Chemistry for Everyone
Crime Scene Investigation in the Art World: The Case of the Missing Masterpiece Katharine J. Harmon, Lisa M. Miller, and Julie T. Millard* Department of Chemistry, Colby College, Waterville, ME 04901; *
[email protected] Chemistry experiments involving mock crimes can effectively engage students of all ages, capitalizing on the popularity of television dramas such as CSI: Crime Scene Investigation (1). Many such examples have been described recently both in this and other educational journals (2–12). Another widely appealing aspect of chemistry is its relationship to color (13, 14) and painting (15–18). We describe an outreach activity suitable for middle- and high-school students that combines the chemistry of crime with the chemistry of art. This multi-part exercise was designed to enhance the classroom science experience while covering required state-mandated science goals for given age levels (19), including familiarity with the changes that matter can undergo, an understanding of electromagnetic radiation, and application of inquiry and problem-solving approaches in science. Such fundamental principles are common educational goals at the middle- and high-school level and are consistent with National Science Education Standards (20). Furthermore, the engaging theme of this exercise promotes a core educational precept (19): Helping students develop curiosity and excitement for science and technology while they gain essential knowledge and skills is best achieved by actively engaging learners in multiple experiences that increase their ability to be critical thinkers and problem solvers.
We designed and implemented this activity as part of a previously described service-learning course (21), both in our own laboratories on campus and in classrooms at the local middle school (~100 students total). We also successfully incorporated this exercise in a non-majors college laboratory course, demonstrating its wide appeal across many age groups. Depending on the age group, the activity takes 1.5 to 2 hours. Learning Goals Our exercise was designed to achieve the following learning goals. Students (i) gain an understanding of forensic techniques used in the analysis of paintings; (ii) conduct a scientific investigation: make predictions and observations, do experiments, and collect, analyze, and interpret data; (iii) learn how energy travels as a wave and how light is absorbed by different pigments; and (iv) perform several color-changing chemical reactions. Laboratory Activity The premise for the experiment is that a priceless painting has been reported stolen from a local art museum. After police are called in to investigate the crime, the caretaker reports that he had actually removed the painting for cleaning. He produces a painting that he claims is the missing masterpiece, but there is
some suspicion that he may have substituted a forgery. The goal of this activity is to analyze an original painting by the same artist, the painting in question, and several blue pigment samples relevant to the case to determine whether the recovered painting is genuine. After being briefed on the details of the case, students are given a short overview of pigments and visible light, and they then rotate through the various parts of the experiment, which can be completed in any order. The two major investigative tracks are spectroscopic and chemical analysis of the pigments. Two additional exercises can be used to decrease the size of the working groups, particularly if spectrophotometers are limiting. Each group of students, working in pairs, performs a different part of the investigation and then rotates to the next station. Each activity requires 20–30 minutes for data collection and analysis. In a middle-school environment where close supervision may be required, it is optimal for each station to have its own instructor to oversee that activity. Absorbance and Color The absorbance and color exercises investigate the relationship between the light absorbed by a pigment and its color. The “low-tech” qualitative investigation uses a flashlight passed through different colored filters (red, blue, and green) to determine the absorbances of different colored solutions (yellow, cyan, and magenta). Students observe that a pigment blocks light of its complementary color. The “high-tech” investigation uses a UV–visible spectrophotometer to determine the absorbance spectra for several mock pigments relevant to the crime (including pigments allegedly from a preserved brush of the artist and from the questioned masterpiece, Figure 1). Comparison to reference spectra provided in the handout then allows students to identify these pigments. Although useful painting pigments are generally water-insoluble (22) and therefore require analysis via reflectance of light, we used water-soluble dyes, such as food coloring, and transition-metal salts as our mock pigments. This allowed us to use traditional UV–visible absorbance spectrophotometers for analysis. Instead, attenuated total reflectance measurements in the infrared, UV, or visible range could be used to analyze paint chips if desired (23). For those with access to them, fiber optic reflection probes that can be coupled to portable spectrophotometers make such measurements feasible in an outreach setting (24). Chemical Analysis In the chemical analysis exercise students test pigment samples for iron and copper ions. Because iron-containing pigments were not available at the time when the artist worked (18), the presence of an iron-containing blue pigment in the questioned masterpiece would be consistent with fraud. These reactions are based on common reactions of cations, including
© Division of Chemical Education • www.JCE.DivCHED.org • Vol. 86 No. 7 July 2009 • Journal of Chemical Education
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Absorbance
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the reaction of potassium hexacyanoferrate(II) [K4Fe(CN)6] with Cu2+ and Fe3+ (Figure 2).
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Art Undercover In the art undercover exercise, students examine a known painting of the artist and the suspected forgery with a hand-held black light. UV light is often used during painting analysis to reveal areas that have been recently altered (22). Modern restorers generally use paints and varnishes that absorb in the UV range and then fluoresce so that restoration is readily detectable. Students look for evidence of restoration in both paintings, as indicated by the presence of fluorescent paint. Lack of fluorescence by the suspected fraud would be suggestive of a modern origin. Although compelling, this exercise is relatively quick, so middle-school students can be provided with fluorescent paints and colored pencils to draw their own pictures for examination under UV light.
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Wavelength / nm Figure 1. Absorbance spectrum of a blue pigment obtained from a preserved brush of the artist (top) is inconsistent with that of a blue pigment obtained from the suspected forgery (bottom).
