Cleaning Coins

[Geordie582]

I bought a little book today, from a charity shop, that has proved very informative - but has to be taken with a pinch of salt in places!

It is a 1970 issue of "Teach yourself Numismatics" by C.C. Chamberlain.

One pearl of wisdom I thought I'd pass on:-

"Cleaning Coins. Where a copper coin has a fine patina or a silver coin is richly 'toned', they are best left alone. A badly corroded coin, however, can be improved by brushing with sawdust soaked in diluted sulphuric or citric acid. Ammonia will remove green oxide."

So now you know!

[Peckris]

There's been a subtle change I've noticed in recent years, in relation to cleaning. I was at an auction where there was a group of high grade George V last issue silver 3d. Yet many of them had been obviously cleaned to look even brighter than they actually were. I was reluctant to bid until I spoke with a fellow dealer who said "Sure, they've been cleaned. But there are lots of collectors around these days who just don't care." I was sceptical until I remembered that I had picked up a huge auction lot previously, where most of the coins had been cleaned including a large number of George V shillings in EF or better - 1912, 1917, 1919, among them. I always advertised them as 'cleaned', and adjusted the price accordingly. I had no shortage of buyers.

It does seem as if (maybe younger?) collectors are becoming more relaxed about cleaned coins - this is probably stimulated by a shortage of high grade pre-1937 coins in relation to demand.

[£400 for a Penny ?]

Have you contracted Verdigris overnight, or is that Envy - an original sin I believe ?

I think a lot of people cut their teeth in coins of this period, it is after all easier to understand what is going on. I believe in time, those cleaned coins will surely be passed on ?

[Peckris]

Have you contracted Verdigris overnight, or is that Envy - an original sin I believe ?

I think a lot of people cut their teeth in coins of this period, it is after all easier to understand what is going on. I believe in time, those cleaned coins will surely be passed on ?

Hahaha - no, it was just the colour that seemed to best show up the detail (when we're limited to a paltry 100 pixels square, what can you do? )

I can tell you - and this is personal experience only, don't try this at home kids! - that I've dipped silver, I've treated verdigris in a weak vinegar solution overnight, I've removed 'film' from bronze with methylated spirits, I've washed silver in warm soapy water. Some of those worked better than others, but I have rarely ever damaged a coin by cleaning. The worst thing that happened was when I dipped a lustrous George III VF halfcrown that had a few black spots in the legend. Turned out the 'spots' were some kind of horrid tar-like substance and the halfcrown went a kind of uniform smeared grey and never recovered. But in general, I've been ok so far.

Bottom line : it's up to an individual whether to try any technique or leave well alone. Judging by the number of cleaned coins on eBay, I'd say we are in an epidemic of frantic polishers.

[1949threepence]

Since a sobering experience with a virtually UNC but dirty 1881H halfpenny (which I may have mentioned in another thread), I have never ever cleaned another coin. Nor would I buy one that I thought had been cleaned. I can nearly always tell when they have been cleaned as well, and it is very easy to distinguish cleaning from lustre, even on a photo.

I'd rather have a coin with a few dirty marks or a stain, than a cleaned and consequently, slightly unnatural looking coin.

Edited August 15, 2009 by 1949threepence

[VickySilver]

Well, what about cases where there is just residual dirt adhering to the surface - would you not clean with mild soap and water at least?

I too have a bit of experience and can tell you that copper must be approached with temerity, although mild treatments can be tried. I suggest if you have the time or inclination that you experiment with bits of lesser to no value to see how metal reacts in certain circumstances.

A few "pearls":

no abrasives

no copper magic or other acid dips

acetone which is pure should be safe

tamping, as opposed to rubbing surface with clean white cotton towel is good way for removal of excess solvent

always wash thoroughly with water and then tamp down as the water itself may have harmful electolytes

Well, more if you ask.

[Peckris]

Well, what about cases where there is just residual dirt adhering to the surface - would you not clean with mild soap and water at least?

I too have a bit of experience and can tell you that copper must be approached with temerity, although mild treatments can be tried. I suggest if you have the time or inclination that you experiment with bits of lesser to no value to see how metal reacts in certain circumstances.

A few "pearls":

no abrasives

no copper magic or other acid dips

acetone which is pure should be safe

tamping, as opposed to rubbing surface with clean white cotton towel is good way for removal of excess solvent

always wash thoroughly with water and then tamp down as the water itself may have harmful electolytes

Well, more if you ask.

I've always found a cotton bud dipped in surgical spirit good for dirty or filmed copper / bronze, while soap and water does the same for silver. Drying requires patting with a clean dry towel, or wiping lightly with a micro cloth (the sort you clean specs with).

[VickySilver]

I think in the US, the cotton buds are referred to as Q-tips and some can be quite hard so be careful with friction on these. Presoaking the tip gets them a bit softer but if you've the inclination to rub out that persistant spot, you'd best not. Some spots are just going to be resistant to all but the most aggressive agents but then they leave their mark.

[1949threepence]

Well, what about cases where there is just residual dirt adhering to the surface - would you not clean with mild soap and water at least?

I too have a bit of experience and can tell you that copper must be approached with temerity, although mild treatments can be tried. I suggest if you have the time or inclination that you experiment with bits of lesser to no value to see how metal reacts in certain circumstances.

A few "pearls":

no abrasives

no copper magic or other acid dips

acetone which is pure should be safe

tamping, as opposed to rubbing surface with clean white cotton towel is good way for removal of excess solvent

always wash thoroughly with water and then tamp down as the water itself may have harmful electolytes

Well, more if you ask.

Yes, any obvious residual easy to remove dirt, I'd do with a damp cloth with no soap, and then dry with an anti static cloth.

I should have mentioned that as technically it is cleaning, but to be fair, that's not what I class as true "cleaning", as it doesn't involve any radical measures.