Clean a drachm?

I see you know more chemistry then me, (but still, maybe less about coin cleaning?) EDTA became very popular specifically for treating Bronze disease, and I have some somewhere, but I heard it might be a carcinogen, so I never much used it.

I am pretty hesitant about giving advice on web groups about coin cleaning, as who know who will read it - and maybe not be careful about what they get up to?

Looks to me like the top drachm has already been incompetently cleaned, and left with specks of blue/purple/blackish silver chloride? Easy to remove - if so - by softening with Goddards silver dip and then soaking for just 15 or 30 minutes in ammonium thiosulphate. I think that is safeish to use (???) but.........caveat emptor

I got my grounding in coin cleaning from a guy who worked in the BM lab long ago.

But I heard he ended in hospital with kidney damage from the stuff he did.....

Rob T

PS I would leave the Syracuse tet alone. That sort of silver chloride will very likely leave a big corrosion hole if you take it off. But the drachm at the start might well be OK. Just guessing.

 

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I wouldn't say "maybe less" but, whithout any doubt, "most definitely much less".

I know about this debate, which at some point reached quite a media prominence and lead to a range of related studies. Here is a 2001 safety assessment by the CIR ("Cosmetic Ingredient Review"), here is the current WHO fact sheet on EDTA based on a similar study (summarized here). Both studies came to similar results, I quote: "EDTA does not appear to be teratogenic or carcinogenic in animals. The vast clinical experience of the use of EDTA in the treatment of metal poisoning has demonstrated its safety in humans" (from the WHO fact sheet). Whether and to what degree to trust such studies is everyone's personal decision, I assume, but I generally do.

That of course doesn't mean that the substance shouldn't be handled with great care, not swallowed, never left in reach of children, never used in a kitchen environment, etc. Thus, I do very well understand the general hesitancy you expressed, and will think of it should a similar topic come up here again.

(By the way, I don't know if this the right place to express how grateful I am for your 1995 "Jitals" catalogue which I used just yesterday, but I nonetheless want to do so...)

 

Many thanks - that's good enough for me too. I heard good things about EDTA for treating "Bronze Disease" about 20 years back, and went and got some - but the stuff I got came in kind of thin filaments, that looked like they would easily puff out an aerosol of sorts, so, being ignorant, I left it alone.

On the few old tricks I picked up before that - I think they are all in:

The Conservation of Antiquities and Works of Art. Treatment, Repair and Restoration. H. J. Plenderleith. OUP, London 1956

Regards

Rob T

 

Does anyone know or has tried something called Proargentol 351 for eliminating horn silver?

 

Sounds exotic. Only substance I’ve ever used is sodium thiosulfate and it works wonders at removing horn silver and, perhaps surprisingly, iron oxide deposits too!

 

For demonstration purposes, here’s just about the most extreme silver cleaning you’ll ever see:

after sodium hydroxide:

after sodium thiosulfate

as you can see, sodium hydroxide takes off all the hardcore stuff while thiosulfate is the targeted specialist that goes after the black horn silver and brown iron oxide.

don’t ask me why or how, I ain’t no chemist

 

Well done! The green are copper oxidations, which dissolve easily in weak acids (I always use synthetic citric acid). The black depositions are likely horn silver (AgCl), which dissolve in sodium thiosulphate.

well ...:

 

https://www.chema-shop.de/prestashop/product.php?id_product=128

 

Is it only available in Germany, or in the US under a different name?

Trying to find out if this is Sodium thiosulfate, but the chemical composition at the chema-shop website doesn't seem to be in the description