Hi John,Thanks for the I used your magnet trick to
be sure my spoons and forks do have enough iron to work ok.
The objects I am learning how to clean are ancient bronze seals
(about 4000 years old), and the corrosion is very hard in some
places and quite thick. I experimented first with an old corroded
coin about 2000 years old. It
was relatively easy to clean, but the corrosion didn’t approach
that of some of the old seals. My main guide in this project has
been Plenderleith’s book on “The Conservation of Antiquities and
Works of Art”. It’s an excellent book but doesn’t cover all the
little situations I am encountering.
Anyway the seal I am working on is disc shaped and about two
inches in diameter. I have been treating it at about 2-4 amps (the
maximum from my machine) which is about what I think Plenderleith
recommends. Nonetheless, I have developed a problem with the seal
which Plenderleith says is caused by too little current: some
small amounts of a white metal have redeposited on
the bronze seal. Hopefully, they will go away if I watch the
process closely, keep the amps up. and clean things a litle more
often.
Thanks again for your help and I welcome any other suggestions,
Regards,
Ron
Hi John,Thanks for the I used your magnet trick to
be sure my spoons and forks do have enough iron to work ok.
G’day again Ron: I think you mistook my note; stainless steels
used as electrodes should NOT have any iron included in their
composition! If the stainless is attracted by a magnet then it
probably DOES contain iron and shouldn’t be used. Having said
that, some high grade stainless alloys of cobalt and chromium are
very slightly magnetic, but I doubt that they would cause any
problems when used as deplating or stripping electrodes. Do you have
an ultrasonic cleaner? This when used with a hot alkaline
detergent solution gives excellent results without abrading the
valuable old artefacts and is a good degreasing agent. To remove
some oxides and sulphides coating certain metals you could try
having a small piece of aluminium sheet in a vessel of hot alkali;
like a solution of sodium carbonate (common washing soda crystals)
This produces a stream of nascent hydrogen gas which is very active
in combining with oxides, producing water and leaving the metal
clean. With bronzes, a quick wash of hydrochloric acid will
dissolve oxides, and if the acid isn’t left in contact with the
bronze for more than a few seconds, no harm should result - but try
this in a place which isn’t important. Cheers now,
/\
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/ / @John_Burgess2
/ /___| \ at sunny Nelson NZ
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