National Chemistry Week 2001

Transcription

1 State of the Art Chemistry: A Hands-on Program An Educational Demonstration Package Prepared by the Cleveland Section of the American Chemical Society National Chemistry Week 2001 Overview Celebrate National Chemistry Week by exploring the world of art through the eyes of a chemist! This year s demonstrations encourage participants to act as museum curators with the task of distinguishing between "authentic" and "replica" pieces of artwork and other artifacts. Students will learn about paper, ink, paint, ceramic, metals, fabric, and other mediums used by artists as they conduct hands-on experiments based on the chemistry and science of these materials.

2 Table of Contents Page Check-Lists 4 Experimental Setup 6 Opening Session 10 Closing Session and Clean-Up 30 Appendix 31 Acknowledgements The National Chemistry Week (NCW) programs of the Cleveland Section ACS began in 1994 with an idea to put together a scripted program that could be performed at any local school or library. This idea has expanded to become the centerpiece of Cleveland Section's NCW activities, which has received national recognition from the American Chemical Society. In 2001, the Cleveland Section volunteers will perform nearly sixty demonstrations at libraries, schools, and other public sites. New this year, the Cleveland Section will also be providing training and materials for Cleveland-area teachers (at the Cleveland Regional Council of Science Teachers Fall Conference) so that they can conduct additional programs in their own classrooms. This library/school program and other NCW events are the result of the hard work of many dedicated and talented volunteers. It all starts with our local section NCW Planning Committee. The Committee develops a theme for the program; recommends, tests, and reviews activities & experiments; writes a script; collects supplies and materials; prepares the kits; recruits sponsors and volunteers; contacts libraries and schools; and schedules shows. This Committee, as well as the rest of the Section's NCW activities, are overseen by the Cleveland Section's NCW coordinators, Paula Fox and Kat Wollyung. Committee members include Shermila Singham, Lois Kuhns, Helen Mayer, Marcia Schiele, Rich Pachuta, Fen Lewis, Betty Dabrowski, Mike Setter, Mark Waner, Peggyann Moore, Don Boos, and Maria Lopez. Additional credit and thanks is given to Kat Wollyung for writing this year's script and to all of the unnamed GAK (Grand Assembly of Kits) Day volunteers who gave a Saturday in October to help count, measure, and assemble all of the necessary materials for our demonstration kits. Our NCW efforts reach farther this year because of various sponsors who have donated money, materials, and/or services to the Cleveland Section specifically for National Chemistry Week. We are especially grateful to NASA Glenn Research Center, John Carroll University, Allegheny Rodney (Ivyland, PA), Loctite Corporation, Alice's Ceramics (Austinburg, OH), and Wal-Mart (Brooklyn Store) for their numerous contributions and support. Last and most important, we thank all the volunteers who donate their time and expertise. Without the dozens of dedicated chemical professionals to lead these activities, there would be no Cleveland Section NCW program. National Chemistry Week Cleveland Section 2

3 How Experiment Write-ups are Organized Overview The materials and set-up of the demonstrations are located in the introduction section of this packet. Then, each experiment write-up is presented as follows: Background Information for Demonstrators Demonstration Instructions Experiment Conclusions Additional Information If Needed Presentation Overview This section describes the basic presentation technique used during the demonstrations. This is a guideline only as the technique may vary for some experiments. Make sure you follow the instructions given in each experiment. 1. Introduce experiment. 2. Do your demonstration piece. Note: 3. Have the students do their experiment. Note: work Most experiments require you to perform the experiment to show the students what to do on their own. For some experiments your demonstration and the students hands-on are nearly simultaneous. You are leading them as they perform the experiment. 4. Some experiments will be done by all students. For others, there will be one experiment that will be shared by all students at the table. In a few cases, only the demonstrator will perform the experiment. You are encouraged to get student helpers for the demonstrator-only experiments. MAKE SURE TO FOLLOW ALL DIRECTIONS IN EXPERIMENTS Some experiments have special safety concerns due to the materials being used. Any safety concerns are listed in the section for that experiment. Material Safety Data Sheets for the chemicals used in this program are provided in the Appendix A. National Chemistry Week Cleveland Section 3

4 Check-Lists Demonstration Check-Off List The next few pages list suggested activities to complete for the program. Activities To Do Before the Day of the Demonstration When Complete Read through this packet to familiarize yourself with the experiments Collect the materials you need to bring with you to the demonstration. The materials list begins on page 6. Contact the children s librarian: Ask the room to be arranged with 6 tables around a front table Ask to have 5 chairs around each of the 6 tables Ask for all the tables to be covered with newspapers and for extra paper towels for each table. Ask about availability of demonstration materials from list on page 6 (ex. water, paper towels, extension cord) Make sure that the room is available before and after the program for set up and clean up. Activities To Do When You Get To The Library When Complete Arrive approx. 1 hour before demo time to allow for set up Introduce yourself to the children s librarian Ask the librarian how many students are pre-registered Confirm that the tables and chairs are set up properly Confirm that all tables are covered in newspaper and have paper towels Obtain any additional supplies (from list on page 6) if provided by library Complete Demonstration Set-Up for all demonstrations: (see Activities to Do On-Site Prior to Demonstration on page 8 and 9) Note: This set-up is estimated to take minutes. Set out the literature (Experiments To Do at Home, Book List, ChemMatters magazines, and NCW Activities newspapers) National Chemistry Week Cleveland Section 4

