Sulphamic acid

Neil Mahrer <neil.mahrer [at] jerseyheritagetrust__org> writes

>...  He is also keen to give us a large amount of
>sulphamic acid which he has used for some years in the
>cleaning/stripping of recovered copper and brass items. ...
>on its possible use before I respond to his offer.

In my years working as an archaeological conservator we generally
tried to avoid chemical stripping treatments on metal objects (there
were a few exceptions depending on the metal, and the situation of
course). It is nearly impossible to wash off every trace of the
stripping chemical from the porous surfaces of archaeological metal,
so in the long run the chemicals tend to promote corrosion of the
treated object. The other reason we avoided it is that chemical
stripping is more difficult to control than mechanical methods (a
chemical doesn't stop acting until you wash it away, but a
micro-abrasive pen stops the instant you point it away from the
object). With most archaeological objects, you don't want to remove
all the corrosion, just the stuff down to the original surface.
There may not even be any metal left in an archaeological "metal"
object.

So the short answer is: I never used sulfamic acid for such purposes
in my 6 years at the bench with archaeological objects.

Valerie Tomlinson
former conservator


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                  Conservation DistList Instance 20:21
                Distributed: Wednesday, October 18, 2006
                       Message Id: cdl-20-21-005
                                  ***