Bronze

This enquiry is made on behalf of a conservator not on the list. The
conservator was involved in a major project involving the treatment
of a number of large (approximately 10 x 20 foot) bronze frames
surrounding external windows on a building of some historical
importance. The site itself is in a prominent position on a south
coast seafront.

The bronze frames were treated in situ, and after removal of all the
verdigris covering the frames conservators applied two coats of the
lacquer known as Incralac to the cleansed and supposedly completely
dry surfaces.

The initial coats appeared to have taken well but in the last eight
months a green mottling has appeared underneath the lacquering and
appears to be worsening.

The question raised by the conservator is whether salt (from a
century of sea air/water pounding) could have penetrated the pores
of the bronze and whether it might now be being released to
contaminate the surface below the lacquered surfaces.

The conservator mentions that he has heard of similar instances with
old anchors where salt in the pores released to cause patination
after preservation. Any ideas as to what might be happening would be
appreciated and will be relayed to the conservator in question.

Mark G. Vine
Conservation Resources
England

                                  ***
                  Conservation DistList Instance 12:87
                  Distributed: Thursday, May 13, 1999
                       Message Id: cdl-12-87-017
                                  ***