5 Check-Lists Activities To Do During The Demonstration Timing Welcome the students and parents as they enter the room - Assess number of students per table and adjust to 3-5 per table. Record the number of students and adults on the Feedback Form. - Complete the Opening Session introduction and distribute the goggles 5 min. Perform demonstrations Total Time: 55 min. Experiment 1: Older Metal Aluminum vs. Stainless Steel 5 min. Experiment 2: Paint Prussian Blue 10 min. Experiment 3: Papers and Inks Chromatography & Fluorescence 10 min. Experiment 4: Frames glass vs. polycarbonate 3 min. Experiment 5: Fabric Identification with Powdered Drink Mixes 10 min. Experiment 6: Ceramic or Plaster of Paris 5 min. Experiment 7: Take-Home Activity Clay Art Objects 7 min. Complete the Closing Session information, collect goggles, and hand out literature 5 min. Activities To Do Immediately After The Demonstration When Complete Clean up as indicated in the Clean up section, including sanitation of goggles if you will be re-using them for another library program Give any left-over literature to the librarian Give the following materials to the librarian to be returned by interlibrary mail: demo survey sheet, goggles (in box), UV light (in cardboard sleeve) National Chemistry Week Cleveland Section 5

6 Experimental Setup Supplies Required for Demonstration (*For details, see Appendix.) Items for the Demonstrator to Provide 1 gallon jug for waste collection 1 large garbage bag for waste collection, if none at site 1 gallon jug of water, if none at site 1 roll paper towels, if none at site newspaper for covering tables, if none at site extension cord (for UV light), if none at site objects (shells, leaves, small stones, coins, etc.) to imprint in clay small quantity of household bleach (for sanitizing goggles) wash bin or bucket (for sanitizing goggles) rags or old towels (for sanitizing goggles) General: 1 demo survey sheet and envelope 1 sheet Authentic 1 sheet Replica 6 sheets Authentic/Replica 30 copies NCW activity newspapers 30 copies each of Book List / Experiments To Do at Home and Chemical Origami 10 copies of ChemMatters magazine goggles* (30 child size and 2 adult size) Experiment 1: Older Metal: Aluminum vs. Stainless Steel 10 ml 0.5 M copper (II) sulfate with NaCl in vial marked CuSO 4 or Cu solution 31 aluminum pieces in zipper bag marked Al 31 stainless steel foil pieces in zipper bag marked ss 7 disposable plastic pipets 7 plastic opaque 3-oz. cups Experiment 2: Paint Prussian Blue 40 ml ferric chloride hexahydrate (FeCl 3.6H 2 O) solution in vial marked A 40 ml potassium ferrocyanide (K 4 Fe(CN) 6.H 2 O) solution in vial marked B 10 ml 0.1 M NaOH in vial marked NaOH 15 grams calcium carbonate in zipper bag marked CaCO 3 1 plastic spoon 7 craft sticks 7 paper cups, 3-oz. 7 opaque plastic 3-oz. cups marked A 7 clear plastic 5-oz. cups marked B 1 disposable plastic pipet 7 authentic test pieces in zipper bag marked Auth. National Chemistry Week Cleveland Section 6

7 Experimental Setup 7 replica test pieces in zipper bag marked Rep 31 cotton swabs 31 half-sheets of white paper Experiment 3: Papers and Inks Chromatography and Fluorescence 1 sketch on authentic paper 1 sketch on replica paper (fluoresces with UV light) 31 authentic paper test samples in zipper bag marked Auth 31 replica paper test samples in zipper bag marked Rep 7 tall plastic cups (9 oz) ** NOTE: YOU MAY HAVE SHORTER CUPS AND MAY NEED TO ADJUST YOUR EXPERIMENTAL PROCEDURE SLIGHTLY 7 chromatography strips with old/authentic ink dot 7 chromatography strips with new/replica ink dot UV light in cardboard sleeve extension cord if needed water paper towels Experiment 4: Frames (glass vs. polycarbonate) 7 glass slides in zipper bag marked glass 7 polycarbonate slides (with corner peeled) in zipper bag marked poly UV light, extension cord, and new paper samples from Expt. #3 Experiment 5: Fabric Identification with Powdered Drink Mixes as Dyes 3 packages Kool-Aid, 1 each of cherry, orange, and grape 9 cocktail-style plastic cups 27 silk swatches (2 x 2 ) in zipper bag marked silk 9 polyester swatches (2 x 2 ) in zipper bag marked poly 3 multi-fiber ribbon pieces 1 9 plastic forks paper towels 1 quart water Experiment 6: Ceramic or Plaster of Paris 1 bag of ceramic pieces marked A (authentic) 1 bag of plaster pieces marked B (replica, marked with a green dot on the corner) 10 ml 5% HCl solution in vial marked HCl 1 disposable pipet Experiment 7: Take-Home 1 bag of homemade clay 31 paper plates National Chemistry Week Cleveland Section 7

8 Experimental Setup 31 toothpicks objects to imprint as supplied by demonstrator National Chemistry Week Cleveland Section 8

