Oil staining

I am presently treating a mid-late 19th C Hudson River School
landscape.   In the sky are noticeable areas of "oil staining" which
correspond with the weave of the canvas; a sort of grid pattern if
you will.  This material is rather discolored and visually
distracting.  It fluoresces a pale yellow-orange in UV which
corresponds to the fluorescence of stand oil.  I am attempting to
research this phenomenon.  I have discovered that while many
conservators are familiar with this type of "staining," (it has
been noted on works by Winslow Homer as well as other 19th artists)
there is little to no mention of it in the literature.  Does anyone
know of any published or unpublished research or papers?  Any
thoughts on causes?  Solutions?  Similar experiences?  I am
interested in anything that may enlighten my understanding of this
phenomenon. Thanks,

Charlotte Seifen
Painting Conservation
The Fine Arts Museums of San Francisco

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                  Conservation DistList Instance 12:46
                 Distributed: Monday, November 23, 1998
                       Message Id: cdl-12-46-012
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