German silver parallel rule

Hilary Wright <hilarymwright [at] hotmail__com> writes

>I am about to conserve a parallel rule, a surveying instrument made
>in the UK towards the end of the 19th century and sold in Australia
>where it now is. There appear to be some copper coloured "corrosion
>products" on it at intervals but otherwise the rule is merely dull.
>The curator would like the finished effect to be corrosion free
>though not very shiny and to be lacquered to prevent further
>deterioration. Has anyone any experience in dealing with German
>silver (nickel silver)? Is the copper colour indeed copper due to
>loss of nickel? What does anyone advise on cleaning and protective
>coating?

The copper colour could be due to loss of nickel, or plating out of
copper on the surface. In either case you'll probably find that the
copper layer is relatively thin. You might like to try to remove the
copper colour by swabbing with dilute ammonia, followed by a
thorough washing in clean water, and coat it with Incralac or a
microcrystalline wax. Alternatively, you could polish it off,
although this will result in the shiny appearance that you are
trying to avoid. In this case I'd coat it with a matt lacquer, such
as Frigilene.

George Bailey
Objects Conservator
Australian War Memorial
PO Box 456, Canberra, ACT
Australia
+61 2 62434436
Fax: +61 2 62417998


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                  Conservation DistList Instance 14:4
                 Distributed: Wednesday, July 12, 2000
                        Message Id: cdl-14-4-001
                                  ***