Stephanie,

Corrosion intercept uses a scavenger impregnated into the polyethylene bag
matrix to absorb atmospheric pollutants. Usually it's a copper based
chemical. My concern, as a conservator, for composite objects, would be
maintaining the appropriate relative humidity for the organic components
such as wood, leather, textile, or ivory. Also since organometallic
corrosion between leather and copper alloys occurs by being in physical
contact with each other, storing in corrosion intercept bags would not stop
that problem.

Cheers!
Dave

David Harvey
Senior Conservator & Museum Consultant
Los Angeles CA
www.cityofangelsconservation.weebly.com
On Oct 9, 2013 11:25 AM, "Stephanie Skiles" <[log in to unmask]>
wrote:

> Hello All,****
>
> ** **
>
> This relates slightly to Kate McCarthy’s question about the waxy green
> buildup between metal and leather elements… ****
>
> ** **
>
> Our museum just purchased several “corrosion intercept pouches” for metal
> swords in our collection. Here’s a link to the pouches on University
> Products, if you are curious:
> http://www.universityproducts.com/cart.php?m=product_list&c=75****
>
> ** **
>
> We accidentally ordered too many of the pouches, and so we thought we
> could also use them for multi-media objects, such as horse tack that
> includes leather elements.  Has anyone out there used these pouches on
> items which contain metal and leather or other non-metal materials?  If so,
> did the pouch adversely affect the non-metal materials at all?  ****
>
> ** **
>
> Advice is greatly appreciated.  Thank you!****
>
> ** **
>
> Stephanie Gilmore****
>
> Anthropology Registrar****
>
> University of Colorado Museum of Natural History****
>
> ** **
>
> *From:* Museum discussion list [mailto:[log in to unmask]] *On
> Behalf Of *Kate McCarthy
> *Sent:* Wednesday, October 09, 2013 10:22 AM
> *To:* [log in to unmask]
> *Subject:* Re: [MUSEUM-L] Waxy green buildup?****
>
> ** **
>
> Friends thank you thank you thank you! The mineral spirits removed the
> waxy build up like a charm! A note has been in our files about treatment
> and future maintenance. Of course all our saddles need assessment by a
> conservator but for now the leather is consolidated and free of green waxy
> corrosion!
>
> Mary "Kate" McCarthy****
>
>
> On Oct 8, 2013, at 4:52 PM, David Harvey <[log in to unmask]> wrote:****
>
> Most saddle and tack "Silver"is made from Nickel Silver  (German Silver)**
> **
>
> *NICKEL SILVER*****
>
> A metal alloy of usually 60% copper, 20% nickel, and 20% zinc. It is named
> for it's silvery appearance, but contains no elemental silver unless
> plated. Another common name is* GERMAN SILVER*****
>
> Or from Monel which is a nickel copper alloy.****
>
> *MONEL*****
>
> Monel is a trademark of Special Metals Corporation for a series of nickel
> alloys, primarily composed of nickel (65-70%) and copper (20-29%), with
> some iron and magnanese (5%) and other trace elements.****
>
> Cheers!
> Dave****
>
> David Harvey
> Senior Conservator &* *Museum Consultant****
>
> Los Angeles CA****
>
> www.cityofangelsconservation.weebly.com****
>
> ** **
>
> On Tue, Oct 8, 2013 at 1:06 PM, LINDA ELLIS <[log in to unmask]> wrote:****
>
> Hello Mary,
> Many saddles, stirrups and other riding gear have metallic attachments
> that are made of nickel (dull silver color).  The major corrosion product
> of nickel is nickel sulphate, which can be dark to bright green.  The
> sulphur may come from the tanned leather itself or any cleaning/polishing
> materials.  Fortunately, nickel sulphate is easily removed.  What I have
> done for my collections in the same situation is cut a small piece of thin,
> bendable plastic (no sharp edges) and place it between the leather and the
> metal attachment, so that there is no physical/chemical contact between the
> metal and the leather. ****
>
> ** **
>
> Prof. Linda Ellis
> Senior Curator, University Museum, SFSU
> Founding Director [1987-2011], Museum Studies Program
> San Francisco State University
> Member: New York Academy of Sciences****
> ------------------------------
>
> *From:* Museum discussion list [[log in to unmask]] on behalf
> of David Harvey [[log in to unmask]]
> *Sent:* Tuesday, October 08, 2013 12:08 PM
> *To:* [log in to unmask]
> *Subject:* Re: [MUSEUM-L] Waxy green buildup?****
>
> Mary -
>
> Most saddles and tack not only have residues from saddle soap but also
> oils used as leather dressings over the years. It is common to find a waxy
> green corrosion product where copper alloys are in contact with leathers
> and  skin. Organometallic corrosion results from fatty acids, primarily
> steraic and oleaic acid, which dissolve copper ions from leathers and
> skins. You also will see this on rings and jewelery that people wear,
> glasses too, as well as on brass tacks on old leather covered trunks.****
>
> Most of the time it comes off easily with swabs moistened with mineral
> spirits. But it is an inherent condition and will continue as long as the
> metal and leather are in contact.****
>
> A larger issue is all that gunk from the soap and dressings on the
> leather. Often they are a great food source for fungi (mildew and mold)- so
> you may see white, black, or orange blooms appear. The organic oils will
> eventually chemically crosslink and darken the leather, and eventually it
> may become very brittle.
>
> This is where you need a knowledgeable objects conservator to examine the
> leather saddle to assess it's condition and make treatment recommendations.
>
> Cheers!
> Dave****
>
> David Harvey****
>
> Senior Conservator & Museum Consultant****
>
> Los Angeles CA****
>
> www.cityofangelsconservation.weebly.com ****
>
> ** **
>
> On Tue, Oct 8, 2013 at 11:33 AM, Kate McCarthy <
> [log in to unmask]> wrote:****
>
> Ok this one's for the conservators and leather goods folks on here. I work
> at a Western history museum and we are getting a selection of saddles ready
> for exhibit. However, I've noticed a nasty dark green waxy build up on one
> of the saddles wherever metal touches leather. This saddle may have been
> treated with saddle soap at some point and has almost certainly been
> polished with Renaissance wax at some. The leather does feel sticky to the
> touch. Does anybody have an idea about a) what is this green waxy build up?
> B) how do I get this stuff off the metal parts without damaging the
> leather? C) can I prevent it from coming back?
>
> Thanks y'all!
>
> Mary "Kate" McCarthy
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