The Art of Science: Returned to Glory
When American artist Augustus Saint-Gaudens finished the Shaw Memorial in 1897, he could not have imagined that his masterpiece would become the subject of a major commemoration 100 years later. The Shaw Memorial, America's first monument to African-American soldiers, became an important part of American art and history. A plaster cast of the memorial, stored outdoors for decades, suffered the effects of weather until restored to life by 20th-century conservators.
Introduction: Metals and Alloys in Our Lives
Activity 1: Alchemy Lab: The Golden Dream
Activity 2: Plaster Activities
frescoes, paints, pigments
alloys, metallic elements, oxidation
INTRODUCTION: METALS AND ALLOYS IN OUR LIVES
Metallic elements silver (Ag), gold (Au) and copper (Cu) are lustrous, malleable, ductile and conductive. For millennia, each has been used to make sculptures, jewelry and structures large and small.
Artists often work with alloys like bronze, steel or brass because of their durability and color. Bronze is a mixture of copper and tin; brass, made in the activity below, is a mixture of zinc and copper. Steel is made of iron and carbon. Alloys are used to make coins, jewelry, sculptures and other items.
When exposed, metals can become damaged. Why did the Statue of Liberty, a copper structure, turn blue-green? After many years of exposure to humidity and the sulfur compounds in acid rain, copper in the statue oxidized to form copper compounds that are blue-green in color. You may also see this on copper roofs and pennies. This same process of oxidation similarly affects silver. Sulfur-containing compounds in found food or the atmosphere cause silver to oxidize and tarnish.
The original Shaw Memorial was made of bronze. Saint-Gaudens later made a plaster cast of the sculpture. As you see on Frontiers, 20th-century scientists restored the plaster to Saint-Gaudens's bright and shining vision.
ACTIVITY 1: ALCHEMY LAB: THE GOLDEN DREAM
Alchemists in the Middle Ages believed they could turn ordinary metals into gold. In this lab, you become a 20th-century alchemist and turn pennies into shiny "silver" and "gold".
Note: We suggest that this lab be performed as a teacher demo or as a supervised chemistry experiment in the lab.
Show students how an alloy is made.
Note: NaOH should be handled with great care. It is corrosive and can burn skin. Zinc dust should not be inhaled. Safety goggles should be worn the entire time. This lab should be performed under a hood.
- 20 mL of 6 M NaOH
- 0.1 g zinc dust
- evaporating dish
- hot plate
- 200 mL beaker of water
- Bunsen burner
- Place zinc dust in evaporating dish.
- Add 20 mL of NaOH solution to the dish, on top of the zinc.
- Set hot plate to medium heat and place the evaporating dish on top.
- Heat for 5 minutes. Do not boil. When dish is hot, place a penny in it. Heat for two minutes or until the penny is coated and becomes silver in appearance.
- Remove the penny from the dish with tongs and drop into water. When cool, wipe the penny clean with a cloth to remove excess zinc.
- Using tongs, hold the penny in the flame of a Bunsen burner and gently heat. The penny should turn "gold" (brass). (Do not overheat the penny.)
- Dip the penny in the beaker of water and cool to touch.
In Step 4, the penny was coated with zinc atoms. In Step 6, when the penny was heated, the copper atoms of the penny and the zinc atoms coating the penny mixed and turned gold in color, but actually formed the alloy brass.
DISPOSAL OF CHEMICALS:
Pour off NaOH into a 250 mL beaker of water to dilute and pour the mixture down the sink. Wipe zinc residue and evaporating dish with a paper towel and dispose.
ACTIVITY 2: PLASTER ACTIVITIES
You may have made a plaster face mask in art class or mixed plaster of Paris for home repair projects. Plaster of Paris is actually calcium sulfate (CaSO4 and 2H2O), more commonly called gypsum. It can be found in all parts of the world, but was named plaster of Paris because of its original use by the French building industry.
In making plaster of Paris, calcium sulfate is heated to the point where it loses most of its water, then ground into a powder or a calcined state. The plaster powder is remoistened and made into a liquid paste that hardens quickly. Before it becomes firm, it can be molded into casts, sculptures, ceramics, dental and surgical products, stucco walls, etc.
USING PLASTER OF PARIS, TRY THESE PROJECTS:
- Make a fresco! Mix plaster following directions on the package. Pour it into a pie pan or other container. Try painting on damp plaster to make a fresco, in the style of Renaissance artists (or 20th-century artists like Diego Rivera). In authentic frescoes, painters use colors made of dry pigments mixed only with water. They mix and paint one small section of plaster at a time. As the lime in the plaster dries and the water evaporates, the color bonds with the plaster, forming a hard surface. Try mixing various paints and pigments and apply to wet and dry plaster.
- Create a 3D sculpture. Pour the wet plaster into an empty milk carton and let it dry. Using tools borrowed from the art department, try your hand at carving.
- Try a restoration project. Conservators who restored the Shaw Memorial found 25 layers of paint, gilt, wax and varnish in some portions of the plaster sculpture. Try exposing your plaster art to the weather or covering it with several layers of paint. Then try to clean or restore it using soap, detergent or other household solvents, and you'll have an idea of what conservators had to deal with.
- Look for other sculptures by Augustus Saint-Gaudens in many U.S. cities. You'll find a list and photos at the National Historic Site.
- The Shaw Memorial is famous for being the first memorial to celebrate the heroism of African-American soldiers. It has been the subject of poetry by James Russell Lowell, John Berryman, Robert Lowell and Paul Laurence Dunbar, and part of a composition by American composer Charles Ives (Three Places in New England). The movie Glory tells the story of the Massachusetts 54th Regiment in the Civil War.
Scientific American Frontiers
Fall 1990 to Spring 2000
Sponsored by GTE Corporation,
now a part of Verizon Communications Inc.