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191

Science and Justice 48 (2008) 187–

Erasable ink; something old, something new

John Welch

Forensic Science Service Ltd., London Laboratory, 109 Lambeth Road, London, SE1 7LP, United Kingdom

Received 4 May 2007; received in revised form 15 November 2007; accepted 16 November 2007

Abstract

Writing made with the Frixion ® rollerball pen by Pilot ® can be made colourless using the eraser incorporated in each pen. The heat generatedby the friction between eraser and paper decolourises the ink and other sources of heat have a similar effect. The original colour of the ink isrestored by cooling it to a temperature below 20 °C.© 2007 Forensic Science Society. Published by Elsevier Ireland Ltd. All rights reserved.

Keywords: Erasable; Ink; Ball-pen; Heat sensitive

1. Introduction

The long established Papermate “Replay” erasable ball-pen,introduced in the USA in 1979, has been re-branded, in theUK, as“Eraser.max”. A recent addition to this class of writinginstruments is the Pilot “Frixion” erasable rollerball pen, whichthe author first saw advertised in April 2006. The mechanism bywhich the ink-line of this new pen may be erased is radicallydifferent from that which applies to the earlier product. Someobservations on, and testing of, writing made with both sorts ofpen are reported below.

Forensic scientists specialising in the examination of ques-tioned documents have long been familiar with the erasable ball-pen sold in the UK under the product name of “Replay” andmanufactured by Papermate. The ink-line produced by that penhas a distinctive appearance under low-power microscopy. Itappears as a smear of viscous jelly calling to mind the colouredrubber cement, which approximates the composition of the ink,accompanied, at intervals, by short, hair-like tendrils or filamentsextending outwards from the edges of the ink-line ( Figs. 1 and 2).The decline of the ease of erasure with increasing time fromwriting is a reported characteristic andmethods of determining thewording erased have also been reported [1–8].

Comparatively recently, in the experience of the author andhis immediate colleagues, the Papermate company has marketedin the UK another erasable ball-pen under the name “Eraser.max”. The appearance of the ink-line from that pen is similar to

E-mail address: john.welch@fss.pnn.police.uk.

1355-0306/$ - see front matter © 2007 Forensic Science Society. Published by Elsdoi:10.1016/j.scijus.2007.11.002

that of the ink-line from “Replay” but less markedly so. TheEraser.max pen has a small eraser fitted into the pen top. In use itremoves the bulk of the written line but a pale trace of it remainsreadily visible to the unaided eye. For black Eraser.max that paletrace is luminescent under conditions for red and infraredluminescence even though the original ink-line was not. BlackEraser.max is opaque to visible and infrared radiation in therange 570 nm to 1000 nm.

During April 2006 the Pilot company began advertising inUK newspapers the “Frixion” erasable rollerball pen. It isadvertised as being available with black, blue, red, green, lightblue and purple coloured inks but the first four are the mostreadily available and were the four observed for this study.

2. Experimental

Observations on ink-lines from Frixion rollerball pens weremade with the standard techniques of the forensic documentexaminer: the unaided eye; stereo-zoom low-power microscopy(×7 to ×42 linear); a variety of dichroic filters; long-wave andshort-wave ultraviolet light; electrostatic detection (Esda),infrared viewing and infrared luminescence. The last twotechniques were conveniently provided by the VSC2000HRinstrument manufactured by Messrs Foster and Freeman Ltd.and the electrostatic detection made use of the apparatus namedfor that technique from the same manufacturer. The paper usedthroughout was a standard, plain white, office and photocopypaper; “Niceday 3500”, 80 gsm. The ink-lines were manipu-lated using the erasers that were within the bodies of the Frixion

evier Ireland Ltd. All rights reserved.

Fig. 1. “Replay” ink-lines at ×40 linear magnification.

188 J. Welch / Science and Justice 48 (2008) 187–191

pens; with heat from a domestic laundry iron and from a do-mestic hair-dryer; and by cooling in a domestic freezer.

3. Observations

The Frixion pens contain a mobile, liquid ink and write verysmoothly producing ink-lines visually similar to ordinary liquid-

Fig. 2. “Replay” ink-lines at ×

ink rollerball pens. Microscopically, the ink-lines exhibit thefollowing characteristics:

(i) a slightly indented groove central to the coloured line.(ii) an extra deposit of ink where the pen lifts from the paper.(iii) a “powdery” appearance as if the dried ink was finely

granular.

40 linear magnification.

Fig. 3. Erased “Frixion” writing by normal light and infrared luminescence.

189J. Welch / Science and Justice 48 (2008) 187–191

(iv) paradoxically, in view of (iii), a soaked-in appearance(and despite that, the extra deposit at line-endings can bethick enough to cast a shadow with very low-angleillumination).

The absorbance by Frixion ink of radiation in the red andinfrared region of the spectrum varies according to the colour ofthe ink. That of the green ink extends furthest into the infrared buteven so that ink is transparent at 715 nm and longer wavelengths.All four colours were luminescent under conditions for red andinfrared luminescence [9,10].

