Ultrasonic cleaner for Bronze Disease?

"A true 5% by weight solution of sodium sesquicarbonate in water is what should be used for bronze disease treatment. This is the solution that has been investigated by the British Museum and found to be effective and safe."

https://www.accla.org/actaaccla/bronzediseasetherapy.html

 

Log in or Sign up to hide this ad.

If the interior of the Ultrasonic cleaner is ALL plastic , probably OK. If metal basket or interior, it might leave microscopic marks. Jim

 

Hoi,

Is this method also applicable to AE - and copper coins from the 3rd - 5th century?

Thanks, sky92880

 

I would be careful using an ultrasonic cleaner. As pointed out, damage to surface could occur.

Dealing with bronze disease is basically a chemical neutralizing process, removing the acidity that is driving the BD. I don't think there is any shortcut to this process, and depending on the extent of the BD, the process might take weeks, even months. Patience is the order of business here.

 

I apologize as I am sure this has been covered however... what is sodium sesquicarbonate? is it Borax? and can a person just walk into pharmacy or grocery store and find it? Then dilute to 5% with water and soak the coin?

 

Sodium sesquicarbonate is a weak base, like sodium carbonate. You want a weak base so the reaction occurs slowly over time and doesn't "burn" the coin. I don't think sodium sesquicarbonate is readily available in grocery stores or pharmacies but you can buy it on E-Bay or online chemical retail outlets. It is present as an ingredient in some products you can find in grocery stores though, so not hazardous.

The other alternative is benzotriazole, which the museums often use, but it's a known carcinogen and is very difficult to handle. I've stuck with sodium sesquicarbonate and have been able to neutralize bronze disease on several coins I've diagnosed it in. Like @robinjojo says, it is a long process, with repeated treatment, taking weeks or even months, but it's worth it in the end.

 

It's different. It's sort of like a mixture of sodium carbonate ("washing soda") and sodium bicarbonate ("baking soda"). It's unlikely to be in a random pharmacy or grocery store, but it's on Amazon (and presumably eBay).

Once you have it, yes, just dissolve one part of it in 19 parts (by weight) of water.

 

You may want to start with a lower concentration. In my experience, 5% will essentially strip the patina and leave a bit of a rough surface. You also have to be careful that the water doesn't evaporate too much over the days/weeks you leave the mixture as that will increase the concentration. Change the solution every few days at the start when it turns blue, eventually you'll only need to do it once a week or so.

 

Thanks for your reply.
I think i start at 2.5% on a coin with mild traces, and see what happens.