Thank you Scott for the clarification: There was no corrosion caused by the vapors of the polyethylene foams in our tests. We specifically have half of our coupons touch the material and half of it just exposed to vapors (i.e no contact). This way we could clearly observe the corrosion when in contact. The areas on the coupons that did not touch the foams were in very good condition.
We also tested Volara -a fine-celled cross-linked foam, and observed that it did not corrode the metals when in contact or no contact. Therefore we use it as a layer between the object and open-celled polyethylene foam products. Moreover, it has a smoother surface which does not abrade the surfaces of hard objects.
Ozge
On Feb 27, 2012, at 11:20 AM, [log in to unmask] wrote:
> The article entitled "Polyolefin Foams" in the New Materials and Research
> section, beginning on page 26, of AIC News, January 2002, found at
> http://www.conservation-us.org/_data/n_0001/resources/live/02_jan_aicnews.pdf
>
> has a more up-to-date and complete discussion of my views on polyethylene
> foams.
>
> Ozge makes a very pertinent statement: "During our several Oddy tests we
> found that when in contact with metal coupons the foam (especially the thin
> sheets, not the thick plank ones) leave zebra imprints and cause
> corrosion." Many others have reported this pattern of contact corrosion.
> Presumably, because he does not mention it, corrosion by vapours in tests
> where there was no contact did not occur, even at the high humidity
> required for the Oddy test. The key here is that corrosion occurred when
> there was contact between the metal and the foam, and probably it is
> important also that this test is done at high humidity. I agree that
> permeability agents are a possible cause of contact corrosion at high
> relative humidity. I am not so sure if they are a problem in dry
> conditions, or that they are volatile enough to cause vapour phase
> corrosion such as measured by the Oddy Test for volatile corrosive
> products. In any case, Ozge's decision to avoid direct contact of thin
> polyethylene sheets with metals is certainly safe. I am curious to know
> what he uses as a "layer that doesn't affect metals".
>
> Remember that, unless they specifically mention contact experiments (as
> Ozge did), when people report the results of Oddy Tests, they are
> reporting on the corrosion caused by volatile corrosive products emitted by
> the tested material, and not the results of corrosion caused by contact
> with the tested material. These are two very different conservation and
> corrosion scenarios. I think a dilute sodium chloride solution would pass
> the Oddy Test (no corrosion of metal by vapours from the solution), but it
> would certainly corrode metals by contact.
>
> Scott Williams
> Senior Conservation Scientist (Chemist)
> Canadian Conservation Institute
>
> Textile Conservators <[log in to unmask]> wrote on 2012-02-24
> 04:16:04 PM:
>
>> From: Ozge Gencay Ustun <[log in to unmask]>
>> To: [log in to unmask]
>> Date: 2012-02-24 04:16 PM
>> Subject: Re: Ethafoam
>> Sent by: Textile Conservators <[log in to unmask]>
>>
>> Part of the question started because of our Oddy Test findings here at
>> the Southwest Museum, Autry National Center. Some of our metal objects
>> are in close contact with thin polyethylene foam sheets (source
>> unknown). Therefore we started to test some of these polyethylene
>> foams (Ethafoam, Cellu-Cushion and ones from unknown sources). During
>> our several Oddy tests we found that when in contact with metal
>> coupons the foam (especially the thin sheets, not the thick plank
>> ones) leave zebra imprints and cause corrosion. Some people I talked
>> to were concerned about the permeability agent used in thin
>> polyethylene sheets and Scott Williams of CCI did some research about
>> this. We concluded that it was OK to use thin polyethylene sheets on
>> organic objects and on glass and ceramics, but when in direct contact
>> with metals (polished or not) we use a layer that doesn't affect
>> metals.
