Numismatic and History Discussions > Uncleaned Ancient Coin Discussion

Treating rust looking breaks in patina

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Ron C2:

--- Quote from: Ken W2 on July 19, 2021, 06:55:46 pm ---
Thanks fellows.

Shawn, I assumed it was not iron related rust-- while there probably is some trace iron in the alloy it's likely not enough to cause real rust to this extent.  But, if I knocked a little of the green layer off either coin there would be this rust colored layer beneath it too. (That's how these spots grew from smaller ones initially).  It's like there is a layer of corrosion underlying the green layer.  I think I'll try a soak in a 5% sodium sesquicarbonate on the VRBS ROMA and just see what happens-- I'd like it to be darker and not rust looking.  I don't think that will do any harm, and if it does it won't be any great loss. Thanks again.

Ken

--- End quote ---

Ken,

The color is basically raw bronze powder and flake that has come loose from the fabric of the coin because of the spalling effect the green patina had on the coin itself when it formed. In essence, a chemical reaction is forming malachite mineral on the coin's surface and dissolving some of the bronze in the process.  This is why if you treat a patinated coin with diluted lye to remove the patina, the underlying flan is more porous than a smooth green patina.

Anything that darkens those exposed bronze areas will risk removing more patina, in my view. If you wax the coin, they will slightly darken anyhow. Personally, I would accept the coins as they are. Other work is likely to not improve them, but YMMV.

Virgil H:
I am no expert, but, seems to me that coins I have that have these kinds of issues would just get worse if I tried to get them off. Unless I am not seeing your images properly, these areas already have outer layers removed and in fact what the "rust" is is already gone. Unless there is a reason, I just leave this stuff as trying to take it off makes matters worse. I personally have never used wax, but maybe that would make it look better. I like coins as they are, though, to me wax is an unnatural manipulation that I don't want.

Virgil

Ken W2:

Just to follow up, I treated the VRBS ROMA coin with sodium sesquicarbonate soak over the week end. Didn't help or hurt.  I'll just dry in my usual fashion-- overnight alcohol soak, then a warm oven, then wax.   

Ken

Ryan B:

--- Quote from: Ken W2 on July 18, 2021, 09:55:34 am ---
..live with it and let it darken naturally or touch it up with Jax or LOS— depending on the camp you’re in.=

--- End quote ---

I'm familiar with Jax products, but what is LOS that was mentioned?

Ron C2:

--- Quote from: Ryan B on January 16, 2022, 05:50:06 pm ---
--- Quote from: Ken W2 on July 18, 2021, 09:55:34 am ---
..live with it and let it darken naturally or touch it up with Jax or LOS— depending on the camp you’re in.=

--- End quote ---

I'm familiar with Jax products, but what is LOS that was mentioned?

--- End quote ---

LOS is Liver of Sulfur.  It's used by some to artificially patinate some kinds of coins - often silver coins where you want a tarnished look.  The opinions on the advisability of doing so vary.  My personal view is that re-patinating a coin with chemicals that short-circuit natural environment patination crosses a line I am unwilling to cross myself.

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