Kelli,
 
I agree with the info in the other posts but would like to add that, I have now seen these bags (poly) -regardless of thickness and proper storage, after a decade+ and even lesser periods of time...appear to 'break down'. They harden and seem to become fragile.
 
There are many factors, other than thickness alone which may determine how permeable they are, such as how they are sealed and resealed (firmly/airtight..if there's any moisture in the bags to begin with) and if they are stored tightly with other bagged objects and in a container which allows for airflow, how often they are handled, etc.
 
That being said...one of the other benefits of clear bags of course, is that you can view the contents without opening the bag and removing them. However, with the exception of lithics (generally), I have always lightly wrapped objects in acid free, ph neutral and/or cotton batting (depending on the composition of the object) as a buffer to further protect/preserve/stabilize the bagged objects.
 
I have re-bagged objects using newer bags in as few as 3-4 years..but as I recall they had been stored in a too cold (even freezing) environment.
 
Pam
 
In a message dated 8/13/2007 4:39:11 P.M. Eastern Daylight Time, [log in to unmask] writes:
For my second question of the day, when bagging artifacts (of any kind) for
storage, is there a museum standard for the thickness of the bag?  2mm, 3mm,
4mm, etc.?  Thanks again for any responses.

Kelli

*********************************
Kelli Bacon
Nebraska State Historical Society
1500 R St.
PO Box 82554
Lincoln NE 68501-2554
402-471-4766
[log in to unmask]
www.nebraskahistory.org
 



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