I have noticed "spue" in both books and other leather objects. Is it
harmful to people or the item in question?
Thanks
Senjit
At 12:18 PM 1/20/00 -0800, you wrote:
>Responses to my posting about what precipitates "spue" prompted more
>questions about "what is it" than it did about "when does it." Here's a
>summary:
>
>Spue is a white fine powdery odorless residue that appears on the
>surface of leather bindings (not to mention saddles and other treated
>leathers), looks similar to mold but shows a more even, uniform coating,
>and is either salt or oxidized fat that exude from the leather under
>"certain atmospheric conditions." Often, the salts and fats come either
>from poor tanning [rarely] or, more likely, from inappropriately applied
>leather dressings that contain things like Neatsfoot Oil or potassium
>lactate--these were and are quite commonly applied, and their use is
>highly controversial within the preservation community.
>
>When the surface of the leather has more moisture than the interior mass
>of the leather, the leather rejects the dressing (or the salts leach
>out) and the result is lingering crystalline structures that remain on
>the surface until they are physically removed. More subtle atmospheric
>conditions, like pH and particulate contaminants, may also play a role.
>
>The salt residues brush right off; the fatty residues are obviously oily
>and tend to demand rubbing/buffing to improve the appearance.
>
>Salt spue dissolves in water and has microscopic crystalline structure;
>fatty spue melts when heated (no, I didn't try THAT test); molds exhibit
>none of those characteristics or reactions. Nor does mold typically
>present in low humidity exclusively on selected leathers (e.g., we have
>a six-vol. set of which v.4-6 show the residue profoundly while v.1-3
>are unaffected--apparently only half the set was treated).
>
>Contamination of adjacent items is not an issue.
>
>Recurrence is common. One librarian has actually established a regular
>"wiping" program as part of his stacks maintenance operation because the
>same volumes repeatedly "bloom" from time to time.
>
>The literature is pretty anemic about this--see Abbey Newsletter, v.21,
>no.2 (July 1997) for chemistry; http://www.hewit.com/sd2-bloo.htm for a
>readable survey; discussion on Consdistlist listserv [all available on
>CoOL site at: http://palimpsest.stanford.edu/]
>
>In our case, the catalyst might have been a mid-December anomalous,
>precipitous drop in our stacks air temp. (15 degrees within 24 hours),
>which might have loaded sufficient extra moisture on the exposed binding
>surfaces to trigger the process. But we still don't really know.
>
>Richard Lindemann
>Director, Special Collections & Archives
>Bowdoin College Library
>rlindema@bowdoin.edu
>