Katy Harmon

January 30, 2008

The Case of the Stolen Masterpiece

Teacher’s Instructions

Teaching objectives

  • Students obtain a good understanding of forensic techniques used in the chemistry or art forgery lab; students conduct a scientific investigation: make observations, collect and analyze data, and do experiments
  • Students make predictions and perform several color-changing chemical reactions
  • Students learn how energy travels as a wave and how light transmits through different pigments
  • Students compare and contrast human fingerprints and understand why these characteristics differ between individuals
  • Students explain and draw conclusions based on a variety of evidence from a wide source of data

Recommended Grades: 5-8

Estimated Time: 2-3 hours

Key concepts and terms:

Acid: A chemical compound that, when aqueous, is a solution with a pH less than 7

Base: A chemical compound that, when aqueous, is a solution with a pH greater than 7

pH: A test for acidity or alkalinity, measured by the activity of hydrogen: it is equal to the inverse log of the concentration of H+.

Transmittance: The fraction of light transmitted through a sample

Wavelength: The distance between two wavecrests.

Electromagnetic Spectrum: A range of radiant energies or wave frequencies

Ultraviolet Radiation: Invisible wavelength of light shorter than violet light but longer than radio waves

Fluorescent: emission of light from a substance when acted on by radiant energy (like UV light).

Relationship between color and wavelength: Longer wavelengths of light have lower energy, i.e. red has a long wavelength, whereas violet has a shorter wavelength.

Pigment primary colors: magenta, cyan, and yellow

Procedure

This requires a fair amount of time and extensive preparation. Not every activity needs to be completed, and each can function adequately on its own. Remind students, especially in a scientific setting, that safety always comes first in a chemical investigation.

Ocean Optics Computer Simulation

  1. Again, using the five solutions, instruct students to pipette enough of each solution into a labeled cuvette (there should be five cuvettes, labeled 1-5 on the side)
  2. Using the Ocean Optics Spectrophotometer and LoggerPro, plot the % Transmittance vs. the Wavelength (as per the instructions on materials below). Print out five sheets (one for each solution) and have students record the results on Worksheet 1. If there are a minimum number of students, you can print out a sheet for each student.
  3. Let students predict what solution is what, according to the charts following Worksheet 1.

Pigment Lab

  1. Give students the five solutions to observe. Help them to use an eyedropper to put a little of each solution in one well of a clear plastic spot plate. Have them draw and label the spot plate on Worksheet 2. Stress the importance of using a new eyedropper or pipette for each solution.
  2. Using the eyedropper, have each student test a little drop of the liquid on pH paper. Have them record whether the liquid is an acid or a base.
  3. Allow students to add vinegar dropwise into each well until the liquids are at least slightly acidic (as per instructions on materials below).
  4. Let students use a spoon and carefully scoop a few ferrocyanide crystals into each well of their spot plate. Have them document any changes they observe.

The Masterpiece Detective

  1. Before you begin this activity, talk to students about safety again. When people get suntanned too often, they often get skin cancer and other diseases because of the sun’s harmful UV rays. That’s why we wear sunscreen. The students will be working with a UV light called a black light. It is important that they don’t look at the light, shine it on themselves or friends, or accidentally leave it on. Remind them why they have goggles.
  2. Have students observe the paintings using the UV light one at a time. Ask them to record what they noticed under the UV light on Worksheet 3
  3. Have students draw a picture of their own using glow-in-the-dark paints, chalk and crayons. What glows best under the black light? Explain a bit about fluorescence and why this works.

Caught Blue-handed

  1. Have students observe the fingerprints of both the caretaker and the “historic” fingerprints of Alfredo Fettuccini. Then have them observe fingerprints on the back of the paintings. What physical similarities do they notice? (shape, size, color).
  2. Allow them to get their own fingerprints on the sheets attached below. This can be done with ink, which will wear away with time or rubbing alcohol, or with pencils. For the pencils, have each student scrub a blank piece of paper with the pencil. Then have them rub their fingers over the dark marks. Put a piece of clear tape over the finger and tape it to the fingerprint sheet. Are everyone’s fingerprints the same size? What differences do they notice?

