Taking molds for reproduction of metal objects can be done with an RTV
(room temperature vulcanizing) molding compound, thus eliminating any
heating effects on the objects. You can contact Dow Corning Moldmaking
division (517-496-4400) as well as GE Silicones technical assistance
(800-255-8886). They should each have products that will perform well
and their tech people should be able to advise you. Another prudent call
to make would be to the Getty Conservation Institute (check their web
site for number) to get their recommendations as they probably have the
best information on any possible reactivity and special needs.

Good Luck

Jamie Hascall
Mount Specialist
Hascall Museum Services
Seattle, WA
[log in to unmask]