Olive oil and nickel-brass threepences - advice please

[Stuntman 264]

After searching on here in regard to conserving/improving coins, I've been immersing a few of my relatively low value silver and bronze coins in olive oil. All such coins have shown improvement after 2 weeks immersion followed by a rinse in de-ionised water. The best results have been on 1920-1946 silver where there had previously been light, green (verd?) deposits. I've tried it on two coins with much more entrenched green deposits and these have both improved to a decent degree as well after 3 weeks immersion.

I have also just immersed 3 George V farthings in olive oil and again, this has done the trick in removing heavier (but still not too bad) traces of green deposits after two weeks immersion and some light prodding with a softened and blunted cocktail stick.

So I'm now experimenting on two nickel-brass threepences from 1943 and 1954. These are F to GF grade (came from family members 35+ years ago) and they don't have any green deposits but they do have a brownish colour to them which appears to be a deposit or similar, rather than just wear and toning.

The reason I'm asking for advice is because I have a 1946 and a 1949 threepence, both of which I also picked up about 35 years ago in the rummage box of a coin shop for something like 50p each. The 1946 is perhaps GF+ or NVF if you're being generous, the 1949 is F to GF. Both coins have a bit of this brownish colour/deposit to them and ideally I'd like to improve them a bit.

So - any tips for conserving/improving nickel-brass coins if olive oil doesn't make a difference?

Thanks in advance!

[VickySilver 923]

Nice solvent/acid there. However, olive oil is not water soluble and will have to remove residual with detergent of some ilk - I use the dish detergents we have on this side of the pond.

The residue if washed in any sort of water will continue to react with the surface of the coin, and copper alloy will start to go a bit pinkish.

0.500 silver seems to attract chloride oxidants, almost regardless of the alloy. This would include PVC, but also other chloride/chlorite oxidants. These in turn can be removed by the acid quotient of olive oil as well as the compounding agent by the solvent action of the oil. Likewise it is useful in other brass & copper bits as well, much as your reported experiments support.

So olive oil has a virtual family of organic compounds in it that make it up, including both polar (water soluble and acid components) and non-polar (hydrocarbon chain components). Sorry to harp on this bit.

My recommendation: continue to experiment with exposure times, etc. but that after each "treatment" to please remove the residual oil as stated. I always tamp dry with high nap white cotton toweling.

PM me if you'd like...

[Stuntman 264]

Cheers Vicky ​

I do dry the coins afterwards using kitchen towelling paper rather than high quality cotton towelling.

Should I go back and use detergent on the coins that I have previously immersed and then rinsed in de-ionised water? I was under the impression that leaving a thin film of olive oil on the coins would do no harm, but I'm very happy to be corrected.

[VickySilver 923]

By all means yes. As I've said the residual olive oils can act on the metal surface (acidic components) . Mineral oil will be much less active to nearly inert....

[copper123 1,611]

The old favorite acetone may be better , its great on copper and bronze so I see no good reason why brass 3D'S would not be improved

[Stuntman 264]

Thanks copper123.

How long should the coin stay in the acetone, as a general rule of thumb?

And where can I buy acetone - is it easy to find on the high street or do you need to go somewhere a bit more specialist?

I'll experiment on another family-sourced nickel-brass threepence...

[Stuntman 264]

I've just been reading hazelman's thread "Using acetone to clean coins" which answers my questions above!

[copper123 1,611]

Coins mostly need a quick wipe with just toilet paper soaked with acetone or a cloth , a cloth is better but you also have to wash it because acetone is a smelly solvent that you really don't want to be handleing , ever .

This removes all the gunk from coins , you know the stuff that gets transfered from years of being handled in peoples pockets , removes all the grease and dirt and give the underneath a chance to shine through again

Soap and water also works as well but just not as fast , several washes might be needed .

Remember NEVER rub to hard or the coin might end up with surface scratches

[VickySilver 923]

Even fresh Toilet paper (LOL) has a lot of ugly compounds, mainly sulfur derived that may possibly layer out on coin surface. Please wait until you get that clean white cotton high nap cloth!

Edited October 16, 2015 by VickySilver

[PWA 1967 2,444]

The lint free cloths on amazon are only a couple of pound and spot on.

[Stuntman 264]

Cheers chaps. I'll continue to experiment, wash and dry accordingly!

[Stuntman 264]

Update: after 8 days of immersion in olive oil plus some light prodding with the softened and blunted cocktail stick, there has been a significant reduction in the amount of brownish deposits on the two threepences, but I think the general eye appeal might be a little worse.

This is because there are now a few patches of lighter colour (being the underlying alloy colouration, I think) which makes it look as if the coins have been cleaned/scraped a bit. I don't think I've done that with the cocktail stick.

The George VI coin seemed to get a bit darker in overall tone (which made it look worse to me), whereas the Elizabeth II coin seemed not to change in overall tone.

So overall, I don't see it as an improvement so I'm not going to do a similar thing with my 1946 and 1949 coins. I might just give these a gentle wash with detergent and de-ionised water and then carefully pat dry. They're nice enough as they are: fairly good honest coins.

[VickySilver 923]

Hmmm, yes we did forget to mention that bit. Not called pot-metal for anything though, this alloy is total junk as far as collectors. I have a number of VIP proofs that don't look too bad, but let there be a fingerprint (or worse).

However this is true even of silver - remove the oxidation and crud and no telling what you get as sometimes the "crud" is protecting the underlying metal a bit and then you have residual variegate toning.