The case of the sticky painting: a fine-arts conservator uses detective work to remove gum from a museum painting.

A blob of paint here and a burst of color there, abstract art may be difficult for some people to appreciate. Last year, a 12-year-old visitor to the Detroit Institute of Arts (DIA) left his mark by sticking a wad of gum on one of the museum's most important abstract paintings.

The Bay, by Helen Frankenthaler, is estimated to be worth $1.5 million dollars. Seconds after the act of vandalism, the museum's security officers sprang into action. They roped off the gallery where the painting hung, and gathered the touring school group--of which the offender was a part--for questioning.

Could the sticky gum be removed without further damaging the artwork?

ART 9-1-1

Alfred Ackerman, the DIA's head of paintings conservation, rushed to the scene. He had rid paintings of spitballs and fingerprints left by inconsiderate visitors before. But he had never removed gum.

One look at the wet gunk adhering to the lower-left corner of The Bay, and Ackerman knew that he had to remove it ASAP. In addition to the gum, "the chewer's saliva and all of the components within the gum--such as sweeteners and flavorings--were pressing in a concentrated area on the painting's surface," he says. Whenever moisture meets a painting, a disaster can happen: The wet substances can act as a solvent that could affect the paint (see Nuts & Bolts, p. 14).

Ackerman placed a magnifying loop over his eyes and took out a pair of superfine tweezers. "It's the type [of tweezers] that jewelers use to set gemstones," he says. With a steady hand, he gently plucked the gum from the painting. But his work wasn't complete. A dark, wet stamp-size residue remained on the painting's surface. "The sugars and other components [of the gum] had saturated the surface and made that area look darker," says Ackerman.

To remove some of this residue, Ackerman used a swab to dab up as much of the sugary moisture as possible. Despite the careful mopping, the gummy spot still remained dark and damp. Ackerman could not tell if the painting would be permanently stained; he had to wait until the splotch dried.

DETECTIVE WORK

On the following day, The Bay was moved to the paintings conservation lab. "It pretty much looked the way it did by the end of the first day," he says. To learn how much gum residue remained on the painting--and how to remove it--Ackerman had to do some detective work.

When the security officers caught the offender, they asked questions to learn what brand of gum the student had been chewing. Ackerman purchased a few packs of the gum and began chomping. "I needed to get a sense of how long it had been chewed before it landed on the painting," he says. By studying the gum wads' texture and coloring, Ackerman determined that the student had attacked the painting with a freshly chewed piece. The fresher a piece of gum is, the more sugars and flavorings it contains. Now Ackerman knew he still had a lot of gummy leftover to remove. But to do so would be challenging due to the nature of the painting.

The Bay, created in 1965, is unlike most paintings before its time: It lacks a protective topcoat of varnish and a traditional ground layer, or primer. This undercoating of paint covers bumps and holes on a canvas, creating a smoother and less porous surface on which an artwork rests. Frankenthaler's work rests directly on the raw canvas. The artist also used a water-based acrylic paint, a relatively new product at the time.

Unlike traditional off paint, which is commonly thinned with a solvent called turpentine, acrylic paint thins with water. Paint is a colloid. This mixture contains fine particles of undissolved color pigments held together by a binding material--in this case an acrylic resin. As an artist thins the paint, the pigments spread out. Frankenthaler used very watered-down paint. The thin paint soaked through the canvas fibers, staining it like a piece of dyed cloth. "If I were to rub [the gum stain] hard with a cotton swab and water, I could easily remove some of the pigments," says Ackerman. That would destroy the painting.

DELICATE CASE

Ackerman wondered: What's the safest way to clean art that is similar in material to delicately dyed fabric? He decided to use a method similar to dry cleaning.

Dry cleaners do not use water as a solvent to dissolve dirt on clothes because the liquid takes too long to evaporate, or turn into water vapor. If water interacts with a piece of delicate fabric for too long, it can cause not only dirt, but sensitive dyes to leach out as well. Dry cleaners use fast-evaporating chemicals instead. When used correctly, these solvents rid the material of dirt without affecting the dye.

Ackerman chose a very fast-evaporating solvent called Hexane. Peering through a microscope, he was able to observe the gum stain at a magnification of 10 times. Such a close look helped him work with precision: Using cotton swabs with tips no larger than a pinhead, he dabbed the stain cautiously with the solvent, hoping the sugary substances would dissolve into it quickly. "I would work on a little spot and let it dry," he says. "I wanted to make sure that I wasn't going too far. I would check the swab to make sure that I didn't pick up pigment particles." After six days of painstaking dabbing, the stain was finally gone.

Thanks to Ackerman's rapid response and determined detective work, The Bay has now returned--spot-free--to its place in the gallery. And the DIA has been experimenting with different types of vandal-proof barriers to ensure that visitors can enjoy the painting with some distance and respect.

nuts & bolts

A solution is a well-blended mixture containing these two parts: a solvent and a solute. The solvent makes up the larger part of a solution. The solute is the part of a solution that dissolves into the solvent. As solute particles separate from each other, they become surrounded by particles of the solvent.

HANDS-ON sCIENCE (No Lab Required).

After reading "The Case of the Sticky

PREDICT

When the Detroit Institute of Arts needed to remove a sticky gum stain from a masterpiece painting, they had to search for the right solvent for the job. Different solvents dissolve some substances but not others. Which solvent do you think will best dissolve sugar: water, isopropyl alcohol, or vegetable oil?