If all activities are completed (and you still have some time), hand out or have them complete Worksheet 4

The Case of the Stolen Masterpiece

Materials List

The Pigment Lab (if in a scientific setting)

  • Blue colored solutions in air-tight containers labeled as follows:

Pigment 1: Pigment from the “Masterpiece” Ebenezer found (1 M Iron (III) Nitrate (Fe(NO3)3) with ~15 ferrocyanide crystals)

Pigment 2: Pigment from a modern painting (Windex)

Pigment 3: Pigment found on the floor of the museum (Water + blue food coloring; should look like pigment 4)

Pigment 4: Pigment from a preserved brush of Fettuccini (Benedict’s solution)

Pigment 5: Pigment stain found on Ebenezer’s overalls (1 M Iron (III) Nitrate (Fe(NO3)3)

  • Potassium ferrocyanide crystals labeled “Indicator”
  • 0.002 M Acetylsalicylic acid labeled “ASA”
  • White vinegar labeled “Acid”
  • pH paper
  • Eyedroppers or plastic pipettes
  • Clear plastic spot plates
  • Worksheet 1

The Pigment Lab (if in a classroom setting)

  • Yellow colored solutions in air-tight containers labeled as follows:

Pigment 1: Pigment from the “Masterpiece” Ebenezer found (lemon juice)

Pigment 2: Pigment from a modern painting (shampoo + yellow food coloring)

Pigment 3: Pigment found on the floor of the museum (Water + blue food coloring; should look like pigment 4)

Pigment 4: Pigment from a preserved brush of Fettuccini (baking soda + yellow food coloring)

Pigment 5: Pigment stain found on Ebenezer’s overalls (Vinegar + yellow food coloring)

  • Red cabbage juice labeled “Indicator”
  • pH paper
  • Eyedroppers of plastic pipettes
  • Clear plastic spot plates
  • Worksheet 1B

The Ocean Optics Computer Simulation

  • Computer with Ocean Optics LoggerPro Software installed
  • Spectrophotometer
  • Cuvettes that fit spectrophotometer
  • Eyedroppers or plastic pipettes
  • Worksheet 2

The Masterpiece Detective

  • 2 paintings or drawings labeled as follows:

Painting 1: the “Masterpiece” Ebenezer found (add ink fingerprints of “Ebenezer” on the back).

Painting 2: An authentic painting by Fettuccini (add some touches of glow-in-the-dark paint, and ink fingerprints of “Fettuccini”).

  • A black light
  • Glow-in-the-dark crayons, chalk or paint
  • Worksheet 3

Caught Blue-handed

  • The 2 paintings or drawings
  • Set of fingerprint sheets
  • Blue or red ink, or pencils, paper, and tape
  • “Ebenezer” fingerprint sheet completed
  • A sheet of paper with “Fettuccini” fingerprints
  • Glow-in-the-dark crayons, chalk or paint

Non-essential Materials:

  • Clipboards
  • Lab coats
  • Goggles
  • Gloves
  • Paper towels
  • A “reward” as thanks from the Art Museum
  • Rubbing alcohol

If all three activities are completed, Worksheet 4 may also be used.

Name ______

Date ______

The Case of the Stolen Masterpiece

Last Friday, a priceless masterpiece was stolen from the little-known Waterville Museum of Old Weird Art. The painting was the masterpiece of the great Italian finger painter, Alfredo Fettuccini. However, yesterday the caretaker told police he forgot he had taken the painting home to clean it, and found it in his bedroom the next morning. An original painting by Fettuccini and the painting produced by the caretaker have been confiscated, packaged, and sent to the Colby Chemistry Lab for analysis.

