Silver Saver – Science Nation

MILES O’BRIEN: Nothing shines like polished silver.
But keeping the tarnish at bay is never ending work, and polishing isn’t just a pain. It also rubs away
some of the precious metal, whether it’s your grandmothers silver bowl or an
18th Century museum treasure. TERRY DRAYMAN-WEISSER: So we’re always
looking for some kind of barrier that will protect the surface so that
you don’t have to keep polishing. MILES O’BRIEN: At the Walters Art Museum
in Baltimore, the barrier of choice is lacquer brushed on by hand.
Often it affects the color. RAY PHANEUF: The art conservators have an
expert eye and they say, “oh, it has a bluish cast”. All right. MILES O’BRIEN: With support from the National
Science Foundation, Material Scientist Ray Phaneuf and his team are working with the museum producing
a protective coating so thin you can’t see it with the naked eye. Using a special reactor
inside a clean room, they produce nanometer thick films of aluminum oxide. The films conform
to the recesses and protrusions of the silver, creating a protective barrier. RAY PHANEUF: The method that we use to a
–to apply it is called atomic layer deposition. So literally we’re able to control the thickness of
the film at a–at a subnanometer level. An atom is one one-hundred thousandth of the
thickness of a human hair. MILES O’BRIEN: Conservators say atomic layer
deposition, or ALD, will have to pass rigorous testing before they use it to protect these
irreplaceable treasures. MALE: That’s the actual active element
of any spectrometer. MILES O’BRIEN: In the lab, they measure how
light reflects off the surface of a test wafer and how the ALD coating affects its color.
Another test measures how quickly sulfur penetrates the coated wafer. Sulfur is what tarnishes silver.
This helped scientist’s figure out how long a barrier will last. RAY PHANEUF: If we can increase the–
the lifetime of these films to a century, we may not need to do this very often. MILES O’BRIEN: Conservators wont give ALD
a thumbs up until they can show it works better than the lacquers they’re using now,
which have to be reapplied every decade or two. TERRY DRAYMAN-WEISSER: And also we’re
concerned about how it is removed. Right now with the lacquer,
you can remove it with solvents. MILES O’BRIEN: If ALD proves a shining success,
works like these will remain at their best for future generations to enjoy. For Science Nation I’m Miles O’Brien.

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