Author Topic: video of British Museum coin cleaning with chemicals  (Read 1681 times)

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Offline capnbirdseye

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video of British Museum coin cleaning with chemicals
« on: November 14, 2014, 04:58:55 PM »
This is the method I've been using, Sodium Hydroxide is more commonly known as Caustic Soda & used as a drain cleaner & used with caution can give remarkable results


http://www.dailymotion.com/video/x23sq12_cleaning-coins_lifestyle

Vic

Online Figleaf

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Re: video of British Museum coin cleaning with chemicals
« Reply #1 on: November 14, 2014, 05:43:27 PM »
Nice. If English is your second language, sodium is natrium and the stuff used is NaOH (natrium hydroxide - see the Wikipedia lemma), which should indeed be handled with great care. Some criminals used it to dissolve the bones of their victims...

Also, heed the warnings in the video that not all coins need to be cleaned this way and with this method you'll lose your coin if it's already too far gone.

Peter
An unidentified coin is a piece of metal. An identified coin is a piece of history.

Offline capnbirdseye

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Re: video of British Museum coin cleaning with chemicals
« Reply #2 on: November 14, 2014, 11:39:46 PM »
Here is an example of using similar treatment with just Sodium Hydroxide, it cleaned off the green mould but left the coins patina intact & in doing so exposed an almost unique coin
Vic

Offline bruce61813

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Re: video of British Museum coin cleaning with chemicals
« Reply #3 on: May 14, 2015, 05:50:24 AM »
Sodium Hydroxide is commercially known as Lye and has a very high pH, well above 12. The dry crystals will cause severe burns if you get them on your skin.  It can be mixed with sodium carbonate & sodium bi-carbonate as a soak for hard clay encrustations.  It will break down organic materials that hold clay particles together, and will dissolve copper oxides. The browning of the surface copper is typical.  A further note, never dissolve the powdered form in hot water, it will turn the water to steam and will splatter. Always us cool water .

Bruce

Offline Arminius

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Re: video of British Museum coin cleaning with chemicals
« Reply #4 on: May 14, 2015, 10:28:33 AM »
Cleaning is never the same and the BM video probably does not show all essential details we should know.

Sodium hydroxide solutions can be concentrated or diluted, in pure water or with additional solvents, hot or cold, new or old (and so completely converted to sodium carbonates).
Coins may be treated before, short or long times, with or without further surface treatment, ...

So it´s more or less speculation discussing treatment experiences "with chemicals" but without all details.

Offline bruce61813

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Re: video of British Museum coin cleaning with chemicals
« Reply #5 on: May 15, 2015, 11:10:03 PM »
What I was trying to point out is that in the dry, crystalline form NaOH is very exothermic, a tablespoon in a pint of water will raise the temperature to over 120 degrees F from a 80 deg F start.  Adding the  crystals to very hot water cause stem to form and splatter the liquid.  Once the NaOH is dissolved, you may heat the solution, also use non-metallic pans or beakers.

Bruce