Help in diagnosing corrosion? BD on ancient silver?

Showmetheway

Hello folks,
pulled out this purchase from two years back and I'm concerned on what to do. Coin is a Durotriges stater (presumably billon, though XRF-tested as 76% Ag) and has been sealed in an airtite since purchasing it. Comparisons to seller's photos is consistent with the amount of green stuff on it as today so it doesn't seem to be spreading in a vacuum like BD, and its texture can be described as a light-green "moss" filled in every crevice on the coin, particularly the reverse side. Any help would be appreciated!

Seller photo:

Current state:

Sorry for crappy photo quality... I'm trying to my improve coin shots slowly

bronzemat

Still looks like bronze disease. I had a tetradrachm with very low silver just recently & the usual distilled water soak and some scrapping with a toothpick and more soaking, now it's BD free.

amwldcoin

That looks more like a rock than a coin!

Showmetheway

@bronzemat said:
Still looks like bronze disease. I had a tetradrachm with very low silver just recently & the usual distilled water soak and some scrapping with a toothpick and more soaking, now it's BD free.

Interesting... Curious what the threshold of copper/base metal content is required for BD to take hold. I've yet to have heard of 40% half dollars forming severe if any BD. Did you ever end up 'baking' the coin to dry out leftover moisture?

@amwldcoin said:
That looks more like a rock than a coin!

Lol it's like a little moon, part of the reason it's been kept 🌙

bronzemat

@Showmetheway said:

@bronzemat said:
Still looks like bronze disease. I had a tetradrachm with very low silver just recently & the usual distilled water soak and some scrapping with a toothpick and more soaking, now it's BD free.

Interesting... Curious what the threshold of copper/base metal content is required for BD to take hold. I've yet to have heard of 40% half dollars forming severe if any BD. Did you ever end up 'baking' the coin to dry out leftover moisture?

@amwldcoin said:
That looks more like a rock than a coin!

Lol it's like a little moon, part of the reason it's been kept 🌙

On some junkers, darkened the coins despite following directions from advanced collectors at the time. Never done it again.

As for the 40% halves, you have to remember ancient coins have many other trace amounts of junk metal in them not counting whatever soil conditions they were buried in for thousands of years.

Showmetheway

Ahh that's what I feared, especially with inconsistent mixtures like the drachm, I don't want the coin to crisp...
Ancients are just wild like that I suppose

amwldcoin

Agree!

@Showmetheway said:

@bronzemat said:
Still looks like bronze disease. I had a tetradrachm with very low silver just recently & the usual distilled water soak and some scrapping with a toothpick and more soaking, now it's BD free.

Interesting... Curious what the threshold of copper/base metal content is required for BD to take hold. I've yet to have heard of 40% half dollars forming severe if any BD. Did you ever end up 'baking' the coin to dry out leftover moisture?

@amwldcoin said:
That looks more like a rock than a coin!

Lol it's like a little moon, part of the reason it's been kept 🌙

7Jaguars

Simple electrolysis would probably do it if 76% silver content. That is the heated vinegar with the aluminum foil and the baking soda trick....