9 Activities to Do On-Site Prior to Demonstration General: Place one Authentic/Replica sheet on each of the students tables Place the Authentic and Replica sheet on the demonstrator s table Experiment 1: Older Metal: Aluminum vs. Stainless Steel Experimental Setup Distribute the blue copper (II) sulfate, sodium chloride solution into the 7 small cups. Place one cup of copper solution and one disposable pipet onto each of the student tables. Place 5 pieces of aluminum foil and 5 pieces of stainless steel foil onto each of the student tables; BE SURE to keep the two piles separated! Place one cup of copper (II) sulfate solution, one pipet, one aluminum piece, and one ss piece on the demonstrator s table. Experiment 2: Paint Prussian Blue Distribute solution A into the 7 opaque 3-oz cups marked A ; place one cup on each table. Distribute solution B into the 7 clear 5-oz cups marked B ; place one cup on each table. Use the plastic spoon to divide the CaCO3 evenly between the 7 paper cups; place one on each student table and one on the demonstrator s table. Place 5 cotton swabs, one craft stick, 5 half-sheets of white paper, one authentic canvas, and one replica canvas on each student table. Place one cotton swab, one craft stick, one half-sheet of paper, one authentic canvas, one replica canvas, the pipet, and the NaOH solution on the demonstrator s table. Experiment 3: Papers and Inks Chromatography and Fluorescence Pour approx. _ inch of water (the elution solvent) into each of the cups, and distribute them among the 7 tables. Make a gentle fold (lengthwise) in the chromatography paper samples (this will help them stand better in the cups). Place 5 authentic papers and 1 authentic pen-marked strip on each of the student tables. Place 5 replica papers and 1 replica pen-marked strip onto each of the student tables, making sure not to mix up the two piles. Place one paper towel on each of the student tables. Place the authentic sketch, the replica sketch, 1 authentic paper sample, 1 authentic chromatography strip, 1 replica paper sample, 1 replica chromatography strip, a paper National Chemistry Week Cleveland Section 9

10 Experimental Setup towel, and the UV light (with extension cord if necessary) on the demonstrator s table. Experiment 4: Frames Glass vs. Plastic Place 1 glass and 1 polycarbonate sample onto each table. Make sure that the UV light, when plugged in, is able to reach each table. Experiment 5: Fabric Identification with Powdered Drink Mixes Prepare each of the powdered drink mix dye solutions by dissolving a packet in 100 ml of water. (A line has been drawn at the 100 ml level on one of the cups to make measuring easier.) *This can be done at home, prior to the demonstration and stored in small bottles.* Divide each of the prepared dye solutions among three of the cocktail cups. Place a set of all three dyes on the demonstrator s table. Distribute the other cups of dye among the student tables so that each table has one cup of dye. Put 4 swatches of natural silk fiber fabric, 1 swatch of synthetic polyester fiber fabric, a paper towel, and one plastic fork on each student table. Place three pieces of multi-fiber ribbon, three pieces of silk fabric, three pieces of polyester fabric, a paper towel & three forks on the demonstrator s table. Experiment 6: Ceramic vs. Plaster of Paris Place 1 ceramic piece and 1 plaster piece on each student table. Place 1 ceramic piece, 1 plaster piece, the disposable pipet, and the HCl solution on the demonstrator s table. Experiment 7: Take-Home Place 5 paper plates and 5 toothpicks, and a few impressionable objects on each student table. Place 1 paper plate, 1 toothpick, and impressionable objects on the demonstrator s table. Place the bag of homemade clay on the demonstrator s table. (DO NOT distribute the clay to the student tables until just before performing the activity because it will dry out.) National Chemistry Week Cleveland Section 10

11 Opening Discussion Introductions Do the following: Opening Session Introduce yourself as a chemist, and introduce the American Chemical Society as the largest organization in the world devoted to a single profession. Introduce National Chemistry Week - what it is and why we do it. (Hint: it is a nationwide event put on by volunteers like you to let non-chemists know about chemistry and how it has improved our everyday life.) What is Chemistry and Chemicals? Do the following: Explain that chemistry is the study of everything around them. Ask for volunteers to name some chemicals. Then ask more volunteers to name something that isn't a chemical. Remember: everything around us is a chemical. Be very careful in correcting the students. Encourage their participation while explaining that anything they name really is a chemical. What Do Chemists Do? Ask the participants to tell you what a chemist does, what a chemist looks like. Tell them BRIEFLY and in simple terms what you do as a chemist. Note: This should last no more than 1 minute. Remember to leave the physical chemistry lecture and the big chemistry words at home! Tell them that chemists use their knowledge to answer questions about the world around them. This is very exciting, as they will soon see. Introduce Today s Presentation: State of the Art Chemistry Do the following: National Chemistry Week Cleveland Section 11

