Hi Laura,
CHM uses U-Line food grade polyethylene bags. They are excellent in
quality and come in a huge variety of sizes at a fraction of the cost
the 'archival' suppliers provide. U-Line will answer any questions you
have about their manufacturing methods or sub-contracted materials.
Bonus: they'll send samples too. You are wise to ask questions! From
personal experience I always keep in mind that there is no
"international standard" for the term 'archival' and any vendor can
apply it any way they see fit.
-Karen
<><><><><><><><><><><><><>
Karen Kroslowitz, Registrar
Computer History Museum
1401 N. Shoreline Blvd.
Mountain View, CA 94043
v: 650-810-1022
f: 650-810-1055
e: [log in to unmask]
<mailto:[log in to unmask]>
w: www.computerhistory.org <http://www.computerhistory.org>
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________________________________
From: Marc A Williams [mailto:[log in to unmask]]
Sent: Monday, May 11, 2009 9:33 AM
Subject: Re: polyethylene bags--sources and different types
Laura,
First, let me say I am a pragmatist, not an idealist, at least with
respect to conservation. The answer to your question is it depends,
both on the product, as well as what you are using the bags for.
Polyethylene itself is stable and considered appropriate for
conservation use. However, not all polyethylene is made the same way.
Some have additives and is mostly polyethylene, but it is still called
polyethylene. Some have excess ethylene monomer or catalyst that are
left over from the conversion to polyethylene. How much of this exists,
who knows. I personally doubt that the archival suppliers have any
better handle on this than anyone else.
So, my general rule (of course subject to inaccuracy) is that if
something is food grade - it is suitable for food that ends up in our
bodies, it is OK for museum collections. This is not perfect, as
evidenced by the recent controversy over water and drink bottles that
are made of polystyrene and polycarbonate, and may be OK for short term
use, but can be dangerous if re-used over and over. I have always felt
it was OK to use food-grade polyethylene bags for collections,
particularly for those institutions who want to get the most bang for
the buck. I'm sure others may disagree, but we certainly can't be
testing every bag we use for a bad batch or other inappropriate
manufacturing techniques. At some point, we have to put our faith in
something, and I think that companies that produce a product that could
make people sick and result in huge lawsuits have an incentive to be
pretty careful in their quality control, at least compared to companies
that make archival products which have very little risk of resulting in
lawsuits.
These same considerations also apply to "ethafoam," which is itself made
from polyethylene. If the commercial variety of ethafoam is OK compared
to the "archival" variety, then the commercial bags should also be OK
also. As for the U-Line bags, the description of "100% virgin, high
clarity polyethylene film" would suggest that further investigation is
needed. Polyethylene generally has a cloudy appearance. In order to
produce more clarity, commonly additives are mixed in. If this is the
case, they may leach out over time, such as the concern with Bisphenol
A. If the bags are 100% polyethylene with no additives, they should be
fine. The phrase "100% virgin, high clarity polyethylene film" can be
interpreted to read that the polyethylene that is present is 100%
virgin, but not necessarily that 100% of everything that is present is
polyethylene. Good luck sleuthing!
Marc
American Conservation Consortium, Ltd.
4 Rockville Road
Broad Brook, CT 06016
www.conservator.com
860-386-6058
Marc A. Williams, President
MS in Art Conservation, Winterthur Museum Program
Former Chief Wooden Object Conservator, Smithsonian Institution
Fellow, American Institute for Conservation (AIC)
----- Original Message -----
From: Laura Bachelder <mailto:[log in to unmask]>
To: [log in to unmask]
Sent: Monday, May 11, 2009 10:41 AM
Subject: [MUSEUM-L] polyethylene bags--sources and different
types
Good Morning-
I noted the discussion about sources for polyethylene foam last
month with interest. I was stunned (and grateful) to find that what I
had been buying from an archival supply company, I could get for less
than half the cost though U-Line. This led me to compare the
polyethylene bags and enclosures that we use for photos, documents and
small artifacts.
At this point I would love some advice from the conservators on
the list. Is U-Line's poly bag (100% virgin, high clarity polyethylene
film, 2 mil) really an equal product to Archival Methods uncoated
polyethylene, chemically inert bags? I'm having difficulty determining
what specifications I should be asking for. It seems too easy (given
their prices) that U-line's bags would be on par with the average
Archival supplier.
Thanks,
Laura (Bachelder) Furman
Curator of Collections
Midway Village Museum
815-397-9112 ext 108
815-397-9156 fax
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