Table 1
Peer-reviewed articles and published (in conference proceedings) papers relating to the Solvent Loss Ratio Method (SLRM) (listed in chronological succession)
| Year | Author(s) | Reported scope of applicability | Information directly relating to the SLRM in the publication |
|---|---|---|---|
| 1996 | Aginsky | Several months | The SLRM was first published. It was described as a method for “Dating Inks by Evaluating Decrease of the Evaporation Rate [R%] of Ink’s Vehicle Solvents Due to Aging.” (Aginsky 1996) For a Senator (Germany) black ballpoint ink tested, the aging curve “R% – age of ink” leveled off within less than 6 months after the ink was placed on paper. When considering the scope of applicability of the SLRM it was stressed that the method is “effective to discriminate between fresh (age is up to several months) and old inks [about one year old or older].” (Aginsky 1996) |
| 2002 | Aginsky | 6 months | This conference paper reviewed the state of the art in the area of ink aging analysis in 2002 and, in particular, reported that, “The vehicle-to-dye ratio method [and the] ink dating method that evaluates decrease in the evaporation rate of ink volatile components as a function of the ink age [i.e., the SLRM] allow one to obtain a good correlation between the ink aging parameter measured and the actual age of ink for a period of time comprising up to six months after the ink has been placed on paper (document).” (Aginsky 2002) |
| 2002 | Gaudreau and Brazeau | 10 months | This conference paper reported the following two “broad time thresholds” for evaluating the actual age of ink on paper using the SLRM:
No aging curves and/or corresponding numerical data were reported in (Gaudreau and Brazeau 2002) (or in any other paper/article published thereafter) that would show that the ink aging parameter R% was correlating with the age of a particular ink(s) during a timeframe as long as 10 months (i.e., that the decrease of R% with the age of ink was statistically valid during up to 10 months after the ink’s placement on paper). |
| 2003 | Andrasko | 4 to 6 months | A modified SLRM (involving a different sample preparation—solidphase microextraction) was reported as being able to “reveal if an ink is fresh (4–6 months old at most)” (Andrasko 2003). Andrasko later communicated his strong doubts about the feasibility of such ink dating methods stating that the method he had presented was unreliable and that the results were not reproducible (Weyermann et al. 2011, p. 56). |
| 2006 | Wang et al. | 3 months | The study of 74 different blue ballpoint ink formulations (“of domestic and international origins”) (Wang 2005, 2006) was a continuation of the previous similar studies published in (Bezhanishvili et al. 1990) and (Aginsky 1993). Writing samples were produced every 2 weeks for 10 months. This ink aging method uses gas chromatography to measure the amount of phenoxyethanol (PE) and/or benzyl alcohol extracted from a sample of ink on paper (using acetonitrile with 2-cresol as an internal standard) and spectrophotometry to measure the amount of phthalocyanine or triarylmethane dyes extracted from the same ink sample. For each of the 74 inks tested, the PE/dye ratio was decreasing with the age of ink, and the aging curve leveled off within three (3) months after the ink was placed on paper. To make sure that results were repeatable, each test was repeated 5 times. Based of the results obtained, Wang et al. concluded that this ink aging method can only be used for determining the approximate age of ballpoint ink on document if the actual age of the writing is less than 3 months. |
| 2008 | Bügler et al. | Improved SLRM: 6 months | Bügler et al. have developed an improved (mass independent) version of the SLRM, in which a two-step thermo desorption of PE (first at a low temperature and then at a high temperature) is used instead of a liquid extraction of PE (Bügler et al. 2008). The improved SLRM uses elevated temperatures to “extract” PE from the same (that is why the improved SLRM is mass independent) ink sample—first a moderate temperature, such as 700C, and finally a high, “all-extracting,” temperature, such as 2000C, while the parent SLRM uses an extracting solvent to extract PE from two (different) ink samples, one of which is then heated at 700C to determine a PE loss during the heating process. As two ink samples, A and B, will typically contain different amounts of PE, the parent SLRM is a priori mass dependent (i.e., its ink aging results depend not only on the age of the ink but also on an inevitable and unknown to the examiner difference between PE contents in samples A and B), and thus it is less reliable than the improved, mass independent SLRM. Bügler et al. established that “fresh ink releases a relative amount of solvent at a certain low temperature in a defined period of time, which decreases as the ink ages. As a consequence, this relative amount of solvent [PE] released at a certain low temperature, and its decrease with time, can be used [as an age-dependent parameter] to estimate ink age. This agedependent parameter was studied in 85 different inks ranging in age from 1 week to 1.5 years. It was found that some [slow aging] inks showed a significant decrease of this parameter up to an age of several months, and that the aging process can be monitored within this period” (Bügler et al. 2008). “[A low] desorption temperature [T = 700C] seemed to be best suited to differentiate between fresh and old ink entries. Herein, ‘fresh’ means less than 3 month, and ‘old’ means more than 6 months.” Bügler et al. conclude the article as follows: “Practical casework confirmed that the dating procedure described herein can be applied to ink entries with a maximum age of several months” (Bügler et al. 2008). |
