In 2007 the Japanese pen company, Pilot, launched its FriXion range of erasable ink pens. It had taken over thirty years to develop an ink that was completely erasable and that also flowed smoothly enough to be used in a ballpoint pen. The result was the Pilot Frixion erasable gel ink pen.
Pilot Frixion erasable gel ink pens use thermochromic ink, which is a temperature sensitive compound that changes colour when exposed to heat. Thus, the Frixion erasor, when rubbed over the ink, raises the temperature by friction to 60 degrees, at which point the ink “disappears”.
Creating The Ink For The Pilot Frixion Erasable Gel Ink Pen
Their solution was to use a third element, which locks the high-temperature forms of the ink, through a process of electron donation, making it more thermodynamically stable.
Another difficulty was getting the consistency of the ink right so that it would flow smoothly. The solution (no pun intended!) was to use a thermochromic material which could be rendered into fine microcapsules of no more than 50 microns. Each microcapsule contained the three elements, A, B and C. While A and B are attached the ink is visible. But, under friction, the temperature rises and C splits apart A and B and attaches itself to B, and the ink turns transparent and “disappears”.
Disappearing & Reappearing Ink
Exposing Frixion ink to other forms of heat apart from friction, such as a naked flame or hot air from a hairdryer will cause the ink to disappear. Exposure to direct sunlight for a prolonged period will also cause the ink to fade away.
If you wish, you can restore the ink to visibility by placing the paper on which it was written in the freezer for 10 minutes.
The first Pilot Frixion erasable gel ink pen to be sold on the market had a detachable cap. The eraser was placed at the top of the pen, which was not an entirely satisfactory arrangement as it meant that you could not put the cap on the top of the pen while using it, or rather, if you did, you had to remove it every time you wanted to use the eraser.
However, the more recent pens released for the Japanese market have a greatly improved design.
Pilot has dispensed with the annoying cap and designed a retractable pen. The retracting button is on the side of the pen in the form of a convenient pocket clip, so the eraser sits nicely on the top of the pen.
The lower third of the pen barrel is wrapped in a thin plastic cushion for more comfortable writing, and can be unscrewed to replace the refill.
The ballpoint cartridges are available in two different thicknesses – 0.5mm and 0.7mm. A nice design touch is the use of clear erasers to mark the 0.5mm pens and coloured erasors to mark the 0.7mm pens. There is also a little green sign at the top of the barrel telling you the thickness of the ink. Of course, when you need to replace the cartridge there is nothing to stop you using a different thickness or colour!
Pilot Frixion erasable gel ink pens that are released for the Japanese market can be purchased online from selected suppliers.