Samples of writing in Frixion inks were viewed throughseveral dichroic filters [11]. Each dichroic filter was a combina-tion of a blue and an orange filter chosen from the range of eachsupplied by Lee Filters [12]. The effect of dichroic filters in thiscontext is thought to depend on the colour vision of the observer.In particular how the observer's colour vision interprets anabsence of light from part of the visual field where, for example,an ink-line is reflecting no light that the filter will transmit, whenthe remainder of that visual field is saturated with the colour,reflected from paper, that the filter will transmit. Viewed througheach of the dichroic filters used by the author the blue Frixion inkappeared black and the black Frixion ink appeared red. The othertwo colours of ink appeared to be only slightly modified by thefilters.

Under 366 nm and 254 nm ultraviolet light all four colours ofFrixion ink simply appeared dark against the bright paperbackground.

The body of each of the Frixion pens is fittedwith an eraser thatis made of a hard but conformable polymer with a slightlytextured surface. It appears from the manufacturer's advertisingthat the action of the eraser is not so much to abrade the ink-line

but to generate heat through friction and decolourise the ink-line.Writing made with each of the Frixion pens was rapidly andcompletely decolourised by the heat from a domestic iron, at amoderately hot, “two dot”, setting applied through a protectingsheet of plain white A4 paper. The heat from a much cooler iron,“one dot”, applied in the same way achieved the same effect.Indeed, the heat radiating from the iron onto the writingdecolourised the inkswhen the ironwas still one or two centimetresfrom them. The air-stream from a low-power domestic hair-dryeron its low setting decolourised an A4 page of “Frixion” writing in1–2min. The temperature of the air-stream at the paper surfacewasapproximately 50 °C. The time taken to decolourise an A4 page ofwriting may seem excessive but, at that temperature, applyingwarm air for a short time produced only transient decolourising.The colour of the inkwould return in one area of the page as the air-stream was moved to another.

The colourless writing lines resulting from the application ofheat could be observed by their sheen differing from that of thepaper surface when the page was observed at a shallow angleopposite a desk-lamp or other extended light source. (A techniqueor observation known as “specular reflection” in theUK “refractiveindex” in the USA.) Under ultraviolet light the colourless linescould be seen clearly as dark lines against the fluorescentbackground of standard office paper. Under conditions for redand infrared luminescence the colourless ink-lines luminesced in afashion similar to that of the original ink-lines. Examination withelectrostatic detection apparatus of a page bearing original ink-lines and ink-lines decolourised by the application of heat revealedboth as white lines against the grey background.

Placing the sheet with the decolourised writing on it in adomestic freezer at about −23 °C restored the writing to fullvisibility within 1 h.

Fig. 4. Erased “Frixion” writing by normal light and infrared luminescence.

190 J. Welch / Science and Justice 48 (2008) 187–191

Writing made with the Frixion pens and then erased using thepen-end erasers was detectable as an indentation by oblique lightand as a smear of luminescent material under conditions for redand infrared luminescence. Erasing more thoroughly so as toremove the decolourised ink fragments more fully from the papersurface or, at least, to disperse them more widely, had theparadoxical effect of making it easier to read what had been

Fig. 5. The erasure shown in Figs. 3

erased. The luminescence from the small portion of the inkremaining in the ink-line was easier to observe and decipher in theabsence of the much larger quantities of ink removed from theink-line andwidely dispersed ( Figs. 3 and 4). If the bulk of the inkremoved from the ink-line remains close-by the appearance underconditions for luminescence is of a luminescent smear, easilydetected but hindering the interpretation of what was written.

and 4 after cooling to −23 °C.

191J. Welch / Science and Justice 48 (2008) 187–191

Frixion ink decolourised and largely dispersed by the pen-enderaser was also detectable as a faint, dark trace under ultravioletlight.

That portion of the ink left in the ink-line by themore thorougherasing and dispersing of the bulk of the ink was restored tovisibility, faintly, by approximately 1 h at −23 °C (Fig. 5).

4. Conclusion

The rebranding of Replay pens as Eraser.max and, moreimportantly, the introduction into the UK of the Frixion erasablerollerball pen increase the likelihood of erased or decolourisedwriting in ink featuring in criminal activity. This short paperalerts the forensic science community to the existence of theerasable rollerball pen and describes some of the properties ofits ink. The indentation of the ink-line; the strong luminescencedisplayed by traces of the ink; the appearance of thedecolourised ink-line by specular reflection; its dark appearanceunder ultraviolet light; the restoration of colour by cooling; allprovide avenues by which the forensic document examiner maydetect the erasure and determine what has been erased.

Acknowledgement

The author acknowledges with gratitude the support andencouragement of his colleagues in the Questioned DocumentsSection of Forensic Science Services Ltd.

References

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