Subject: Re: Electrolytic Derusting?

From: Richard Hager <[email-masked]>
Date: Wed, 24 Apr 1996 17:17:07 -0400

Marc Line wrote:

> I'm interested in electrolysis for the removal of patina from 2000 year old copper Roman coins.  Perhaps if anyone can help Chris they 
could help me at the same time?  Two birds with one stone as it were!
> Cheers
> Marc Line

-- 

Hi Marc,

In printed circuit board fabrication, it is very common to 'microetch' 
the pcb surface prior to applying dryfilm resist, plating, etc..

Several solutions are used.  One is simply a 5-10% sulfuric acid 
solution in distilled water.  Another is sodium persulphate.  Another 
is ammonium persulphate.  The last two are white crystals that you 
dissolve in water.  The persulphates are fairly commonly available from 
hobby electronic stores.

Notes:

-ALWAYS use eye protection when working with chemicals and solutions.

-If diluting the sulphuric acid yourself, be careful!  Go slowly.

-Remember that you are not really cleaning copper coins.  You are 
cleaning copper -alloy- coins.  It's quite likely that the coins 
contain a number of other metals, including arsenic.  You may generate 
poisonous solutions and vapors while doing the etching.  Also, any 
etchant bath designed for copper may not work as expected on these 
coins.  I'd try a less valuable sample -first-.

-In regards to cleaning them electrolytically, I'm not sure why that 
would be neccesary.  However, you could try a simple copper sulphate 
solution (avail at hardware store for root killing in drainpipes).  You 
may need to add a little sulfuric acid for conductivity also.  I'd try 
the microetch baths first however.

Good luck!

        Richard Hager

-  Ah-ha! Design Group, Inc.     +
-  Affordable Precision CNC       +
-  612-641-1797, fax: 641-8681     +
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-  www.gdic.com/ahha  [email-masked]   +

---

From: [email-masked] (Randall Bradley)
Date: 29 Apr 1996 16:09:33 GMT

I'd make some phone calls before I dunked any coins in anything.

Try some museums, the Met in NYC, the Smithsonian in DC, or some
more local. Top line coin dealers will know the ins and out's too
(probably). I'd get several opinions from folks who have worked
with Roman coins in SPECIFIC, find some agreement, and then proceed
with a less valuable piece(s) first. Or, perhaps they'll even
do the job for you!

			_-_randy_-_

			BEAR Labs

			[email-masked]

"We make high-end audio stuff called BEAR, we don't test bears!"