MATERIALS

safety goggles * measuring spoons * sugar * plastic bag that zips closed * food coloring * marker * 3 clear plastic cups * water * paper towels * isopropyl alcohol * vegetable oil * paper * pencil

NOTE TO TEACHERS: Isopropyl alcohol is a chemical and should be handled carefully. See this issue's Teacher's Edition for additional lab safety Instructions.

DIRECTIONS

1 Put on your safety goggles.

2 Place one tablespoon of sugar and two drops of food coloring into the plastic bag.

3 Seal the bag securely shut, leaving some air in the bag. Shake the bag vigorously until the food coloring has evenly colored all the sugar.

4 Using a marker, write the word "Water" on one cup, "Isopropyl Alcohol" on a second cup, and "Oil" on the last cup.

5 Measure two teaspoons of water and place it into the cup labeled "Water." Dry off the spoon with a paper towel. Now measure two teaspoons of isopropyl alcohol and put it into the cup labeled "Isopropyl Alcohol." Dry off the spoon again, and add two teaspoons of vegetable oil to the cup labeled "Oil."

6 Measure a teaspoon of colored sugar from your plastic bag and put it into the cup labeled "Water."

7 Gently swirl the "Water" cup for 60 seconds. What happened to the sugar? What happened to the food coloring? On a piece of paper, record the name of the cup and what you observe.

8 Repeat Steps 6 and 7 for the "Isopropyl Alcohol" and "Oil" cups.

CONCLUSIONS

1. Which solvent best dissolved the sugar?

2. A mixture is made of two or more substances that are blended together but are not chemically combined. A solution is a very well-blended mixture that has the same properties throughout. Which cup(s) contained a solution? Explain.

Answers

HANDS-ON, p. 15

NOTE TO TEACHERS: Isopropyl alcohol is a chemical and should be handled with care. Before students start the experiment, have them stow away all food and drinks. Also, check to see that every student is wearing goggles. If students accidentally ingest the alcohol or have it come into contact with their eyes, follow the instructions found on this Web site: www.nim.nih.gov/medlineplus/ency/article/002660.htm

1. Water best dissolved the sugar

2. The water-filled cup contained the solution

web extra

To learn more about art conservation, visit: http://aic.stanford.edu/

PRE-READING PROMPTS

Jump-start your lesson with these pre-reading questions:

* Alfred Ackerman, head of paintings conservation at the Detroit Institute of Arts (DIA) says art conservators need to be well-educated in these three areas: studio art, art history, and science. Why do you think that may be?

* Jolly Baptiste Belin is believed to have opened the world's first dry cleaner in Paris in the 1840s. How does dry cleaning work, and how does this process help paintings rest oration?

* To protect their artworks, the DIA, like many other art museums, has very strict rules of conduct for visitors. For example: Visitors can't run in the galleries. Can you think of some other rules that museum visitors might need to follow? (For more information, see: www.dia.org/education/student_tours/index.asp)

CRITICAL THINKING:

* Art museums protect the artworks in their collection with the utmost care because they are highly valuable. Can you think of what makes an artwork valuable--besides its monetary value? (Here are some possible answers: An artwork may be a visual record of a historic period; people admire the artist's creation; the work helps document the social climate during the artist's time.)

CROSS-CURRICULAR CONNECTIONS:

ART HISTORY: Have each student select a different period or style of art. Then have him or her do research to create an informational poster about the selection. Display the posters on the bulletin board to create all art history discovery gallery.

RESOURCES

* Visit this Web site from the Detroit Institute of Arts to read more about how Alfred Ackerman restored The Bay: www.dia.org/PressReleases/showpressreleases.asp?ID=288

* To watch online videos about science and technology in art conservation, visit this Web site from the Art Institute of Chicago: www.artic.edu/aic/students/sciarttech/2e.html

* This University of Delaware Library Web site is filled with Internet resources about art conservation: www2.lib.udel.edu/subj/artc/internet.htm

* To see a diagram on the anatomy of a painting, visit this Web site from the Minneapolis Institute of Arts: www.artsmia.org/restoration-online/guercino/anatomy-painting.cfm

The Case of the Sticky Painting

DIRECTIONS: Answer the following in complete sentences.

1. Why did Alfred Ackerman need to immediately remove the wad of chewing gun from The Bay?

2. Why did Ackerman chew gum as part of his investigation?

3. What kind of mixture is paint? What is paint made of?

4. Why don't dry cleaners use water to dissolve dirt on clothes?

5. What is a solvent and what is a solute?

ANSWERS

1. Ackerman had to immediately remove the gum because in addition to the gum, the chewer's saliva and all of the components within the gum--such as sweeteners and flavorings--were pressing in a concentrated area on the painting's surface. The wet substances can act as a solvent that could affect the paint.

2. Ackerman needed to get a sense of how long the student chewed the gum for before it landed on the painting. By chewing gum and studying the wads' texture and coloring, Ackerman determined that the student had attacked the painting with a freshly chewed piece. The fresher a piece of gum is, the more sugars and flavorings it contains and the more gum residue Ackerman needed to remove

3. Paint is a colloid This mixture contains fine particles of undissolved color pigments held together by a binding material. As an artist thins the paint, the pigments spread out

4. Dry cleaners don't use water to dissolve dirt on clothes because the liquid takes too long to evaporate. If water interacts with a piece of delicate fabric for too long, it can cause not only dirt, but sensitive dyes to leach out as well.

5. A solvent and a solute are the two parts of a solution. The solvent makes up the larger part of a solution. The solute is the pad of a solution that dissolves into the solvent.