Straightening silver coins

[thefiggis]

As with many aspects of cleaning or "improving" coins, the subject of straightening a bent one has many opinions ranging from "never!" to "of course, why not?". The primary concern, rightly, is for the coin itself and its value both personally and to the pocket. Make no mistake - if not straightened professionally then you will lower if not destroy its monetary value, but if on the other hand it's never to leave your collection and/or is of little value then it's something you might want to consider trying.

Personally, I never hesitate in straightening coins as I never intend to sell them. My straightening processes run from cold pressing to the full-blown annealing process described below - it all depends on the coin and its condition and careful assessment is needed before proceeding. Anyway, on with the motley...

Disclaimer: the method described below works for me but anyone who takes on the straightening of their coins does so at their own risk and any damage to coin value, self, pets, property or neighbours is entirely their own responsibility.

This little fellah was in a bad state - bent right over and with a nasty split - and annealing was the only answer.

mullered hannered.jpg

Stage 1
Equipment used: old saucepan upturned in a bowl of water, kitchen blowtorch, wooden spoon, wooden chopping board.

Place the coin on the base of the upturned saucepan, heat it with the blowtorch until dark red and then flick it into the water to quench (some say you should let the coin cool naturally but I've never experienced any problem using the water method). Place the coin on the chopping board and gently ease out a couple of millimetres of the bend with the spoon (or other wooden or non-abrasive implement).

Repeat this process until the coin is flat. I find a wooden spoon ideal for the process, with the round handle good for teasing out gentle bends and to act as a kind of rolling pin to finish it off.

When satisfied, give the coin a final annealing then cool.

This is what the coin looked like after this stage:

After annealing.jpg

Yes, it's flat, but...bit red, innit? Looks awful, in fact, and one of the problems with annealing is that the copper content of the silver rises to the surface. It can be counteracted by "pickling" but this process involves the use of nasty chemicals, none of which are for me, so I try to reduce the effect as descibed below.

Note: sometimes there will be virtually no reddening at all and other times the coin will blush like it's been told a really filthy joke - it depends largely on the purity of the silver.

Stage 2
Materials used: bicarbonate of soda paste

To help remove the red/reddy-grey/grey patination, you can use such as lemon juice or water & foil, but I like the bicarb paste as it's gentle and you have full control and can see what's happening at all times.

Make a thick-ish paste of bicarb and water and rub it gently over the coin until clean (or as clean as you can get it).

After rubbing with bicarb paste:

after bicarb.jpg

Still a little pink and of course we've lost the original patina but ,we can bring that back to an extent though it's not likely to match the original.

Stage 3
Materials used: bleach and a pencil rubber

Dilute one part bleach to two parts water and soak the coin until it turns black. Then rub the pencil rubber over it to expose the silver in the high spots. You can use an ink rubber but I find a pencil rubber more effective, albeit slower. If you decide you've overdone it and it's too bright then pop it back in the bleach and repeat the process.

If you don't like the idea of using bleach, try sticking the coin in a hard-boiled egg. It might take a little longer to darken the coin but you have a handy snack afterwards

The final stage is to soak the coin for a few hours in de-ionised water to remove any chemical residue.

Finished result:

after bleach.jpg

It still has a slight tinge of red which looks more pronounced in the image than in reality. Honest.

I'm happy-ish with the result, though there are a few tweaks still to be done on it, but overall it's a vast improvement on what it was.

Footnote: The use of boiling water in coin-straightening is pointless. It simply doesn't raise the temperature anywhere near that required for the annealing of silver and if you've used boiling water "successfully" then you might as well have saved yourself the bother and cold-pressed the coin in the first place. That's not my opinion - it's science.

Hope this has been of help and if anyone has suggestions to improve this method then please do shout and let's see if between us we can get this process nailed

EDIT:

Some great advice in the comments below which are well worth a read. They include:

Annealing should be done in low light to better see when the coin is at the correct temperature

Use various-sized rollers to ease out the bend

Re-patination can be achieved by placing the coin in a box full of rubber bands. Who knew?

Low-quality/debased silver requires special care and attention before proceeding.

[Ten pence!]

