ALERT The MDF has a monthly Prune of all Members that have Zero Posts to their Accounts to Free up Resources. However Just 1 Single Post will keep your account open indefinitely.

Straightening silver coins

Please post all your topics related to cleaning your metal detector finds here.
Post Reply
User avatar
thefiggis
Moderator
Posts: 6995
Joined: Sat Feb 18, 2017 8:19 am
Location: Norfolk
Has thanked: 1838 times
Been thanked: 2398 times

Straightening silver coins

Post by 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 ::g

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 ::g

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? :D

Low-quality/debased silver requires special care and attention before proceeding.
You do not have the required permissions to view the files attached to this post.
Essential equipment:
Some sort of electrical gubbins(I'm told it's a Deus). In various colours
Jenkins
Gin.

This topic has 29 replies

You must be a registered member and logged in to view the replies in this topic.


Register Login
 
Post Reply

Return to “Cleaning Finds Forum”