| 2010 | Gaudreau and Aginsky | 18 months | In 2010, the above 25%-threshold, which was reported in (Gaudreau and Brazeau 2002) and used to determine whether ballpoint ink on paper is less then 10 months old, was abandoned (as it showed multiple falsepositive results) and revised to an “R% value larger than 35% indicating the age of the ink to be less than 18 months” (Gaudreau and Aginsky 2010). However, no aging curves or numerical data were reported in the 2010 paper that would show that the ink aging parameter R% correlated with the age of a ballpoint ink(s) during a timeframe as long as 18 months (i.e., that the decrease of R% with the age of ink was statistically valid during up to 18 months after the ink’s placement on paper). Furthermore, a recent evaluation of unpublished experimental data (provided to this author by Marc Gaudreau in 2010) showed that, even if one were to use this new (revised) 35% threshold, multiple false-positive results were obtained for ink samples known to be older than both 18 months and 2 years. |
| 2011 | Weyermann, Bügler, Cantu, Almog | Outside proficiency testing using “blind” ink samples is necessary to test the validity of current ink aging methods | This article reviews the state of the art in the area of ink aging analysis and stresses as follows:
It should be noted that, as of present, no experimental data and/or results of outside proficiency testing have yet been published that would show that the ink aging parameter R% measured by the SLRM correlates with the age of a ballpoint ink on paper after the ink reaches the above age of “3–4 months.” |
| 2012 | Kirsch et al. | 3.5 months | The study was a further development of the previous works (Bezhanishvili et al. 1990, Aginsky 1993, and Wang et al. 2005, 2006). This ink aging method was based on using high performance liquid chromatography (HPLC) to measure the amount of PE (fluorescence at 310 nm) and triarylmethane dyes (absorbance at 580 nm). The decrease of the PE/dye ratio with the age of ink was evaluated using Neumann trend tests. For all inks tested, including “Medium Aging” Ink #2 (see Table 2 that follows), the aging curves leveled off within 3.5 months. (Kirsch et al. 2012) |
| 2012 | Bügler | 6 months | The application of the above improved (mass independent) version of the SLRM to 80 different ballpoint inks showed significant variations in slopes of aging curves between different inks. The aging curves obtained for slow aging inks leveled off after ca. 4 months. Bügler states that the “method is applicable if ink is not older than a few months” and that the only scientifically sound conclusion in an ink aging case (when using this improved version of the SLRM) is either “Ink fresher than 6 months” or “Case is Inconclusive.” (Bügler 2012) |
| 2012 | Koenig and Weyermann | < 2 months | The aging of the three inks, Cat. Numbers 1892 (ink #1), 1688 (ink #2) and 1774 (ink #3), which represent fast, medium and slow aging ballpoint inks, respectively (in Table 2 below, these inks are listed as inks 1, 2 and 3, respectively), was studied using the procedure for the SLRM described in (Gaudreau and Brazeau 2002). Writing samples with known dates of preparation were produced using strong, medium and weak writing pressure (350 grams, 250 grams, and 100 grams, respectively). In addition, different storage conditions were tested by keeping the writing samples 1) at normal laboratory environmental conditions, and 2) in a climatic chamber. It was found that the ink aging parameter R% depends not only on the age of ink but also on the writing pressure: R% significantly increased with increased writing pressure (i.e., with increased amount of ink deposited by the ballpoint pen on paper) (Koenig and Weyermann 2012). It means that if two entries, A and B, were written on the same day and with the ink of the same composition, they may nevertheless produce significantly different R% values, e.g., in any of the following two cases:
Besides, Koenig and Weyermann determined, for each of the above three inks tested, a timeframe during which the ink aging parameter R% was correlating with the age of the ink (that is, the timeframe during which the decreasing of R% with the age of ink was statistically valid). These timeframes were as follows: Ink #1 (fast aging ink): practically zero (R% does not correlate with the ink’s age at all) Ink #2 (medium aging ink): 19 days Ink #3 (slow aging ink): 48 days (Koenig and Weyermann 2012). |
Table 2
Ballpoint inks examined in this work.
