I am responding to Ivy Strickler's query concerning "pure silver".

It would be extraordinarily rare to find pure silver from any kind of
historic or ancient artifactual context.  Until relatively recent times most
silver was extracted from lead containing ores by cupelation in furnaces.
 The silver product could be then alloyed with copper to different purities
(ie.,  standards).  There is always some trace amounts of lead and usually
gold present in silver/copper alloys produced by this technology.

Even if "pure silver" were present in an artifact it would still likely
tarnish if exposed to suphides, such as those found in our modern air, or in
natural and synthetic rubber compunds, and even wool fabrics.  Silver is also
likely to tarnish and etch when exposed to chloride salts. I have seen
numerous pieces of silver with blackened fingerprints etched deep into the
surface of the object.  Silver/copper alloys can also suffer severe copper
corrosion due to galvanic coupling - where dissimilar metals are joined
together such as solder joins. Ancient silvers undergo an internal
microscopic form of corrosion in which copper forms a discontinuous
preciptation along the metal grain boundries - this leaves the artifact in an
extremely fragile and brittle condition.

My best advice is: If it looks like it's in great shape then leave it alone!
   If you have a serious research interest in studying the piece to ascertain
it's composition then there are several non-destructive methods of analysis
which might be utilized with a known standard for comparison and
quantitation.

Our conservation department has developed a series of "Caring For Your
Collections" brochures on various media (ie., silver, copper alloys, tin
alloys, iron, firearms, furniture, upholstery, musical instruments,
paintings, glass, ceramics, paper, quilts and coverlets, and archaeological
objects).  These are free and availiable upon request.

Dave

David Harvey
Conservator of Metals & Arms
Colonial Williamsburg Foundation
P.O. Box 1776
Williamsburg, VA 23187-1776   USA
voice:      804-220-7039
e-mail:   [log in to unmask]