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Over Pickled.

Updated: Mar 1

This came up in a class recently and has been a question a few students have asked over the years. Can you over pickle your silver by leaving it in the acid too long? Absolutely.


Pickle is what we use to clean the copper oxides from the surface of metal when it's been heated or soldered. It usually a solution of acid and water or sodium bisulphate and water. It's used to clean all the precious metals we work with in the workshop but here we will focus on sterling silver which is and alloy of 92.5% siler and 7.5% copper.


If you need some advice or help with choosing, using or disposing of your pickle read our 'In A Pickle' post here https://www.nottinghamjewelleryschool.co.uk/post/in-a-pickle


HOW DOES PICKLE WORK?

The acid molecules in the pickle bond with the copper oxide molecules in the silver and lift them out of the metal. If you notice your pickle going green or blue over time, this is the acid slowly filling with the copper oxides.


HOW LONG SHOULD YOU PICKLE FOR?

The time a piece needs in the pickle varies depending on the type and strength of the pickle, the temperature of the pickle, the size of the piece and the amount of oxides on it's surface. Essentially your leave your work in there until the surface is bright and oxide free. Properly pickled silver is a white colour. This could be from 5 mins for hot, fresh pickle, to a couple of hours for a cold solution.


WHAT DOES OVER PICKLED SILVER LOOK LIKE?

If your silver is in the pickle pot too long it can become over pickled. The acid begins to eat further into the surface on the silver leaving it looking very matte and roughened. It will also start to discolour and look brown, grey or black depending on how over pickled it is. Over pickled silver can look a lot like underpickled silver.

If your silver is drastically over pickled - i.e you forget it and leave it for hours or days or weeks, check any solder joins. The acid will eat through the solder faster than the silver and can severely weaken the joins.


HOW CAN I PREVENT IT?

To avoid over pickling make sure that your pickle isn't too old and mucky, too strong or too hot.


If there is sediment in the bottom of the pickle pot or if the solution is a very strong blue colour it might be time to change your solution. See our guide to ethical pickle disposal here .


To make sure your solution isn't too strong, use approximately a tablespoon of citric acid to a litre of water and use the solution warm.


Keep the solution warm but not hot. It shouldn't be bubbling or steaming. If you are using a slow cooker, set it to warm or medium and not to hot.


HOW CAN I FIX IT?

If you do over pickle a piece then don't panic. You can save it.


Take it out of the pickle and rinse and dry the piece. If it is a flat piece or simple construction, you can use a fine emery or abrasive to sand away the over pickled surface and reveal the clean metal underneath.


If the piece isn't an easy shape to abrade you can burn the acid away. Put it on your soldering block and wave a soft flame over the piece. You need to get it hot but not hot enough to melt any solder. If the piece is over pickled then you will see a green flame flickering around your silver. Heat until oxidised and then re-pickle and remove as soon as the oxides are removed (don't leave it in too long). You may need to repeat a couple of times until your silver looks nice and white.


Once you have burned away the discoloration and re-pickled. It should look fresh and clean and ready for your next stage.




When mixing or using your pickle wear eye protection, an apron and take care to not splash or spill the solution. Rinse up any spills quickly with plenty of fresh water.




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