12 Opening Session Tell the students that many objects that were either tools or art in the past are considered to be art today and have been around for a long time. TIMELINE TIDBITS: 6500 BC - First clay pots & bowls in use 3600 BC - Copper & tin alloyed to make bronze 2640 BC - Silk production begins in China 1200 BC - Egyptians make linen from flax First plastic, called celluloid, invented. One of its commercial uses was to replace the ivory in billiard balls. Tell the students that a very interesting mystery has occurred and you need their help to solve it. Tell the students that they can help by acting as art conservation chemists for the next hour. Art conservation chemists help art conservators and curators understand the materials and methods used by artists to make works of art. They also develop and test new materials and techniques that can help preserve artworks. Sometimes art conservation chemists are called on to determine if the materials used in a work of art are consistent with the object s presumed creation date. In other words, they can determine if the object is authentic or whether it is a replica, or forgery, or contains portions that were altered at some later date. Give them the following background information (provide as much of this information as you are comfortable with): For years, individuals have made replicas of special art pieces. There are many different reasons for making duplicate art pieces. During the Renaissance, it was common for an artist to make an original painting, and then have the students in his workshop make copies. The artist would then sign the various copies himself. It is now believed that at least half of the paintings attributed to the Dutch painter Rembrandt were not actually his own work, but those of his students. Nowadays, such actions would be considered fraud, but at the time, it was common practice. Other types of replicas were due to the nature of the art form. Another Renaissance artist, Albrect Durer, created art from woodcuts. In woodcutting, a block of wood is carved, pressed into paint, and then pressed onto paper (similar to today s rubber stamps). Many pieces of art can be made from the same woodcut. Woodcuts can also be traced back to ancient Egypt, the Roman Empire, and China. In Europe, woodcuts were used for making prayer card for pilgrims, playing cards, simple prints, and block books. (Woodcuts are considered the earliest form of printing). Bronze statues are another form of art that has often created multiple copies. The artist makes a mold for the statue, then casts multiple copies of the mold. The French artist Auguste Rodin s famous Thinker statue was cast several times; copies can be found in New York, Philadelphia, Paris, and other locations. National Chemistry Week Cleveland Section 12

13 Opening Session These days, museum curators might make a duplicate piece so that the original can be protected from damage or so that the item can be displayed in different locations at the same time. Duplicate pieces made for dishonest reasons and passed off as the original, even though they aren t, are called fakes or forgeries. Set-up our the premise to our demonstration program by explaining to the students that a special collection of art objects has been transported to Cleveland for a special display. The collection contains original, or authentic pieces and copies, or replicas that were created to look like the originals. In transit, the various boxes got all mixed up! The replicas look so much like the original authentic pieces, that it is difficult to tell them apart just by looking at them. It is our job as art conservation chemists to determine which of the objects are the originals and which are the copies so that they can be properly labeled and displayed. The good news is that we know many things about the nature of the authentic and replica pieces such as when they were created and what they were made from. We also have some artifact sample pieces that we can use to perform our various tests on. We will use our knowledge of the chemistry of materials to help tell them apart! Tell the students that we will be using the scientific method to guide us in our investigation. We will make observations, form a hypothesis, uses experiments to test our hypothesis, and then evaluate the results of the experiment to accept or reject the hypothesis. Finally, indicate to the students that although we are pretending to be art conservation chemists, we are not testing actual works of art. Art conservationists must be very careful not to do any damage to the artwork that they are testing. Some of the tests that we are doing are destructive and would not be used on actual artwork. The artifact samples that we are using have been created special for our use. (For additional information on tests used by art conservation scientists, see Appendix B.) Introduce the Items on the Tables Do the following: Tell the students that samples of the artifacts have been gathered for them on their table. Tell them not to touch anything until instructed to do so. Remind them never to taste or smell anything, as if they were in a laboratory! A sheet marked Authentic / Replica has also been placed at each table. As we test the various objects, we will be able to sort them into two piles. National Chemistry Week Cleveland Section 13

14 Opening Session Put your goggles on and instruct the students to do the same. Tell the students that they will need to wear the goggles throughout the program while they are conducting and observing experiments, as they would in a laboratory! National Chemistry Week Cleveland Section 14

15 Experiment 1 Experiment 1: Which is the Older Metal: Aluminum vs. Stainless Steel Experiment Summary Participants will test to see which of the metal samples is aluminum and which is the stainless steel by testing for the displacement of copper from aqueous solution. This experiment will be done per student, and will take only about 5 min to complete. Introduce the Experiment Tell the students the following: Although we find aluminum all around us today (e.g. airplanes, pop cans, car parts, etc.) prior to 1886 aluminum was used only for special cases because of its high cost. For example, one of its uses was for making fine jewelry. In 1884, a six pound pyramid shaped piece of aluminum was used as the cap on the Washington monument. The discovery of the modern, cheaper process for purifying aluminum was developed just down the road by Charles Martic Hall at Oberlin College (in 1886). 65 years before Hall found a cheaper way to purify aluminum, a Frenchman named Berthier found that adding chromium to iron made a substance that was more resistant to rust than iron itself. This alloy (i.e. mixture of metals) is referred to as stainless steel. The pieces of metal foil on your table are either highly pure aluminum or stainless steel. The samples were mixed up when the special collection of art and artifacts was being moved. The aluminum is from mid-19 th century jewelry and the stainless steel was used to make copies of that jewelry. At the time, the stainless steel copies were less expensive that the more valuable aluminum. Aluminum can react with solutions of copper (which tend to have a nice blue color) to form copper metal, but stainless steel has no such reaction with copper solutions. Perform the Experiment Simultaneously with the Students Do the following: Have the students locate the opaque 3-oz. plastic cup of the blue copper sulfate solution Have each student take one each of the two types of metal pieces. Have the students take turns using a pipet to add 1-2 drops of copper solution to each of their foil pieces. (You may need to show them how the pipet works.) Have them each keep a close eye on each of their samples and pay close attention to any changes they see. National Chemistry Week Cleveland Section 15

