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 Table of Contents  
Year : 2018  |  Volume : 4  |  Issue : 4  |  Page : 197-202

Is magnetic flux a valuable tool for the analysis of electrophotographic-printed documents?

1 Ecole des Sciences Criminelles, Faculty of Law, Criminal Justice and Public Administration, Université de Lausanne, Lausanne, Switzerland
2 Key Laboratory of Evidence Law and Forensic Science, Ministry of Education, Institute of Evidence Law and Forensic Science, China University of Political Science and Law, Beijing, China

Date of Web Publication27-Dec-2018

Correspondence Address:
Dr. Williams David Mazzella
School of Criminal Science, University of Lausanne, Lausanne
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jfsm.jfsm_31_18

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The goal of this preliminary study was to evaluate the potential application of magnetic flux for document screening. In this investigation, we examined the homogeneity of magnetic flux over the entire page of sample documents and provided recommendations on the measurements procedure.

Keywords: Black toner, electrophotographic printing system, magnetic flux, magnetism

How to cite this article:
Mazzella WD, Li B. Is magnetic flux a valuable tool for the analysis of electrophotographic-printed documents?. J Forensic Sci Med 2018;4:197-202

How to cite this URL:
Mazzella WD, Li B. Is magnetic flux a valuable tool for the analysis of electrophotographic-printed documents?. J Forensic Sci Med [serial online] 2018 [cited 2022 Sep 27];4:197-202. Available from: https://www.jfsmonline.com/text.asp?2018/4/4/197/248698

  Introduction Top

The analysis of toners and electrophotographic printing systems is well-documented in forensic literature, and as such, a review of these systems is not performed in this report. Instead, we only focus on magnetic analysis.

Magnetic analysis facilitates quantitative measurements and has been extensively explored by Herlaar,[1] Biedermann et al.,[2] and Polston et al.[3] Herlaar et al. studied 72 printed samples from 19 different laser printers using magnetic toner. In this study, it was demonstrated that magnetism can potentially allow for the discrimination between different printers. The results of the investigation by Biedermann indicate that the analysis of magnetism is complementary to traditional methods such as FTIR for the analysis of black toners. Further, it was determined that the analysis of magnetism can be reasonably applied in closed set cases, that is, when the number of potential printing devices can be clearly defined. Biedermann noted that documents of a given case should be examined by the same operator. Polstonwas able to demonstrate that magnetic flux could be correlated to the toner area, which allows for the normalization of results and the comparison of documents with different printed content. It was determined that, in general, there is sufficient variation in toner population to allow for discrimination.

The main shortcoming of the research by Biedermann and Polstonis that the authors performed their measurements on one single area of a printed A4 format document. In this investigation, the distribution of magnetic properties across an entire A4 document has been performed.

  Material and Methods Top

Analysis of magnetic properties

This report focuses only on single-component toner powders (or monocomponent toners) that contain ferrous material incorporated into the toner particles, which when fixed onto paper, exhibit magnetic properties similar to other forms of magnetic printing. The magnetic properties, particularly the magnetic flux (nWb), were measured using the Regula Magmouse Model 4197. All the measurements with this magneto-optical visualizer were performed using the same standard procedure, that is, all the samples used in this study were measured at the same location on the same wooden table.

Printed samples and magnetic toner tested

To verify the homogeneity of the magnetic flux across an A4 format page, a master document was printed using a Canon iR C5255i multifunction printing system. The master consisted of the same repetitive text [Figure 1], which almost corresponds to the measurement area (14 mm × 18 mm) of the Regula Magmouse Model 4197. The printed master was then photocopied using a Canon PC 1230D multifunction system. The first copy was made on November 2, 2017, using an original Canon M11F09Ci old cartridge of toner. On November 9, 2017, the old original Canon toner cartridge was replaced with a new Keymax compatible toner cartridge, and ten copies were made. After printing 200 documents, ten additional copies were made on January 12, 2018. For each copy, 143 measurements were performed. As an internal standard, the previous Canon iR 2230 used in a previous study[2] was measured 11 times.
Figure 1: The printed master used to conduct the research

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Finally, an identical text was printed with four laser printers using magnetic toners, namely, a Canon LBP 3200, a Canon iR 2270, an HP Laser Jet 4000, and a Kyocera KM 3050. The area for the text on each document was measured using the Personal IASLab® software by Quality Engineering Associate Inc., (QEA®), Burlington, USA. All the magnetic flux results presented in this report are in “nWb” unit.

