Ammonia treatment for red-rotted leather

The furniture conservation staff at the Philadelphia Museum of Art is
considering treating some late-19th C leather-covered chairs and
footstools.  The leather is vegetable-tanned and quite acidic and
consequently red-rotted.  We would like to reduce the acidity and are
considering a short exposure to ammonia fumes (reacting with the
sulfuric acid in the leather to form ammonium sulfate), the main method
discussed in the literature.

Complicating our decision-making about these objects is the fact that
they have painted and silver-leafed surfaces as well as horsehair
stuffing.  We will not be able to remove the leather from the articles.
Despite our general hesitancy toward exposing the metal leaf to ammonia,
we are somewhat encouraged by the fact that the natural resin varnish
coating the leaf has so far kept the leaf from tarnishing and thus may
well stand up to a short exposure to ammonia.

We have noticed the recent discussions of leather issues in the DistList
and wondered if perhaps our problem might be similar to something you
book people out there have encountered and successfully treated.   We
would greatly appreciate any comments you may have.

Peter Eastman
Assistant Conservator of Furniture
Philadelphia Museum of Art
26th and Benjamin Franklin Parkway
Philadelphia, PA 19130
(215) 684-7556

                                  ***
                  Conservation DistList Instance 7:70
                  Distributed: Thursday, April 7, 1994
                        Message Id: cdl-7-70-006
                                  ***