Fossil amber shatters theories of glass as a liquid

May 7, 2013 by Karin Slyker
Fossil amber shatters theories of glass as a liquid
20-million-year-old Dominican fossil amber

( —Fact or fiction? Stained glass found in medieval cathedrals becomes thicker at the bottom because glass moves over time. For years researchers have had their doubts, now a team at Texas Tech University has further evidence that the glass is not going anywhere.

" is related to the performance of materials, whether it is inorganic or ," said Gregory McKenna, professor of chemical engineering at Texas Tech. "For example, this would be important to people who own a boat made of fiberglass, or fly in an airplane made with epoxy-based composites. Information like that can help predict if that jet will still be flying in 30 years."

The idea for this research came from a doctoral student's qualifying exam, McKenna said. He gave Jing Zhao a problem relating to diverging time-scales using polyvinyl acetate, a substance often found in adhesives. Her results were consistent with a lack of divergence – contrary to received thought. So they decided to up the ante by performing similar experiments on a much older, ultra-stable glass.

They chose 20-million-year-old Dominican amber, and together with Whitacre Department Chair and Horn Professor Sindee Simon, Zhao performed calorimetric and stress relaxation experiments on the samples.

"What we found is that the amber relaxation times did not diverge," McKenna said. "This result challenges all the classic theories of glass transition behavior."

This research is supported by the National Science Foundation under a grant from the Division of , Polymers Program. The process and results were recently published in Nature Communications.

Meanwhile, McKenna has recently acquired additional samples from around the world, including 220-million-year-old Triassic from Eugenio Ragazzi, a pharmacology professor at the University of Padova in Italy. The team now has plans to perform similar experiments on the new samples.

"We are in the very early stages," McKenna said. "However, our research definitely is 'to be continued.'"

Explore further: In probing mysteries of glass, researchers find a key to toughness

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3.1 / 5 (8) May 07, 2013
30 years ago I stored a 25 ml bulb pipette in a safe location where it would not be broken. It was stored 45' from horizontal by two points that were separated by the full length of the pipette and was submerged in water.

10 years later when it was inspected It's center had drooped under it's own weight by (from memory) 2 to 5 degrees.

2.3 / 5 (8) May 07, 2013
I don't understand how they can equate amber with glass. It's not like glass at all other than being hard to the touch.
May 07, 2013
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3.7 / 5 (6) May 07, 2013
The "glass thicker at the bottom of the frame" notion of amorphous glass is a hugely publicised conjecture that has been going on for well over a century. It stems from a profound misunderstanding about how glass was made in the past. Glassblowers created a large disk of glass that was thicker at the center than the edges. Small panes were then cut out of it. The thicker ends were put at the bottom of the frames or leading.


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