Our Research

Publications and research in relation to documents and writing instruments.


(Published in the International Journal SAFE (Scientific Association of Forensic Examiners 2017-2018)

Written by:
Tay Eue Kam & William Pang Chan Kok (Forensic Handwriting and Questioned Document Examiner)

Below is a summary of an experiment that we have conducted on the FriXion Erasable Ink pen.

Pencil is usually used when we know that we can correct any mistakes made by erasing any mistakes in our written notes. In recent years, new pen technology has introduced the erasable pen. When the first erasable ballpoint pens were introduced, the ink was pale and blotchy, and the eraser tore through the page. Further innovation has made the erasable pen of today better, more colourful and friendlier to the user.

Many of this special thermo-sensitive ink come in bold, bright colours and erases almost without a trace by rubbing the hard stub provided on one end the writing instrument. Unlike pencil, the rubbing process does not leave any messy residue for cleaning up. This leaves a questioned for document examiners in the examination. Is the erased writing detectable? If yes, how is this detection possible and what methods can be used?

There are three main type of erasable ink pens:

  1. Thermo-sensitive Erasable Ink Pen: The Pilot FriXion pen, The Uni-ball Fanthom gel ink pen. The ink disappears when exposed to heat.
  2. Erasable Ink Pens + Ink Erasing Marker: Stabilo Point 88, Colorkilla Erasable Fineliner Marker Pen. The other type of erasable pen is the one that comes in a set of the pen with the “eraser”.The ink is erased when a separate erasing ink is applied. However, the erased area can be detected.
  3. Traditional Erasable Ink Pens: Uni-ball Signo gel ink pens. This is the ink pens that can be erased with a rubber ink eraser.

Images taken from our experiment:​

pha handwriting our research pic 101

Frixion Erasable ink is detectable by the following:

  1. By visual inspection for indentation using oblique lighting.
  2. The erased ink will disappear but the indentation exists and there will be some remnants of unerased area that can be detected under higher magnification and oblique lighting. Depending on the pressure applied in the writing, where the pressure is light, the indentation may not be clearly visible.
  3. By depositing the document again in the freezer after erasing the ink, the ink will reappear.