You suspect that the caretaker, Ebenezer Wheezingeezer, stole the real painting and replaced it with a fake. The Art Museum has heard about your chemistry smarts and genius-level intelligence, and has hired you and some of your classmates to do a little detective work. You will investigate the pigments used in the paintings and then look for clues on the paintings themselves. The Waterville Museum of Old Weird Art has granted you special permission to handle these rare paintings. The police are standing by, awaiting your judgment.

A technician in the chemistry lab will be helping you with your assignment. Your first job is to make sure you and your friends are safe. Today you will be handling some hazardous chemicals and using a dangerous wavelength of light. Make sure you are wearing safety glasses, and ALWAYS ask before you touch something. And most importantly, LISTEN TO YOUR INSTRUCTOR!

Good Luck.

Pigments

Pigments are substances that adsorb certain wavelengths of light. A pigment usually starts out in powdered form and is added to a colorless material called a vehicle before it is used for painting. There are many types of pigments, but not all are used now. For example, blue pigments that contain copper were used before the 1800s, while blue pigments that contain iron are used in modern times. By proving a “masterpiece” has blue paint with iron in it, paint chemists have jailed criminal artists who produce counterfeits, which can sell for millions.

Wavelengths

When you hear “wavelengths of light,” you’re hearing a referral to the visible range of the electromagnetic spectrum. The electromagnetic spectrum is a range of energy, energy which includes visible light (all the colors of the rainbow) as well as radio waves, microwaves, and X-rays.

Light is actually a tiny piece of this spectrum…it’s actually a wave! Red light has the lowest energy, while violet light has the highest energy.

Transmittance

Transmittance just means how much light can pass through a substance. With the spectrophotometer, we will measure how much of every color of light can pass through the liquefied pigments (over a large range of wavelengths).

If a pigment is blue, blue wavelengths will reflect

off the substance, but green and red wavelengths

of light will be absorbed by the substance. Our

eyes see the reflected light, so we see the pigment

is blue.

References:

  1. Millard, J. Adventures in Chemistry. 2006. Ch. 17.

Worksheet 1 – Computer Simulation

Using Ocean Optics Spectrophotometer software to determine transmittance information about each pigment, plot the peaks on the blank graphs below. Read the instructions next to the computer. Katy and Sarah will answer any questions.

Pigment 1

______

Pigment 2

______

Pigment 3

______

Pigment 4

______

Pigment 5

______

Ocean Optics Instructions:

  1. A program called LoggerPro should be open on the computer. Take one cuvette and fill it 2/3 full with distilled water.
  1. Set the cuvette properly in the spectrophotometer. Ask Katy or Sarah to check it for you.
  1. On the toolbar at the top of the screen, select Experiment. Scroll down to Calibrate… and select Spectrometer: 1
  1. When the window pops up, select Skip Warmup. Select Finish Calibration, then wait for a few minutes until the OK button can be selected. Click OK.
  1. Using a pipette, fill a new cuvette 2/3 full with your pigment (1, 2, 3, 4 or 5). Place it properly in the spectrophotometer, and select.
  1. A peak will show up on your screen. Select . Then draw the peak you see.
  1. Compare your data with your classmates. Draw each peak carefully on your worksheet. Then, compare your peaks to the printouts of known spectrophotometric data. If you can identify the pigments, write the name of the paint beneath the peaks you drew on the worksheet.

Pigment 1: Pigment from the “Masterpiece” Ebenezer found

Pigment 2: Pigment from a modern painting

Pigment 3: Pigment found on the floor of the museum

Pigment 4: Pigment from a preserved brush of Fettuccini

Pigment 5: Pigment stain found on Ebenezer’s overalls

Prussian blue

Cerulean blue

Blue watercolor

Azurite blue

The Pigment Lab: Instructions

1. Use a dropper and put 1 drop of each mystery pigment on a pH test strip. Record which ones are acids and which are bases.

