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Author Topic: To strip, or not to strip, Sev Alex?  (Read 1007 times)

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Offline Ken W2

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To strip, or not to strip, Sev Alex?
« on: September 08, 2020, 09:28:39 pm »
I believe this is a Sev Alex of Niicea. The surface is a little rough, but is stable and cleaned of most dirt. My thought is nothing short stripping it to bare metal and darkening with liver of sulphur will improve it, and even that might not improve it much or any. I don’t see many provincials in uncleaned lots so even if it’s a common coin I like to keep it from the discard pile. I’d appreciate your thoughts on how this coin can be improved.
Ken

Offline v-drome

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Re: To strip, or not to strip, Sev Alex?
« Reply #1 on: September 08, 2020, 10:54:37 pm »
I would not strip it without trying other things first.  Here is a similarly corroded coin, before and after, with just a day's soak in Olive Oil.  It darkened and somewhat evened out the color.  I think if you strip it you will have lots of pitting and less detail, but I am interested in any other opinions.  Good luck with this one!

Offline Mark F

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Re: To strip, or not to strip, Sev Alex?
« Reply #2 on: September 10, 2020, 10:59:07 pm »
Ken,

No doubt about it - that's a butt-ugly coin.  ;-)

I see very patchy patina, in at least 2-3 differently colored layers plus the exposed pink of the underlying copper. The lettering, and the devices on the reverse (except the N) look very sharply defined, as do the legends on obverse. So they are unlikely to loose out on stripping. It's the bust that scares me, that red, pebbly patch on the cheek looks scabrous and might lead to some deep pits if the coin is stripped.

The idea of trying something else before nuking the coin is a good one. I never use olive oil, unlike the other poster, but that's worth a try. It literally can't hurt and only causes a little delay.

I might also try a wash of sodium hexametaphosphate, which might help clean up some of the very pale patina (which I presume is that directly on the copper surface which means the darker patches are on top of the lighter green). I use this in a 5% solution for short soaks (5-20 min) to try to loosen up grime and junk on very hard and dirty coins. At this concentration it is relatively safe for patina and won't etch any exposed metal. at 15% it will strip all patina, other corrosion products, and possibly etch the metal, which is not a good thing, though there are ways to lesson the risk of this.

I'll respond more tomorrow with more info on this tactic and a link to source material.

How would you strip the coin? Chemically or via electrolysis? If chemically, what substances do you use?

Mark


Offline Mark F

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Re: To strip, or not to strip, Sev Alex?
« Reply #3 on: September 11, 2020, 01:40:05 pm »
Ken,

Source material for my comments above are included in a PDF file from TAMU Marine Archaeology Dept at this location:

https://nautarch.tamu.edu/CRL/conservationmanual/cupreous.pdf

Note that this is a summary/extract from a much broader Conservation Manual, same department, at this location:

https://nautarch.tamu.edu/CRL/conservationmanual/File12.htm

I use the information within the first link routinely. NOTE that sodium hexametaphosphate is used sometimes in conservation to STRIP PATINA, so watch yourself. I use it at a 5% concentration (5g per 1L distilled water) and have never had a problem with it. I have never used a higher concentration to remove patina - if that is ever deemed necessary I use other methods.

Also, I do use BTA now on all my bronze coins as a final step before waxing and inserting them into flips and since I started that I have never had bronze disease on a treated coin. BD here in the desert is not a big thing, but I have lost coins to it before and several of them were heart breakers.

Final FYI. I purchased both chemicals from Amazon, less that $20 each in a quantity that will probably last me 20 years. Not sure where you live or what  the laws are, bit the hexametaphosphate is now used in very advanced cooking chemistry and is food safe.

Let me know if this helps.

Mark

Offline Ken W2

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Re: To strip, or not to strip, Sev Alex?
« Reply #4 on: September 14, 2020, 01:45:09 pm »

Thanks very much for the input guys.  I considered that simply waxing likely will bring out some detail and maybe even out the appearance some.  I now avoid using olive oil as in the past I have never been able to get it completely off/out of coins.

I have used electrolysis for stripping many times (and accidentally stripped a lot of 20 coins boiling in sodium sesquecarbonate once), but generally just use lye.  I've considered BTA for stripping and conservation (read that same Texas A&M article a few years ago when leaning how to conserve copper alloy Civil War artifacts), but never used it.

I have not stripped any coins in a few years, but will strip this coin in a batch of ten in the next few days.  I'll take some before photos and then take some at different stages to show the results.

Thanks again for your replies.

Ken   

   

 

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