Pretty much what I do! As for the final flattening I place the coin between two bits of card from something like a cornflake packet, place the card and coin sandwich on a hard flat surface and whack it with a wooden mallet!

[thefiggis]

Sounds like a plan

Probably theraputic as well, though possibly inadvisable after a row with the other half unless you want a coin twice the diameter but half the thickness

Edit: thanks for adding the images, 10p. Great job

[alloverover]

it all depends on the coin and its condition and careful assessment is needed before proceeding.

This is the key, this is the secret, to success

[Ten pence!]

We never row!

You know when the coin is flat because the image appears weakly on the outside of the cardboard.

[Oxgirl36]

Didn’t know about the egg thing - cool

Great, detailed description Mr Figgis which will be very helpful for lots of people thank you.

[thefiggis]

it all depends on the coin and its condition and careful assessment is needed before proceeding.

This is the key, this is the secret, to success

Absolutely. I spend ages looking for hairline cracks or potentially weak areas before doing anything.

Another thing I've discovered is that I can take more liberties with Henry III coins than, say, the Edwards. They seem to be far more robust.

[sweepstick47]

Didn’t know about the egg thing - cool

Great, detailed description Mr Figgis which will be very helpful for lots of people thank you.

Boiled eggs are rich in sulphur content which is why the 'blackening' effect occurs. The same result can be achieved by generously 'dusting' (the coin) with powdered sulphur and leaving for a couple of hours and then lightly polish the highlights.

Whichever came first, neither a chicken or egg would be affected as a result

[sweepstick47]

Nice one Mr Figgis An easy to follow set of instructions with a well presented coin being the end result. That's got to be well deserving of a gin or three ss47

[thefiggis]

Had them, SS. Just before breakfast, in fact.

On the Mouton Rothschild now

[thefiggis]

Oooh, lots of lovely info there, PF

i anneal it twice before flattening

Be great to hear why you do it twice, please? Could well be a vital bit of info.

The pink effect that sometimes happens is easily removed by just rubbing the coin in the fingers with autosol metal polish .

There speaks a true vehicle paint lover

I don’t fake the patina back on the coin, time does it’s job perfectly

Yes, I've heard this somewhere before. But how long, would you say?

[Ten pence!]

How long? About 250 years seems to do it, as long as the coin is buried of course.
Bleach in certainly quicker though.

[Fusion]

I've plenty of successful experience of coin straightening, so thought I'd add a few comments:

I think 'cherry red' is too hot, that would be more appropriate for bronze/brass. A dull red is best for silver, which means you would need to perform the annealing in dull lighting -- bright daylight is going to make judging the red-ness hard.

Make each corrective bend modest, especially the first few. It's far better to make 8 or 10 repetitions than 4, there's more likelihood of visible cracks remaining when finished, if you're too hasty.

I prefer to clean the coin with a weak acid soak & brushing regularly with a soft brush before annealing. This will shift residual dirt/grit, and patches of green copper salts ( verdigris ), without doing anything to the coin ( unless it's a debased example ).

Re:" My straightening process .... depends on the coin and its' condition and careful assessment is needed"
You need to go into plenty of detail here - beginners have no ability to make this assessment.
My thoughts:
The older the coin is, the more important annealing is : a slightly rippled Elizabeth I may tolerate cold pressing ... a slightly rippled Ethelred could snap into 4 pieces as soon as you apply any pressure to it.
The more valuable the coin is, the more important annealing becomes - don't destroy a £1000 coin with unskilled technique.
Poor quality ( debased ) silver coins are more fragile, example Edward 6th, Henry 8th, they definitely need annealing, and even that could be too risky, and it's best to use prudence and leave them bent.
If there's any sign of cracking, annealing is essential, otherwise the crack will worsen.
Thicker coins, like groats, sixpences, are more prone to surface cracking, so they should be annealed. And they should be held at the 'dull red' temperature for longer than thin coins, to allow for more thorough annealing.

[thefiggis]

Thanks for that, Fusion. I'll incorporate extra info later

And you're right, PF - each to their own, as ever

[pasttarg]

a box full of rubber bands darkens silver coins in a few weeks