Patinating copper

I am seeking input on options for the field patination of a copper
sheet dome.  A certain roof was cold-patinated 6 years ago but the
treatment has failed since then, yielding an uneven finish.  We are
exploring methods of generating a new green patina. Our ideal method
would be a treatment that immediately provides a compatible,
blue-green patina appearance (creating visual uniformity) which
eventually wears off while the natural patination process has taken
over--a system similar to what used to be called "Nordic Green" and
was available through a Finnish company called Outukumpu which was
purchased by another company called Luvata.  Nordic Green is no
longer available for purchase; it has been reissued as pre-patinated
copper sheeting form only.  The surviving literature says that the
primary ingredients of this product were: sodium hydroxide/sodium
chlorite; copper hydroxide nitrate; and sodium silicate
(waterglass).

In general, I am curious if anyone is aware of any examples of a
copper dome roof being field patinated, what products or chemicals
were used, and to what degree it was successful or unsuccessful.
More specifically, I am curious if anyone could comment on any past
experience working with Nordic Green as a field treatment.  In the
absence of this product, can anyone recommend a system that behaves
in a similar way?

I appreciate any input or ideas anyone might have on this subject.

Justine Posluszny
Assistant Conservator
Conservation Solutions, Inc.
503 C Street NE
Washington DC 20002
202-544-3257


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                  Conservation DistList Instance 21:27
                Distributed: Saturday, October 20, 2007
                       Message Id: cdl-21-27-026
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