16 Conclusions Tell the students the following: Experiment 1 Have students describe what they saw. Was there any difference between the two pieces of foil? What did the samples look like while the reaction was happening? Sometimes we can use a simple chemical reaction to distinguish between different metals that look very similar. The aluminum reacted with the copper solution, whereas the stainless steel did not. Have the students place the Al in the authentic, & the SS in the replica areas of the form. While aluminum is quite common today, it was not always this way. Before a good chemical process was invented, aluminum samples were rare and unique, and therefore attractive to artists making things like jewelry. Additional Information If Needed: Technical Background The addition of approximately 12% chromium to a steel will significantly increase its resistance to corrosion and oxidation. A thin passive oxide layer is formed on the surface of the steel and this offers protection to many corrosive substances. As early as 1821 a Frenchman, Berthier, recognised that iron alloyed with chromium was more resistant to acid attack. (From: On February 23, 1886, in his woodshed laboratory at the family home on East College Street, Charles Martin Hall succeeded in producing aluminum metal by passing an electric current through a solution of aluminum oxide in molten cryolite. Aluminum was a semiprecious metal before Hall's discovery of this economical method to release it from its ore. His invention, which made this light, lustrous, and nonrusting metal readily available, was the basis of the aluminum industry in North America. Before 1886, aluminum was a semi precious metal comparable in price to silver. Although the element had been investigated by many European scientists, the only way to prepare the metal was by the complex and difficult process that culminated in reacting metallic sodium with aluminum chloride. When the Washington Monument was completed in 1884, a 6- pound pyramid of this costly aluminum was placed as an ornament at the very top. It also served as the tip of the lightning rod system, a practical application of the high electrical conductivity and corrosion resistance of this remarkable metal. From: Aluminum is one of the most abundant metals on earth. It can be recycled over and over again. Recycling aluminum takes much less energy than mining the mineral bauxite from the earth to produce new aluminum. National Chemistry Week Cleveland Section 16

17 Experiment 1 Greek mathematician Archimedes may have been the first "fakebuster" when it comes to metals. He tested a king's "gold" crown using density and found that the crown was a fake! It was not dense enough to be pure gold! January/February 2001) National Chemistry Week Cleveland Section 17

18 Experiment 2 Experiment 2: Paint Prussian Blue Experiment Purpose & General Methodology The students will prepare a modern day pigment, Prussian blue, and paint their own picture with it. Students will do a chemical test to distinguish between the Prussian blue pigment they created and an older pigment, ultramarine, which does not react. They will also use this test to distinguish the authentic and replica painting samples. This experiment should take about 10 minutes. Introduce the Experiment Tell the students the following: Two paintings were found in our mixed-up crates of art. Tell the students that they have small samples taken from the excess canvas on the backside of the two paintings. Ask the students how they might determine which sample came from the old painting and which came from the new painting. As the expert, indicate that there are a number of special tests that can be done without destroying the painting but these require expensive equipment which we do not here today. Indicate that there are also destructive methods of determining if the painting is old or new. Ask the students for the predominate color in their painting samples. (Blue) Tell the students that there are a number of blue pigments used today and in the past and that you have narrowed down the blue pigment possibilities to two: Ultramarine or Prussian Blue. Mention that as an art conservation chemist, you were on the Internet just today and learned that Ultramarine is an older pigment that was used in the twelfth century, but Prussian blue is a newer pigment that was not used before the 18 th century. Tell the students that they will make their own Prussian blue paint, and then use a simple test to help distinguish between the authentic (old) and replica (newer) painting samples. Perform Experiment Simultaneously with the Students Do the following: Have one student take the cup with solution A and another take the cup of solution B. Ask the students to describe the colors of these individual solutions. National Chemistry Week Cleveland Section 18

19 Experiment 2 As the demonstrator, take your own solution A and pour it into solution B while everyone watches the instantaneous color change. Tell them it is necessary that the pigment be stirred thoroughly with the craft stick; stir as you count to 30. Next add the powder marked CaCO 3 to the pigment and mix thoroughly again. Now ask the students to do the same: pour solution A into the larger cup containing solution B and stir. Have another student add the powder CaCO 3 and continue stirring. Let the students know that they can now use this pigment to make their own painting using one of the half-sheets of paper and a Q-tip. Give the students a few minutes to make their own masterpiece, while you also do one for the identification technique. Collect all the pigment and Q-tips and have the students place their paintings out of the way before you proceed. You will now show them a test on your Prussian blue painting to distinguish the newer Prussian blue pigment from the older Ultramarine pigment. Fill the pipet with the NaOH solution. At each table, show the effect that one drop of this solution has on the Prussian blue pigment of your recently completed painting. (It will change the pigment color.) Now test for the new and old paintings on the samples at the students tables. Put a drop or two of the NaOH solution on each of the samples at the student tables. Conclusions Tell the students the following: With this simple test we were able to distinguish between the two pigments which one is old and which is new. Have the students observe the effect of the NaOH on the pigment, then separate their painting samples as authentic /old (no change) or the replica /new (color change). Both of these pigments are used today, but the ultramarine is often synthetically produced to make it a little less expensive. Because we knew we had one old and one new painting, and that ultramarine was used 500 years before the Prussian Blue was created, we had our answer. Thank them for helping to solve this problem with you. National Chemistry Week Cleveland Section 19

