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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