| Ink # | Description (pertinent information on cartridge, barrel of the pen, etc.) |
|---|---|
| 1 | “Fast Aging” black ballpoint ink (Cat. No. 1892)* |
| 2 | “Medium Aging” black ballpoint ink (Cat. No. 1688)* |
| 3 | “Slow Aging” blue ballpoint ink (Cat. No. 1774)* |
| 4 | ZEBRA black ballpoint ink (Z-Grip pen, Med. Pt., made in China) |
| 5 | BIC black ballpoint ink (4-color pen, Med. Pt., made in France) |
| 6 | BIC black ballpoint ink (refill, Med. Pt., made in Mexico) |
| 7 | PILOT black ballpoint ink (refill, Med. Pt., made in Japan) |
| 8 | PENTEL black ballpoint ink (refill, Med. Pt., made in Japan) |
| 9 | AVERY black ballpoint ink (refill, Med. Pt., made in Korea) |
| 10 | UNI-BALL black rollerball ink (refill, bold – 1.0 mm, made in Japan) |
| 11 | BIC black ballpoint ink (Bic ATLANTIS, made in France) |
| 12 | BIC black ballpoint ink (Bic SOFT Feel, Med. Pt., made in U.S.A.) |
| 13 | BIC black ballpoint ink (Bic JOYAS) |
| 14 | PARKER black ballpoint ink (refill, Med. Pt., made in U.K.) |
| 15 | LAMY black ballpoint ink (refill, broad, made in Germany) |
[i] *Three inks marked with the asterisk in Table 2 (inks # 1, 2 and 3) were in ballpoint pen refills (cartridges) sent to this author by the European Document Experts Working Group (EDEWG) chairperson Jürgen H. Bügler, Ph.D. Dr. Bügler and his colleagues, Huns Buchner, Ph.D., and Anton Dallmayer, Ph.D., at the Institute of Forensic Sciences (Bavarian State Bureau of Investigation, Munich, Germany) had researched the aging of a representative set of ballpoint inks of different formulations, and as a result of that research, they have determined that the above three inks represent fast, medium and slow aging ballpoint inks, respectively. Since then, all of the three inks have been subjected to an extensive inter-laboratory EDEWG research project entitled “Ink Dating.” It should be noted also that these three inks were manufactured by large ink manufacturers in Europe and North America, and therefore each of these three inks can be found in numerous pens bearing different brand names. For example, at the level of TLC analysis, Ink #2 matches9 black ballpoint ink(s) used in pens of numerous pen companies, such as: Parker (UK); Pentel (USA); Papermate (France); Cartier, Dunhill, Dupont, Faber Castel, Hauser, Lamy, Montblanc, Waterman, Schmidt, Pelikan (all Germany); Montegrappa (Italy); Caran d’Ache (Switzerland); and Penatia (Cross, China).
