My First Soak. Thoughts?

Since you removed the thin dirt patina which was on top of both the bare medal and the gunk, the contrast between the two now looks more prominent.
How long did you soak? I would leave it soaked for like a day on several runs.

Keep in mind that oxidation won't be removed by either water or acetone (and that is why we like both!). You need to observe the surface under some magnification to see whats going on and the difference between soaks.

Since this is an inconsequential coin, I would also advise to try soaking a qtip and work the surface very gently after a soak, just to teach yourself what happens; patting or then gently rotating the tip. This is obviously not good for coins you want to restore in mint state but it's a valuable learning experience to try to distinguish gunk vs oxidation or to give you reasonable expectations on what soaks will remove.

Hope this helps

You have to attack different conservation problems from specified angles. This may be outside the realm of acetone and into the realm of naphtha. Either are acceptable but do different things. Same with MS70. Also; for cases of organic encrustations, long acetone soaks are required. You'll need a lidded glass jar (not plastic) since acetone evaporates very quickly.

If the surface of an aluminium-bronze coin has turned black and bubbly, that's almost certainly due to corrosion, rather than "gunk". So I strongly suspect that any simple solvent soak is going to be ineffective.

I would presume this coin to be a "ground find", by metal detector or some other means.

In terms of "the coin looks worse after a water soak", what has probably happened is that the "dirt", or corrosion, had dried out over recent decades, and has now been thoroughly re-hydrated by its water soak. I would equally suspect that if you placed it in a cool oven (80 to 100 deg C) for an hour or so, the paler colour would reappear as the crust dries back out again.


As a chemist, the difference between "soaking a coin in a solvent" and "soaking a coin in something that will cause a chemical reaction" is obvious to me, but I can understand that such processes can seem very similar to the uninitiated: "coin goes into liquid, comes out of liquid maybe looking different". This is why the general advice for new collectors is always "don't clean coins".

Solvents remove "foreign matter" - this is when something that is not-coin has attached itself somehow tot he surface of a coin, but has not actually reacted chemically with it - all of the metal that was part of the coin is still there, underneath the dirt. This is simply washed off by the solvent, leaving the coin unreacted and unaffected.

Acids, alkalis and chelating agents remove "corrosion byproducts". In this case, a foreign substance has attached itself to the coin as before, but there has now been a chemical reaction between the substance and the coin, such that the "goo" is now a mixture of atoms originally from the coin and atoms from the goo. This is usually not removable by solvents, since it is chemically bonded with the coin's surface. The chemical reagent can attack, dissolve and remove the corrosion, but some of the original metal will be dissolved too. Such chemicals also usually attack the toning/tarnish/oxidation.patina on the coin's surface, since toning/tarnish/oxidation/patina are just fancy words for different forms of corrosion - only those forms of corrosion are wanted, because collectors think they look nice. If used carelessly, such chemical agents will remove ALL of the corrosion, including the bits of corrosion we might have wanted to keep; the result is a "stripped" coin that looks unnaturally clean.

Awesome guidelines Sap!

I'll also add for lahave56 to remember that temperature will also increase the effectiveness of the solvent so when I do these kind of things I usually try to place the soaks near a radiator or a warm place.
Conversely doing it outside in the winter will probably be not a great idea.

Obviously beware of acetone which you want to keep outside, so if you place it inside the house (and in a warm place nonetheless) then make sure that the container is sealed properly.

Very interesting experiment. Thank you for sharing with us. If it matters, the cameo look is somewhat appealing to me.

You can type [q] and [/q] out manually.


My pleasure.