The plug pin by Hideo Kanbara