Table 3
Scope of applicability of the SLRM for 15 ballpoint inks (BPI) examined in this work.
| Ink # | Description of Ink | How long a trend (a statistically valid decrease of R% as ink ages on paper) can be detected |
|---|---|---|
| 1 | “Fast Aging” black BPI | < 1 day |
| 2 | “Medium Aging” black BPI | ca. 3 weeks |
| 3 | “Slow Aging” blue BPI | < 2 months |
| 4 | ZEBRA black BPI (China) | ca. 1.5 months |
| 5 | BIC black BPI (France) | < 3 months |
| 6 | BIC black BPI (Mexico) | < 3 months |
| 7 | PILOT black BPI (Japan) | ca. 1 month |
| 8 | PENTEL black BPI (Japan) | < 1 month |
| 9 | AVERY black BPI (Korea) | < 1 month |
| 10 | UNI-BALL black rollerball ink (Japan) | < 1 month |
| 11 | BIC black BPI (France) | < 3 months |
| 12 | BIC black BPI (U.S.A.) | < 3 months |
| 13 | BIC black BPI (“JOYAS”) | < 3 months |
| 14 | PARKER black BPI (U.K.) | < 1 month |
| 15 | LAMY black BPI (Germany) | < 1 month |
Table 4
SLRM results obtained for six slow aging (#3, 5, 6, 11–13) and three other inks before and after indentation examinations using ESDA-2
| Ink: “age” | Before ESDA | After ESDA | ||||
|---|---|---|---|---|---|---|
| PE content, ng per 1-cm ink line | R% | PE content, ng per 1-cm ink line | R% | |||
| Unheated | Heated | Unheated | Heated | |||
| Ink #3: | ||||||
| 28 days | 47.5 | 32.9 | 31 | 38.2 | 27.1 | 29 |
| 2.5 months | 27.6 | 23.6 | 14 | 28.9 | 22.8 | 21 |
| Ink #4: | ||||||
| 1.5 months | 79.1 | 49.2 | 38 | 84.9 | 56.1 | 34 |
| Ink #5: | ||||||
| 7 days | 244.8 | 128.3 | 48 | 229.3 | 129.1 | 44 |
| 1.5 months | 231.2 | 137.1 | 41 | 214.6 | 120.8 | 44 |
| 2.5 months | 123.2 | 89.7 | 27 | 134.3 | 95.5 | 29 |
| 4 months | 174.5 | 136.5 | 22 | 151.7 | 115.3 | 24 |
| 6 years | 67.4 | 51.9 | 23 | 60.8 | 50.0 | 18 |
| Ink #6: | ||||||
| 7 days | 244.7 | 141.9 | 42 | 214.4 | 138.5 | 35 |
| 1.5 months | 193.9 | 127.0 | 34 | 186.5 | 116.0 | 38 |
| 2.5 months | 126.8 | 96.4 | 24 | 116.7 | 86.3 | 26 |
| 4 months | 149.4 | 116.5 | 22 | 161.9 | 134.0 | 17 |
| 6 years | 81.6 | 69.5 | 15 | 73.5 | 64.3 | 13 |
| Ink #7: | ||||||
| 28 days | 19.2 | 14.7 | 24 | 17.9 | 14.0 | 22 |
| Ink #8: | ||||||
| 28 days | 11.1 | 9.3 | 16 | N/A | N/A | N/A |
| Ink #11: | ||||||
| 4 years | 50.6 | 41.9 | 17 | 62.3 | 48.6 | 22 |
| 7 years* | 67.0 | 41.3 | 38 | 79.8 | 60.0 | 25 |
| Ink #12: | ||||||
| 4 years | 95.7 | 82.2 | 14 | 79.8 | 64.1 | 20 N/A |
| 7 years* | 83.8 | 59.5 | 29 | N/A | N/A | |
| Ink #13: | ||||||
| 4 years | 111.9 | 81.8 | 27 | 97.0 | 76.9 | 21 N/A |
| 7 years* | 90.5 | 59.0 | 35 | N/A | N/A | |
[i] *For the 7-year old handwritten entries (marked with the asterisk in Table 4), all pairs of ink samples were deliberately taken from curved portions of ink strokes and from the areas of ink lines which were close to the points of crossing of ink lines.
