Carolyn,
 
There are several ways of using ziploc bags and to avoid the condensation
problem. One simple way is place the artifact in a small acid-free tray
and to place the tray inside of a ziploc bag which has been perforated
multiple times with a sharp probe. This will allow a certain amount of
equilibrium between the outside air and the artifact.
 
There are many artifacts which should not be exposed to rapid changes in
relative humidity (especially organic archaeological finds). In this case you
would want to utilize silica gel which has been preconditioned to a
specific RH and to include this (along with an RH indicating card or
meter) inside of the sealed container. In this instance a controlled
microclimate is desirable until the artifact can be examined by a
conservator. Wet or very damp terrestrial archaeological artifacts can
be stored by being wrapped with an inert polyester fabric and kept
damp/wet. I have seen paper towels used for this purpose and that
always creates a mess.  In all cases try to store by media - if this is
problematic then you have to establish storage conditions best suited
for the most sensitive material that you have. See A Conservation Guide For
Field Archaeologists by Catherine Sease, it's put out by UCLA press I
believe.
 
The brown paper bags which are used by many folks can cause severe damage
to  artifacts which are sensitive to organic acids - such as lead and
lead  alloy artifacts. The brown bags should only be seen as a very
temporary  storage situation if you are moving artifacts from the field
to the lab.
 
In this, as in all cases, it is best to compare notes with a wide
spectrum of people and to learn the pluses and minuses of any storage
system or media.
 
Best Wishes,
 
Dave
 
 
David Harvey
Conservator of Metals & Arms
Colonial Williamsburg Foundation
Williamsburg VA 23187-1776
804-220-7039
 
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