Insoluble salts on tanned leather

We are working on a 19th century saddle made of tanned leather. The
leather is altered and extremely dry and cracked. It is also covered
with a white efflorescence. After a series of tests, we think that
this efflorescence is an insoluble salt even though we have not yet
identified it and are not sure if it originated from the tanning
procedure.

Has anyone experience in treating insoluble salts on tanned leather
objects? Would it be preferable to apply a specific solvent or a
complexing agent? We made some tests with sodium hexametaphosphate
on a cotton swab with immediate rinsing with distilled water. It
seems to give the best result but we don't know if this treatment
could have undesirable consequences for the leather. We would be
grateful to hear of any past experiences on similar artefacts. Thank
you for any explanation,

Salome Guggenheimer
Jana Egger
Students in Conservation
Haute Ecole d'Arts Appliques He-Arc
La Chaux-de-Fonds
Switzerland



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                  Conservation DistList Instance 18:33
                 Distributed: Sunday, January 23, 2005
                       Message Id: cdl-18-33-028
                                  ***