Table 5
SLRM and SET results obtained for known dated entries written with Ink #2 (“Medium Aging” ink) before and after the writing samples were examined using ESDA-2
| Age of Ink | Ink Aging Method | ||||
|---|---|---|---|---|---|
| SLRM | SET | ||||
| R% Before ESDA | Aging | D% Before ESDA | D% After ESDA | Aging | |
| 2.5 months | 11,* 22, 25* | No | 11.8, 12.5 | 11.6 | Yes |
| 4 months | 15,* 22,* 23 | No | 8.5, 9.7 | 9.5 | Yes |
| 7 months | 18,* 20, 23* | No | 6.7, 7.2 | 6.4 | Yes |
| 9 months | 6,* 12,* 14 | No | 4.7, 5.4 | 5.1 | Yes |
| 11 months | 12,* 20,* 21 | No | 0.9, 2.1 | N/A | No |
[i] NOTE: For each known dated entry listed in Table 5, first two SET tests were conducted before the entry was examined using ESDA (see column “D% Before ESDA”) and then one SET test was conducted (except for the 11-month old entry, the ink of which had ceased aging) after the entry had been examined using ESDA (see column “D% After ESDA”). Finally, for each known dated entry, one SLRM test (one-step extraction procedure) was conducted before the entry was examined using ESDA (see the R% values without asterisks in the column “R% Before ESDA”).
*The R% values indicated with the asterisks in Table 5 were calculated from the raw numerical data when testing ink samples using the SET12 (i.e., for each known dated entry, the abovementioned two ink aging tests were conducted using the two-step extraction procedure for the SET and then, based on the raw numerical data obtained, both D% [see column “D% Before ESDA”] and R% [see the R% values indicated with the asterisks in the column “R% Before ESDA”] ink aging parameters were calculated). As mentioned above, the R% values without the asterisks were calculated when testing ink samples using the one-step extraction procedure of the SLRM (see column “R% Before ESDA”).
Table 6
Outside proficiency testing using five “blind” ink samples (tests conducted by Valery N. Aginsky on April 8–11, 2011).
| Ink No.* | Ink Aging Parameters, R% and D% | Age of Ink | ||||
|---|---|---|---|---|---|---|
| R% | %E | %Et | D% = %E – %Et | Reported Age | Actual Age (Date of writing) | |
| I | 4 | 25.3 | 24.4 | 0.9 | >6 months | 14 months (February 19, 2010) |
| 2 | 30.6 | 28.6 | 2.0 | |||
| II | 3 | 33.1 | 32.3 | 0.8 | > 6 months | 23 months (May 12, 2009) |
| 3 | 32.8 | 30.4 | 2.4 | |||
| III | 5 | 32.9 | 29.7 | 3.2 | > 6 months | 38 months (February 15, 2008) |
| 4 | 29.3 | 26.8 | 2.5 | |||
| IV | 4 | 64.0 | 58.6 | 5.4 | < 2 years | 16 months (December 17, 2009) |
| 8 | 66.2 | 60.5 | 5.7 | |||
| V | 7 | 39.8 | 25.0 | 14.8 | < 8 months | 3.5 months (December 29, 2010) |
| 3 | 38.9 | 26.3 | 12.6 | |||
[i] * For each of the five ink entries listed in Table 6, two ink aging tests were conducted using the two-step extraction procedure for the SET and then, based on the raw numerical data obtained, both D% (see column “D% 5 %E 2 %Et”) and R% (see column “R%”) ink aging parameters were calculated. Based on this author’s experience, for each of the five inks, the repeatability of the D% and R% values obtained was good (e.g., for the D% values, the range was from 0.3%, for ink No. IV, to 2.2%, for ink No. V) and rather typical for the SET and SLRM, respectively.