Sleek, shiny, black and white. My countries national sporting colours, how could I not like that? Putting my obvious bias aside, I do think it is a fairly good looking item.The Tri Eraser has a triangular-ish body, and a triangular eraser core. The core sides are about 8mm in length, and the total length of the eraser core is about 122mm, of which about the last 15mm is effectively unusable as its held in the mechanism.
The triangular body is quite comfortable to hold, and it certainly isn’t prone to rolling around on your desk. There is an integrally moulded pocket clip on the top section. The core is advanced mechanical pencil push top ratchet style by pushing down the white end section. The mechanism feeds fairly well, but not as precisely as a mechanical pencil. Replacement eraser cores are just fed in through the triangular hole in the top of the end section.
By holding the eraser at about a 45 - 60 degree angle and rotating which side of the triangle you use you can keep some sharpish edges and small sections available to do some detailed erasing.
The core is held fairly tightly by the mechanism but if you push down strongly the core will slide back up into the body. This is a bit of a problem if you press down hard whilst erasing as the core can slide back up into the body. Obviously this is most pronounced when holding the eraser vertically, but even when held at about a 45 degree angle to the paper it can slide back up under heavy hand pressure and vigorous erasing. I don’t want to make more of this matter than is necessary. If you are doing a small to medium amount of erasing, erasing a precise area, etc then you should not have any problems. It is really only if you are erasing a large area with heavy hand pressure that you may run into problems with the core pushing back up into the body.
The Pentel website makes no mention of what the eraser core is or isn’t made from, but I found some shopping websites that claim it is latex-free and others that claim PVC-free. It’s clearly not latex but other than that, who knows? I have recently been doing a little Googling on non-latex eraser compounds and from plastics raw materials manufacturer’s sites, research sites, patent websites, etc its clear there are a lot of different non-PVC materials used. EP/PP (ethylene/polypropylene copolymer), styrene-ethylene/butylene-styrene block copolymers, SBS/PS (poly(styrene-butadiene-styrene) blended with polystyrene), and SBR (styrene butadiene rubber) are just some the fancy names you will find mentioned as eraser compounds. It’s also now clear to me that a few of the erasers I have looked at and thought were vinyl probably weren’t.
During my review time I felt that the erasing power of the Tri Eraser was reasonable but not exemplary. Certainly I felt that it did not erase as well as my benchmark, the Staedtler Mars Plastic. Being a relatively small core eraser the waste of the Tri Eraser did not tend to twist up into long strands, so I always had a bit of eraser dust to clear up afterwards. On then to the official test, Tri Eraser versus Mars Plastic, with 0.5mm HB grade mechanical pencil lead and 4B grade Staedtler Mars Lumograph woodcase pencil lead.From my preceding comment, I expected Mars to perform better than Tri Eraser on the official test. I was wrong, so I’m not sure where that leaves my original gut-feeling that it wasn’t as good as Mars Plastic. Basically the official test was a draw, both doing an equal job of erasing the HB and 4B lead. There was one difference though, which you can see in the photos. Note how Mars tended to smear the lead more than Tri Eraser. Some might claim this means Tri Eraser actually won the official test! I’m tempted to think this smearing is partly to do with the size of the eraser. The compound of the smaller Tri Eraser rubbing off the main body quicker, thus leading to less smearing?
So, I’d suggest you consider the Tri Eraser next time you need something erased.
- Best Points – Triangular core shape keeps a fine edge.
- Not So Good Points – The core sometimes sliding back up into the body.
- Price Range – Economy.
Dimensions – Length 125mm, triangle side length 13mm.
Staedtlers history is with woodcase pencils, and I get the impression woodcase pencils are still very important to them, maybe more important than mechanical pencils, and thus I have always assumed that if there was any choice required they would optimise their erasers for woodcase ceramic leads rather than polymer leads. On the other hand I don’t think there’s any argument that Pentels mechanical pencils are more important to them than their woodcase pencils. Not to imply their woodcase pencils aren’t important, but their mechanical pencils are a worldwide force whereas their woodcase pencils are basically Japan-only. Thus I am tempted to think that Pentels erasers would be optimised for mechanical pencil polymer leads, should there be any conflict between eraser requirements.
Like many erasers the Pentel Hi-Polymer has a sliding cardboard sleeve. The eraser compound is white, and soft, noticeably a different white to Mars Plastic and definitely softer. Perhaps this softness might be an important consideration on thinner or more fragile papers, but in general use I found the softness a little annoying as it made the whole eraser flex and bend more when under pressure, and thus it felt a little less under control. As claimed, the eraser waste sticks together. I tried to compare the amount of waste produced and how well it stuck together with Mars Plastic but gave up. Too hard to be objective, but I am tempted to think the Pentel eraser wore down a little quicker than Mars Plastic.
Mechanical Pencil polymer lead, 2B hardness. 
Woodcase Pencil HB and Mechanical Pencil HB.
Woodcase Pencil 4B hardness. 
What did all that testing tell me? It told me that it’s pretty hard to tell these two erasers apart when it comes to erasing performance. Both do a great job on both woodcase and mechanical pencil leads. As expected, although still good, their worst performance was on the woodcase 4B lead. Smearing is always a little bit of a problem with such dark soft leads. This 4B test was the only one where I thought there was a little bit of a difference between the two erasers - it’s very close, but I did feel that Mars plastic did a slightly better job than Pentel Hi-Polymer on the 4B test. But very close, as I say.
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