## Seventh Grade Students Travel to Winterthur to Learn about the Science of Museum Collecting.

In many science textbooks, the story of Archimedes and his use of density to detect the purity of gold in King Hieros of Syracuse's crown is used as a way to illustrate the practical use of characteristic properties of matter. In the story Archimedes is tasked with the problem of figuring out the purity of gold in the crown, but because it is a crown, he cannot destroy or change the shape of it. Archimedes uses density, the amount of mass per given amount of volume, as his starting point. Finding the mass is easy, he needs to place the crown on a scale. Finding the volume is more difficult. The crown cannot be destroyed. It would be easy enough to melt the crown into a block and calculate the volume, length x width x height, but this is not an option. Archimedes gets tired of thinking and decides to take a bath. As he steps into the tub, he notices the water level rises and he shouts out "Eureka!". Archimedes knows he can use water displacement to find the volume of the crown and can now find the density of the crown and compare it to the density of pure gold.

A gold coin from the Winterthur Collection

Students in the seventh grade at Brandywine Springs use the details of this story as part of their Properties of Matter curriculum. Students are put to the task of identifying materials based on their chemical properties. Students use a variety of techniques to do this in a lab, but by visiting Winterthur Museum and Gardens they gain an insight into the practical application of identification. Just like Archimede's problem where he cannot melt down the crown, Art Conservationists must use their knowledge of Art History and Chemistry to learn more about the materials that are part of our cultural heritage and help preserve them for future generations to enjoy.

If Archimedes had access to today's modern tools, he might consider some of the specialized equipment that conservationist use to help identify the materials that make a piece of artwork. One piece of equipment that students got to visit on their field trip was the XRF. XRF is an acronym for X-ray fluorescence. XRF analyzers determine the chemistry of a sample by measuring the fluorescent (or secondary) X-ray emitted from a sample when it is excited by a primary X-ray source. By analyzing the readout on the XRF conservationist can determine how much of each element is in the piece. This information can be compared to art history records to determine if the piece was created by a certain artist, at a certain range of time, or from a certain location depending on the material. Another chemical analyses technique that requires specialized equipment at Winterthur is HPLC. HPLC stands for high pressure liquid chromatography. Incredibly small samples can be put into a machine that separates the parts of the mixtures that make up a small paint sample from a piece. Chromatography was originally developed to identify plants based on their chlorophyll. Liquid and Gas chromatography today is used in art conservation, forensic science and in the oil and gas industries to identify materials.

Scientific measurements that help identify materials is not the only science that goes on a museum. On the field trip, students learned about the measurements museum conservationists must continually measure to insure that the materials that are on display stay the same and continue to be enjoyed by future visitors. Preservation is an important part of the job of art conservation. Measurements of light (lux), humidity, and temperature must be accounted for. When on display, different materials like wood, paper, metal, ceramics, paintings, and textiles each have different tolerances of light, temperature and humidity.

Students also take into consideration the insect pests that could cause serious damage to the textile collection that Winterthur displays and stores. A constant vigilance and routine cleaning of pieces insure that termites, Museum beetles and carpet beetles don't consume the display pieces. Protein based material like the ones found in wood, wool, cotton, and silk are the food and habitat for these insects no matter if it is the woods or at the museum.

The trip to Winterthur gives students an idea of what science is used by the staff of a museum. A variety of scientific fields like chemistry, entomology, and optics have to be mastered in addition to art history and hand skills to make a master art conservationist. Hopefully students who went on this field trip gained an appreciation of the training and perseverance that this job field requires and have a better understanding of the applications of science employed.

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