Iron objects with tin and gold inlays

Karin Abelskamp <k.abelskamp [at] archeologie__nl>

>In an excavation we carried out in the Netherlands, we have found
>numerous small objects.  Although most of them were completely
>covered with iron encrustations, they were recognized as belt
>mounts.  This was confirmed by radiography: beautiful decorations
>became visible on the fittings, buckles and buckle plates,  probably
>dating from the 6th century AD.

I would say it is very difficult question; before giving correct
answer, I would like to see your objects, X-rays etc. If you are
sure that your objects will be stored and exhibited at very dry
environment under 20% relative humidity, than desalination is not
necessary. But, are you able to guarantee these conditions?

Do you have some analysis of inlay metals?  Are you sure, that you
have, on your objects, tin (probably alloy Sn-Pb) and gold foil.
Wasn't whole object tin plated and then decorated by gold? If whole
objects have been tin plated, I will never use alkaline sulfite,
because you are not able to protect all parts and traces of tin
plating and during stabilization some remains of tin plating will be
dissolved.

I have to say, of course alkaline sulfite solution is very effective
method but also quite aggressive, especially for fragile objects. If
you would like to use alkaline sulfite, you have to be able to cover
the whole surface of the decoration and plating by a thick layer of
Paraloid B44.  After the evaporation of solvent, you have to have
glossy surface.

Sometimes, if objects are so complicated, I use only exchanged warm
demineralized water for desalination until chlorides concentration
falls to zero. The quality of desalination is much lower but you
can be sure that you are not dissolving decorations and metal
plating and its corrosion products.

Dusan Perlik
The Museum of Central Bohemia at Roztoky near Prague
Zamek 1
252 63 Roztoky
Czech Republic


                                  ***
                  Conservation DistList Instance 26:41
                  Distributed: Friday, March 15, 2013
                       Message Id: cdl-26-41-002
                                  ***