>>
>> Özge Gençay Üstün
>> Assistant Conservator
>> Southwest Museum of the American Indian
>> Autry National Center of the American West
>> 234 Museum Drive
>> Los Angeles, CA 90065
>> Phone: (323) 221-2164 x250
>> Fax: (323) 224-8223
>> [log in to unmask]
>>
>>
>> 2012/2/24 Ann Frisina <[log in to unmask]>:
>>> If you are speaking of a yellowing which occurs within closed
>>> cell polyethylene foam planks then Scott Williams of CCI spoke about
> this
>>> issue back in 1998. Below is a link to his detailed explanation.
>>>
>>> http://cool.conservation-us.org/byauth/williams/foam.html
>>>
>>> Best
>>> Ann Frisina
>>> [log in to unmask]
>>>
>>>
>>>
>>> On Fri, Feb 24, 2012 at 9:23 AM, Evans, Sunae Park <[log in to unmask]>
> wrote:
>>>>
>>>> There were discussions about the quality of Ethafoam at the end of the
>>>> last May. Our museum uses Dorfman Conservation Forms made of
> Ethafoam and
>>>> also heavily uses Ethafoam for various purposes, so I am
>> seriously concerned
>>>> about the quality of the foam. I contacted Rob Dorfman of Dorfman
> Museum
>>>> Figures, Inc., and John Dunphy from University Products about this
> issue.
>>>> They immediately talked to Troy Kimball from Sealed Air. I talked to
> him
>>>> about my concerns, too.
>>>>
>>>>
>>>>
>>>> I received an e-mail from Penny Clifton from Dorfman Museum Figures
>>>> yesterday and would like to share information with you.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> Sunae Park Evans, Senior Costume Conservator
>>>>
>>>> Smithsonian Institution
>>>>
>>>> National Museum of American History
>>>>
>>>> Preservation Services, MRC 642
>>>>
>>>> P.O.Box 37012
>>>>
>>>> Washington, DC 20013-7012
>>>>
>>>> 202)633-3629 or 3630
>>>>
>>>> 202)786-2154 (fax)
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> ---------- Forwarded message ----------
>>>> From: Penny Clifton <[log in to unmask]>
>>>> To: "Evans, Sunae Park" <[log in to unmask]>
>>>> Cc:
>>>> Date: Thu, 23 Feb 2012 15:57:46 -0500
>>>> Subject: Ethafoam Oddy test
>>>>
>>>> 2/23/12
>>>>
>>>> Dr. Sunae Park Evans
>>>>
>>>> Senior Costume Conservator
>>>>
>>>> National Museum of American History
>>>>
>>>> Kenneth E. Behring Center
>>>>
>>>> PO Box 37012 MSC642
>>>>
>>>> Washington, DC 20013-7012
>>>>
>>>>
>>>>
>>>> Hello Sunae:
>>>>
>>>> I hope this letter finds you well. We have been diligently working
> with
>>>> Sealed Air Corporation in the past few months to clear up any
>>>> misunderstanding surrounding Ethafoam® and its credibility as an
> inert,
>>>> conservation-quality foam, particularly as shown by the Oddy test. To
> that
>>>> end, we would like to share with you the technical information that
> was
>>>> provided to us by Sealed Air Corporation.
>>>>
>>>> Please click
>>>>
> on http://www.sealedairspecialtymaterials.com/na/en/pdf/oddytest.pdf to see
>>>> the results.
>>>>
>>>> We would appreciate your sharing it with any interested parties.
> Please
>>>> contact me or Robert Dorfman if you have other concerns or questions.
>>>>
>>>> Warmest Regards,
>>>>
>>>> Penny
>>>>
>>>>
>>>>
>>>> Penny Clifton, Project Manager
>>>>
>>>> Dorfman Museum Figures, Inc.
>>>>
>>>> 6224 Holabird Ave.
>>>>
>>>> Baltimore, MD 21224
>>>>
>>>> 800-634-4873
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>> --
>>> Ann Frisina
>>> Textile Conservator
>>> Minnesota Historical Society
>>> 345 Kellogg Blvd. W.
>>> St. Paul, MN 55413
>>> 651 259-3385
>>>
>>> http://www.mnhs.org/preserve/conservation/index.html
>>>
|
