Cleaning metal

Melissa Marsh Heaver <mmheaver [at] aol__com> writes

>In my spare time, I am on the Vestry of my local church. We have a
>nickel and silver alloy cross, c. 1957, that hangs from the ceiling.
> ...
>
>It has been taken down for Lent, and stored. We hope to have it
>cleaned and probably relacquered, as it hasn't been down in at least
>15 years. The local person the church wants to do the job is
>suggesting that it be cleaned via "sand-blasting", but with glass
>beads. Is this a wise idea, or will we be removing metal? If this
>method isn't a good idea, is there anything else we can use to clean
>it and get the grunge off?

I have to say that, while metals are not my strongest area of
expertise, the suggestion of cleaning the metal via "sand blasting"
be it with glass beads or any other material, is simply mind
boggling to me. I have to raise the question; Is this "local person"
a conservator? If the answer is yes, I would find another
conservator (run don't walk). Bad, bad, bad "local person".

First, if the cross is already lacquered, then what you are really
trying to clean is the coating. You have to find out; what it is you
are trying to clean off, and what are you trying to clean it off
from. If the coating is compromised due to age (and I would expect
it to be failing at this age if it is a nitrocellulose lacquer) or
any other reason, you just have to chemically remove the coating,
and the foreign matter ( grunge) will be gone also. Then deal with
whatever remains. If it is tarnished, polish it.

We typically would use a much less abrasive choice of material, such
as precipitated chalk to polish, and/or a 10% solution of formic
acid in distilled water to clean. Then cleared well with distilled
water. You will want to consider recoating after cleaning, perhaps
with Agateen, to protect it from tarnish and pollutants. Hopefully
some metal conservators will chirp in and provide other options.

Wendy Leeds
Deller Conservation Group
Geneva IL USA


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                  Conservation DistList Instance 17:63
                  Distributed: Tuesday, March 30, 2004
                       Message Id: cdl-17-63-003
                                  ***