20 Additional Information If Needed: Technical Background Experiment 2 All paints have two basic components-- a pigment (coloring material) and a medium (liquid to spread the pigment). To make a permanent paint, the liquid medium must have two parts, a solvent that evaporates and the film former that hardens, leaving a layer that protects the pigment and sticks to the object being painted. Prussian blue paint is created by mixing hydrates of iron (III) chloride (a yellowish solution) with potassium ferrocyanide (a nearly colorless solution) to form a highly colored very stable complex blue ion: FeCl 3 + K 4 Fe(CN) > KFe(II)Fe(III)(CN) KCl This results in a mixed valence compound which undergoes charge transfer. The energy associated with the readily shifting electron between the two iron ions is about the same as the energy of light in the red, orange, and yellow parts of the spectrum ( nm wavelengths). As a result, Prussian blue absorbs these colors and reflects the bluish part of the spectrum. Prussian Blue was discovered in the early 18th century. Ultramarine blue was originally created by grinding lapis lazuli, a semi precious stone. It began to be used as a pigment in the 12th century. It has always been one of the costliest and most precious of painting materials. Today it is made artificially. Ultramarine will not change color when exposed to NaOH, but Prussian Blue will rapidly fade to a much lighter, pale yellow color. National Chemistry Week Cleveland Section 20

21 Experiment 3 Experiment 3: Papers and Inks Chromatography and Fluorescence Experiment Purpose & General Methodology. The students will compare "new" and "old" samples of paper using UV fluorescence to determine which "sketch" is the authentic version and which is a modern reproduction. The students will use chromatography to conduct a second test on samples of the ink from the authentic and replica pieces of artwork. This experiment has two parts. Each student will have two paper samples to test. Each table will share one experimental set-up for the chromatography. Total time is 10 minutes. Introduce the Experiment Tell the students the following: Show the students the two sketches and pass them around. Tell them that one is known to be an older sketch, whereas the other is a modern-day reproduction. Ask the students if they know of any way to tell which of the two sketches is old, and which is new. Tell the students that art conservationists can do tests on papers and on inks to determine if the sketches were made using materials or techniques that were not available until modern times. The test that you will be using on the ink samples is called chromatography. Chromatography takes advantage of the fact that different dyes stick to paper differently. Our experiment will use water as the carrier to distinguish between ink that is water-based and ink that is not water-based. The test that you will be doing on the papers uses an ultraviolet light to look for differences in the papers. Perform the Experiment as a Demonstration, then Simultaneously with the Students Do the following: Pick up the chromatography samples and carefully place both strips into the cup containing a small amount of water such that the black ink marks are near, but not under the waterline. Fold any excess paper over the lip of the cup. Instruct the students to do the same. Ask the students if they see anything happening. (They should see the water starting to soak up the paper.) National Chemistry Week Cleveland Section 21

22 Experiment 3 Tell the students that we need the water to soak most of the way up the paper, which will take a little bit of time, so we will come back to this part of the experiment after we look at the paper samples. Hold up the sketch samples and ask the students to locate their paper samples. Have the students each take one sample form each pile of paper. Tell the students that you will be using an ultraviolet light to look for differences in the paper samples. Ask for a volunteer (student or adult observer) to operate the lights. Turn on the black light and have the volunteer turn off the room lights. Hold the black light above each sketch to see if it fluoresces (glows) or not. Identify the sketch on the paper that fluoresces as the "replica" and the sketch on the paper that does not fluoresce as the "authentic" artwork. Turn the room lights back on and have the students bring up their paper samples to see if they fluoresce of not. Test the demonstrator s paper samples as well. (Turning off the room lights again as necessary.) Turn the room lights back on and have the students return to their tables and classify their paper samples as authentic or replica. Return to the chromatography experiment and remove both samples from the water. Blot some of the excess water gently on the paper towel. Ask the students what difference they see between the two samples. (One ink sample has moved and separated into colors; the other ink sample has not moved.) Have the students classify their chromatography samples as authentic (ink has moved up the paper) or replica (ink did not move). Conclusions Tell the students the following: Newer papers are often contain optical whiteners to make them look brighter, whereas older papers do not (optical whiteners were not generally used until after WWII.) Optical whiteners have the property of fluorescence, which means they appear to glow brightly under an ultraviolet light (sometimes called a black light ). Optical whiteners are also added to laundry additives to make clothes appear whiter and brighter. The ink sample that climbed up the chromatography sample is a water-based ink. Waterbased inks will run when the paper gets wet (like washable markers and some writing pens). Water-based inks have been around for a very long time and would be indicative of the type of ink in our authentic sketch. The ink sample that did not move was made using a non-water based ink. Non-water based inks use special solvents and have not been National Chemistry Week Cleveland Section 22