  Results Top

Initially, the mean of the magnetic flux for the measured Canon iR 2230 internal standard varied from a minimum of 15.36 to a maximum of 1600. These values are fully in agreement with the data measured in a previous investigation.[2] The first copy which was made on November 2, 2017, using a Canon M11F09Ci old toner cartridge exhibited an inhomogeneous toner distribution that could be observed with the naked eye in the 10th column [Figure 2]. The inhomogeneous magnetism distribution for the first copy is highlighted in [Figure 3]. The differences in the magnetism are highlighted using a color gradient from green (low values) to red (high values). The measurement of the magnetic flux using the magneto-optical visualizer confirms that it is correlated to the area because column 11 shows the lowest values of magnetism.
Figure 2: The copy made with a Canon M11F09Ci old cartridge of toner showing an inhomogeneous toner distribution (column N° 10)

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Figure 3: The magnetic flux gradient for the copy made with a Canon M11F09Ci old cartridge of toner

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The first copy out of the ten made on November 9, 2017, with a Keymax compatible toner cartridge shows a different magnetism profile [Figure 4].
Figure 4: The magnetic flux gradient for the copy made with a Keymax compatible toner cartridge

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The magnetism profile is similar for samples 4–7 [Figure 5]. To investigate potential differences between the vertical and horizontal measurements, sample N° 7 was measured in both directions. Sample 7 was first measured column-by-column and then row-by-row. No significant differences of the magnetism were detected based on the direction of measurement [Figure 6].
Figure 5: The magnetic flux gradient for the samples N° 4 (top left) to N° 7 (bottom right)

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Figure 6: The magnetic flux gradient for the samples N° 7 measured column by column (top) and row by row (bottom)

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Despite some absolute differences, the magnetism profile is similar for the samples printed a month apart, during which 200 copies were made [Figure 7].
Figure 7: The magnetic flux gradient for samples printed with a month apart during which 200 copies were made

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The magnetism distribution is also different for the samples printed with the four different laser printers. For these samples, a few measurements of the magnetism were performed in the same positions. [Table 1] shows the magnetism per mm2 measured for the four different printers. For example, the sample printed with the Canon LBP 3200 exhibited a different magnetism compared to the printouts obtained with the Canon iR 2270 and the Kyocera KM 3050 laser printers.
Table 1: Magnetic flux for four laser printers

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  Discussion and Conclusion Top

Magnetic flux measurements are a valuable tool for toner discrimination and should be used as a preliminary test. However, the result of this descriptive qualitative research indicates that the magnetic flux is not homogeneous across an entire A4-printed page. However, the magnetic flux distribution is similar from page to page for the same printing system. This similarity is observed for samples printed 1 month apart. The main reasons that may account for the inhomogeneous magnetic flux are as follows:

  • The toner ferrous material in the cartridge is not uniformly distributed (i.e. the toner is not shaken before use)
  • The corona charging of the organic photoconductor (OPC) drum is not uniform
  • The organic coating of the OPC drum is not uniform
  • A combination of the three previous explanations.

Based on the aforementioned list of possibilities, it is imperative that when different documents are examined, the magnetic flux should be measured in the same position for each printed document. This was successfully measured during the Collaborative Testing Services, Forensic Testing Program Test No. 16-521.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Herlaar K, Mieremet M, Fakkel M. Measuring magnetic properties to discriminate between different laser printers. J Am Soc Questioned Doc Examiners 2016;18:51-66.  Back to cited text no. 1
Biedermann A, Bozza S, Taroni F, Fürbach M, Li B, Mazzella WD, et al. Analysis and evaluation of magnetism of black toners on documents printed by electrophotographic systems. Forensic Sci Int 2016;267:157-65.  Back to cited text no. 2
Polston C, Mazzella W, Fuürbach M, Buzzini P. Evaluating Magnetic Flux as a Screening Tool for Toner Printed Documents. 75th Annual Meeting of the American Society of Questioned Document Examiners. San Diego, USA; August 2017.  Back to cited text no. 3


  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]

  [Table 1]

This article has been cited by
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2 The assessment of the impact of induction spatial effects on magnetic flux measurements of toner-printed documents to the detection of forged or altered documents
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