2. Add 10 drops of each mystery pigment to 5 different wells. Use a dropper to add 5 drops of acid to the pigments that you determined to be bases. Then, test on the pH strips again. If any pigments are still basic, add five more drops of acid.

3. Once every pigment in the spot plates has been acidified, take a scooper and add 1 small scoop of indicator crystals to each well.

If a pigment has iron in it, it will turn dark blue.

If a pigment has copper in it, it will turn brick red

Since all the pigments are blue to begin with, it may be difficult to know for certain if the pigment has iron in it. If you think you see some of the crystals turn darker, however, you will do an additional test for iron.

4. In 2 new wells in the spot plate, add 3 drops of ASA.

5. Select two pigments that you think turned dark blue when you added indicator crystals. Add 5 drops of each into the wells with ASA until you notice a color change. If iron is in the pigment, you will notice a color change.

Worksheet 2 – The Pigment Lab

1. Which pigments were acids? Which were bases?

Pigment 1 ______Pigment 4 ______

Pigment 2 ______Pigment 5 ______

Pigment 3 ______

2. Draw the Spot plate below.

3. Which pigment(s) turned brick red when you added the indicator crystals?

4. Which pigment(s) turned dark blue when you added the indicator crystals?

5. Did the pigments listed above change color in the ASA?

Worksheet 2B – The Pigment Lab

1. Which pigments were acids? Which were bases?

Pigment 1 ______Pigment 4 ______

Pigment 2 ______Pigment 5 ______

Pigment 3 ______

2. Draw the Spot plate below.

3. Which pigment(s) turned red when you added the indicator liquid?

4. Which pigment(s) turned blue when you added the indicator liquid?

5. Was the pigment that the original artist used and the pigment on the masterpiece the caretaker “discovered” the same?

The Pigment Lab: Instructions II

1. Use a dropper and put 1 drop of each mystery pigment on a pH test strip. Record which ones are acids and which are bases.

2. Add 10 drops of each mystery pigment to 5 different wells.

3. Once every pigment in the spot plates has been acidified, add a few drops of the indicator liquid to each well.

If a pigment has iron in it, it will turn red

If a pigment has copper in it, it will turn blue

Art Undercover

Old pieces of art change over time. Parchment, paper, and canvas can degrade, pigments and inks fade, and weathering can even cause ornate statues to slowly

dissolve, erasing recognizable

features. But most people don’t

like the idea of “painting over”

famous works of art, like Da Vinci’s Mona Lisa or Munch’s

The Scream. So how do museums keep paintings looking good?

In fact, paintings are retouched every so often, but the profess-

-ionals who do are extremely well trained. On famous works of art, each change to the painting must be completely

reversible, and must be obviously

not an original part of the painting.

But how can you tell if the paint is

new? Every change is marked

with fluorescent paint. This paint glows under ultra-violet (UV) light, so that anyone with a black light can see the changes that have been made. If a painting is relatively recent, it will not glow under UV light. However, old masterpieces in all art museums will shine with a fluorescent glow because of the special varnishes used. So how can this help solve the mystery? Well, if both paintings are genuine, they will both glow under a black light. If not, however, it will give us concrete evidence for the police that the painting that doesn’t glow is a fake.

References:

  1. Millard, J. Adventures in Chemistry. 2006. Ch. 17.

Worksheet 3 – The Masterpiece Detective

1. Describe what you saw when you looked at the paintings under UV light:

______

______

______

______

2. Which painting hasn’t been touched up by the special art varnish? (Circle one).

Painting 1Painting 2

3. Try painting with the glow-in-the-dark paints and looking at them with the black light. Is this kind of fluorescence different than what you saw on the paintings? Paint in the space below.

Worksheet 4 – Case Closed!

A. Computer Simulation

1) What number pigment looked like Azurite blue? ______

2) Did any pigments look like Prussian blue? ______

B. The Pigment Lab

1) What metal was in the pigment that the original artist used? ______