Finding Fake Art
IF PAUL REVERE HAD MADE EVERY SILVER SPOON OR CUP ATTRIBUTED TO
HIM, HE WOULD NEVER HAVE HAD TIME FOR HIS FAMOUS RIDE.  THIS
AMERICAN HERO--WHEN HE WASN'T OUT WORRYING ABOUT ONE LAMP BY
LAND OR TWO IF BY SEA--WAS A SILVERSMITH.  AND MANY OF HIS PIECES
HAVE BEEN HANDED DOWN THROUGH THE AGES, BUT SO HAVE MANY
FORGERIES.  THIS IS THE KIND OF THING THE CURATORS AT THE WINTERTHUR
MUSEUM IN DELAWARE HAVE TO BE AWARE OF.  THE MUSEUM SPECIALIZES IN
COLONIAL ART AND OBJECTS AND IT USES STATE OF THE ART SCIENCE
TECHNIQUES TO SEARCH OUT THE FAKES SAYS CHEMIST JANICE CARLSON. 
ONE OF HER PRIMARY TECHNIQUES USES X-RAYS TO STUDY METAL CONTENT.

Carlson: "Energy Dispursive x-ray flourescent analysis is a non destructive
technique which allows us to get a fairly complete elemental composition
of a metal alloy."

THE PROCESS STARTS BY AIMING X-RAYS AT THE METAL.  THE RAYS HIT
ELECTRONS AND GIVE THEM A KICK OF ENERGY.

Carlson: "As those electrons fall back down . . . they in turn emit their own
characteristic energies."

DIFFERENT ELEMENTS WILL ALL GIVE OFF DIFFERENT ENERGIES. AND SO
CARLSON CAN ANALYZE THESE EMISSIONS TO TELL EXACTLY WHAT TRACE
ELEMENTS ARE PRESENT.

Carlson: "So in this case. . .silver would be the primary element, but we
would see also copper and other trace elements and it's those trace
elements . . .which help us detemirne the authenticity of the particular silver
object." 

SHE CAN USUALLY PINPOINT BOTH WHEN AND WHERE THE PIECE WAS MADE. 
FOR EXAMPLE SILVER MADE IN THE COLONIAL U.SS IS USUALLY ABOUT 90%
PURE, WHILE BRITISH  SILVER FROM THE SAME TIME PERIOD IS CLOSER TO 92%
PURE.   ALSO, SINCE REFINING TECHNIQUES HAVE IMPROVED OVER THE
YEARS, OLDER SILVER HAS MORE TRACE ELEMENTS THAN DOES MODERN
SILVER.  THE SCIENCE HAS PAID OFF--CARLSON HAS GONE THROUGH THE
WINTERTHUR' S REVERE COLLECTION AND ROUTED OUT SEVERAL FAKES.