23 Experiment 3 available for as long as water-based inks. The non-water based ink is indicative of our replica sketch. Black ink is made of many different colored dyes. When they are all mixed, they appear black. In our chromatography experiment, we caused the different dyes in the water-based ink to be separated so that the original colors could be seen. As the water soaked into the dry paper, it carried the water-based dyes along with it, but to different degrees. The dyes that stick to the paper better move less; the ones that dissolve in the water better move more, causing them to separate from one another. Additional Information If Needed: Technical Background 4,000 B.C - Ancient Egyptians invented papyrus, the first substance similar to paper. Papyrus was a woven mat of reeds, pounded together into a hard, thin sheet. The word "paper" actually comes from the word "papyrus". Later on in history, the Ancient Greeks used a kind of parchment made from animal skins for the same purpose. A.D Paper as we know it was invented by Ts'ai Lun, a Chinese court official. It is believed that Ts'ai mixed mulberry bark, hemp, and rags with water, mashed it into a pulp, pressed out the liquid and hung the thin mat to dry in the sun. Paper would set off one of mankind's greatest communication revolutions. Literature and the arts flourished in China. Chromatography is an analytical technique that can be used to determine the presence of small amounts of samples. It is often used in forensic chemistry and in authenticating inks on old documents. Fluorescence is a form of luminescence. Luminescence involves the emission of light by means other than combustion, and thus occurs at lower temperatures than combustion. Luminescence involves absorbing energy at certain wavelengths and then emitting this energy as light. This is accomplished by electrons getting excited and jumping from inner orbitals of the atoms to outer orbitals. When the electrons fall back to their original state, a photon of light is emitted. If the light lasts for a short time, it is called fluorescence; if it lasts a long time, it is called phosphorescence. The wavelength of light emitted has less energy (longer wavelength) than the one absorbed. Ultraviolet light can also be used to find repairs that have been made to a painting. The new United States paper currency is currently being made with fluorescent strips to help authenticate it and make it difficult to produce forgeries. The new $5, $10, and $20 bills (and probably larger bills as well) have strips that glow with different colors under UV light. National Chemistry Week Cleveland Section 23

24 Experiment 4 Experiment 4: Are You Being Framed? The Answer is Clear! (AKA: Glass vs. Polycarbonate) Experiment Purpose & General Methodology The students will determine if the glass that was covering a painting is real glass or a new synthetic polymer. Each table will share a set of glass and plastic slides, but each student will participate in the experiment. This experiment will take 3 minutes to complete. Introduce the Experiment Tell the students the following: Ask: Has anyone been to the Cleveland Art Museum? Do you remember seeing paintings? At the Art Museum did you notice which paintings have glass over them and which don t? There is a chemical reason that some do and some don t! Oil paintings are not covered with glass. They usually have a frame but no glass. This is because oil paintings often take a year to dry. Volatile gases (fumes) come off the painting during this time. After one year, when the paint is hard and dry, the painting is varnished to protect it. If you paint a picture and give it to someone, make sure they give it back in a year, so you can varnish it! Watercolors and pastels and modern acrylics are usually framed and put under glass to protect them. However, if the acrylics look like oil paint (if the paint is laid on thickly and the strokes are visible) they look good without glass. If a painting came to the Art Museum, the art conservationists could do some tests to see if it were really old or a recently painted fake. They could even test the glass covering the picture to gain more information. Glass has been around for a LONG time. It was first made around 5000 B.C. Today it is still the best material to cover paintings except in some cases. Glass is cheap, readily available (can buy it at a lot of stores), very clear or transparent (can see through it without distortion), won t scratch easily, and won t buckle. A disadvantage is that it can break and shatter. (Today, there are about nine kinds of glass with special features sold in framing stores.) In today s world, chemists have developed plastics that can take the place of glass. Even the windshields of modern airplanes can be made of plastic instead of glass. There sometimes is an advantage to using plastic instead of glass in the art world to protect paintings: plastic is National Chemistry Week Cleveland Section 24

25 Experiment 4 lighter weight than glass, so when framing a huge picture, framers may suggest plastic. When paintings are being shipped, you may use plastic, for safety reasons, because plastic won t break easily like glass. You can also drill through plastic, and for example, bolt a painting to the side of a boat. The disadvantages of plastic are: it s expensive, it can often be scratched easily, and it can yellow with time. Does anybody here wear glasses? Are they made of glass? Or a modern plastic? How can you tell? We have 2 samples here. One is glass and one is plastic (specifically, polycarbonate). Chemists have various ways to determine which is which. One easy way is to see just how clear the material is. Regular glass will let light through even ultraviolet light or UV (which is more energetic rays of energy than visible light). You probably heard of ultraviolet rays from the sun causing sunburn. But some modern plastics like polycarbonate don t let UV light through. We ll use this property to tell which sample is glass that covered an old painting or a modern plastic that blocks UV light. (We can also test your eyeglasses. Maybe they are made of polycarbonate!) Perform the Experiment Simultaneously with the Students Do the following: Have the students take a sample of the paper which they determined to be new (with optical brighteners), and place it in the middle of their table. Tell one student from each table to pick up the 2 samples and place them on the new paper from the previous experiment. Have the children guess if the samples are glass or plastic. Tell them you will be coming around with a UV light. Turn out the room lights and shine the UV light on each sample and observe what happens. Have the students put the glass sample on the Authentic side of the summary sheet, and the polycarbonate on the Replica side. Conclusions Tell the students the following: The glass sample will allow UV light to pass through it and the UV rays will cause the optical brighteners in the paper to fluoresce. You can see the bright white color through the glass. National Chemistry Week Cleveland Section 25

26 Experiment 4 The polycarbonate sample with its UV filter, a modern material, absorbs the UV light and the paper appears dark under it. National Chemistry Week Cleveland Section 26