Examining the Evidence When they have finished the exercises, students complete a final summary worksheet that requires them to review and interpret their data in the context of all the evidence. For middle-school students, this task is best carried out with the entire class to ensure that everyone understands all aspects of the analysis. We observed that students felt an enhanced sense of accomplishment after resolving the case on the basis of multiple investigative steps, which required them to put many pieces of the puzzle together. Any discrepancy among the data can lead to further discussions of real crime laboratories and the need for quality control and rigorous standards. Although we chose to make the evidence suggestive of fraud when we implemented this activity, individual instructors can select pigments appropriately for their preferred outcome. Certainly an innocent suspect would provide a compelling case for the need for objectivity on the part of crime scene investigators (1). Execution at the College Level To assess the versatility of this exercise, we also implemented it with college students in our non-majors laboratory course. Overall, the students ranked its educational value at 3.5 out of 5 and its enjoyment value at 4.3 out of 5. Students commented positively on the exercise’s use of different techniques towards a common goal, its relevance to real life, its use of principles discussed earlier in the course (e.g., acid–base chemistry), and its connection to art. Several students reported that this was their favorite laboratory of the semester. Hazards
Figure 2. Middle-school students (7th graders) perform chemical tests on pigment samples.
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The reagents used in this exercise have minimal toxicity, but students should be instructed in standard chemical safety procedures, such as to avoid ingesting or inhaling any reagents. Students do not handle solid substances, which can pose inhalation hazards, but use only drops of prepared solutions. Potassium hexacyanoferrate(II), chromium(III) nitrate, copper(II) sulfate, and copper(II) chloride may cause irritation to skin, eyes, and respiratory tract. Iron(III) nitrate and dipotassium chromate are oxidizers and may cause fire when in contact with other materials. Eye protection should be worn at all times, and UVprotective goggles should be worn when using the UV lamps.
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Chemistry for Everyone
Acknowledgment We thank the Chemistry 151 students in January 2008 for support and Pam Easler and other area teachers for their participation. Literature Cited
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Bergslien, E. J. Chem. Educ. 2006, 83, 690–691. Beussman, D. J. J. Chem. Educ. 2007, 84, 1809–1812. Henck, C.; Nally, L. J. J. Chem. Educ. 2007, 84, 1813–1815. Hartzell-Baguley, B.; Hipp, R. E.; Morgan, N. R.; Morgan, S. L. J. Chem. Educ. 2007, 84, 689–691. Hoffman, E. M.; Beussman, D. J. J. Chem. Educ. 2007, 84, 1806–1808. Jackson, D. D.; Abbey, C. S.; Nugent, D. J. Chem. Educ. 2006, 83, 774–776. Saccocio, L. A.; Carroll, M. K. J. Chem. Educ. 2006, 83, 1187– 1189. McNamara-Schroeder, K.; Olonan, C.; Chu, S.; Montoya, M. C.; Alviri, M.; Ginty, S.; Love, J. J. Biochem. Mol. Biol. Educ. 2006, 34, 378–383. Millard, J. T.; Pilon, A. M. J. Chem. Educ. 2003, 80, 444–446. Bender, S.; Lillard, S. J. J. Chem. Educ. 2003, 80, 437–440. Kniesel, A.; Bellamy, M. K. J. Chem. Educ. 2003, 80, 1448– 1450. Carson, T. M.; Bradley, S. Q.; Fekete, B. L.; Millard, J. T.; LaRiviere, F. J. J. Chem. Educ. 2009, 86, 376–378. Stevens, K. E. J. Chem. Educ. 2006, 83, 1544–1545. Mihalick, J. E.; Donnelly, K. M. J. Chem. Educ. 2006, 83, 1550– 1551.
15. Orna, M. V. J. Chem. Educ. 2001, 78, 1305–1311. 16. Kafetzopoulos, C.; Spyrellis, N.; Lymperopoulou-Karaliota, A. J. Chem. Educ. 2006, 83, 1484–1488. 17. Uffelman, E. S. J. Chem. Educ. 2007, 84, 1617–1624. 18. Ware, M. J. Chem. Educ. 2008, 85, 612–620. 19. Department of Education, State of Maine, Learning Results for Science and Technology. http://www.maine.gov/education/lres/ st.htm (accessed Mar 2009). 20. The National Academies Press, National Science Education Standards. http://www.nap.edu/openbook.php?record_ id=4962&page=106 (accessed Mar 2009). 21. LaRiviere, F. J.; Miller, L. M.; Millard, J. T. J. Chem. Educ. 2007, 84, 1636–1639. 22. Millard, J. T. Adventures in Chemistry; Houghton Mifflin Company: Boston, 2008; pp 603–632. 23. Derrick, M. R.; Stulik, D.; Landry, J. M. Infrared Spectroscopy in Conservation Science; Getty Conservation Institute: Los Angeles, 1999; pp 148–171. 24. Ocean Optics Reflection Probes. http://www.oceanoptics.com/ Products/reflectionprobes.asp (accessed Mar 2009).
Supporting JCE Online Material
http://www.jce.divched.org/Journal/Issues/2009/Jul/abs817.html Abstract and keywords Full text (PDF) Links to cited URLs and JCE articles Supplement Detailed instructions for the students
Notes for the instructor
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