27 Additional Information If Needed: Technical Background Artists Use of Glass and Plastic Experiment 4 Regular glass is most commonly used in framing. Advantages: cheap, readily available, longlasting, very transparent, fairly scratch resistant, won t buckle, no distortion of the painting, unaffected by the normal, everyday environment, easily cleaned. Nowadays, properties can be adjusted so that glass blocks UV (because UV light can fade a painting over time), is nonglare (although it tends to fuzz the painting if separated from it by more than one mat), etc. Disadvantages of glass include weight (for a huge painting, glass may be too heavy); it can break and shatter (which is a safety concern); it has a slight green tint which may not be ideal for fine watercolors or drawings. Disadvantages of plastic: it scratches more easily than glass, the quality of its appearance is not as good as glass, it s more expensive than glass. GLASS Glass is one of the most ancient materials used by people. It was a mixture of silica sand (from beaches), soda ash (from burned wood), and limestone (from seashells). This stuff is still readily available, and amazingly, modern soda lime silicate glass is similar to the old glass! Silica is units of silicon and oxygen joined together. In sand, these units are in an orderly, crystalline pattern. To make glass, the sand and additives are put in a furnace and melted and fused together. In glass, the silica units are disordered and jumbled; glass is an amorphous substance (meaning no distinct crystalline structure). What are 2 ways that glass is made in nature?! One is by volcanoes. This glass is called obsidian (geologic glass). It was used by people thousands of years ago for arrows, jewelry, etc. The other way is when lightning hits sand. You can see these glass tube-like structures in the museum at the sand dunes at Kitty Hawks, Outer Banks, NC. POLYMERS/PLASTICS The polymer used in this experiment is polycarbonate. It is used to store food and beverages, in bike helmets, in CDs, in eyeglasses. It is very durable and shatter-resistant. The world s first synthetic polymer was Bakelite in The man who invented it was Leo Baekeland, who became an ACS president. He combined two small molecules into long, 3-D chains to make a strong, hard material. Nylon was made in It was used in WW11 for parachutes, ropes, etc. The plastic that won the war, however, was polyethylene, used as insulation in radar. Methyl methacrylate is the clear, hard plastic in Lucite and Plexiglas, used in making glasses, camera lenses, windows in airplanes, etc. Modern chemistry has continued work in developing useful polymers. National Chemistry Week Cleveland Section 27

28 Experiment 5 Experiment 5: Fabric Identification with Powdered Drink Mixes as Dyes Experiment Purpose & General Methodology Each student will dye a fabric swatch to test between natural and synthetic fabric fibers. The experiment should take about 10 minutes to complete. Introduce the Experiment Tell the students the following: Tell the students that there are dyes that are only taken up by certain types of fabrics, and that we will test for synthetic (man-made) vs. natural fibers with a dye test. Perform the Experiment Simultaneously with the Students Do the following: Explain to the students that a chemist wanting to test a new dye on different fabrics would use a multi-fiber ribbon such as the one you are using. Immerse your multi-fiber strips (one in each different dye) in the dye. Let them remain in the dye for 3-4 minutes. Ask the students if they can name different natural fabrics (cotton, silk) or synthetic fabrics (nylon, polyester, rayon). Discuss the different types of fibers in the test ribbon. Remove the strips from the dyes using a plastic fork and lay out on paper toweling to dry. Now test the fabric pieces that were found in the special art collection. Tell the students to each take one of the fabric pieces found on your table and immerse it in the cup of dye. Let it remain in the dye for 3-4 minutes. Remove the fabric from the dye using the plastic fork, and lay it out on a piece of paper toweling to dry. Conclusions Tell the students the following: Identify the fibers in your sample. Ask them whichof the samples have turned color. Ask the students to name a natural fiber, a synthetic fiber. Ask the students if their sample was a natural fiber or a synthetic fiber. National Chemistry Week Cleveland Section 28

29 Experiment 5 Assuming that an older painting or fabric artifact, such as a tapestry, would be made of a natural fiber and that food dyes were used prior to the twentieth century for dying fabrics it is expected that the natural fiber will be dyed by the drink mix and the synthetic fiber will not be dyed. Have the students classify their fabric samples as authentic (natural fiber) or replica (synthetic fiber). Additional Information / Technical Background Since Prehistoric times people have dyed cloth. The wearing of the purple has long been synonymous with royalty, due to the cost and rarity of Tyrian purple, a dye derived from the sea snail Murex brandaris. The organic chemical industry originated with William Henry Perkin s discovery of the first synthetic dye, Perkin s Mauve, in Acetate and viscose are derivatives of cellulose but direst dyeing of these fibers is more difficult than direct dyeing of cotton, also a form of cellulose. A simple hypothesis on dyeing is that the intensity of a dye on a fiber will depend on the number of strongly polar or ionic groups in the fiber molecule. The more polar groups present, the easier it is to dye the fiber. Nylon is a polyamide and made by polymerizing adipic acid and hexamethylenediamine. The nylon polymer chain can be prepared with on acid and one amine group at the termini, or with two acids or two amines at the terminals. Except for these terminal groups, there are no polar centers in nylon, and consequently it is difficult to dye. Similarly, Dacron, a polyester made by polymerizing ethylene glycol and terephthalic acid, has few polar centers and consequently is difficult to dye. Even more difficult to dye is Orlon, a polymer of acrylonitrile. Wool and silk are polypeptides crosslinked with disulfide bridges. In wool and silk, the acidic and basic amino acids provide many polar groups to which a dye can bind, thus making these fabrics easy to dye. Identity of multi-fibers (starting from black thread down) Acetate, Self Extinguishing Fiber, Arnel (bright) Bleached Cotton, Creslan 61, Dacron 54, Dacron 64, Nylon 6,6, Orlon 75, Spun silk, Polypropylene, Viscose (Rayon), Wool National Chemistry Week Cleveland Section 29