Removing grey rust from silver tanka

[Md. Shariful Islam]

I am not sure but guess that the rust on this is just a layer of cement. Looks ash. But inside it is a silver coin. Exposed portions of the coin makes it sure. How to clean this one?

[Md. Shariful Islam]

Probably it's not cement... I guess it's a thick layer of white color minerals or other... I tried to scratch with my nails but did not have any impact... So hard...Baking soda, ditergent did not work at all. What's next?

Islam

[Figleaf]

I like this recipe and the poster knows what he's talking about.

Peter

Silver coins can be cleaned with mild acids - ie lemon juice. One method is to put the silver coin in a wrapping of aluminum foil with baking soda, and placed in a dilute lemon juice/water combination. This is a simple form of "electrolysis" without a power supply.

[Prosit]

You realize that Baking soda is alkaline and pH + while Lemon juice is acidic and pH -.
When acidic and alkaline substances are mixed in molar equivalents they neutralize each other and form salt water of one sort or another.
If not equivalent molar amounts then the mixture can be either acidic or alkaline depending on which part is greater.

Salt water certainly will carry a current and with two dissimilar metals the potential for a micro current is possible and likely.

Why not just use salt water and the foil?

Dale

I like this recipe and the poster knows what he's talking about.

Peter

[Md. Shariful Islam]

For how long the coin should be sinking in the acid? As the coin will remain covered with alluminium foil and could not be seen its condition.

Islam

[Md. Shariful Islam]

Thanks to Bruce. I have finally cleaned this Gyath Al Din Bahadur AR Tanka. I had to be a bit harsh on it to remove tough rust. I put the coin in water mixed with baking soda for about 12 hours. Getting no significant result tried to use other techniques suggested by Bruce. I took about 250 ml mustered oil and mixed one teaspoon of white Vinegar and lemon juice in it. Added the coin in it and put the oil (in a metal bowl) on stove. Heated until the oil boils. Left the coin in the oil for 5 minutes.
I found that the coin has got rid of a few rusts but still there was thick rust on it and the letters and silver could not be seen. Then I decided to use harsh method. I took a bowel of hot water. Added a few baking soda. Put the coin on a alluminium foil. Left them for an hour. When I took the coin out I tried to remove the rust using my finger nail and found that the rust are breaking away. Then I took some toothpick, a piece of Daton (brush made of wood stick) and worked about an hour and cleaned using these tools. I tried to clean as much as possible. I concentrated on cleaning in such way that the letters and design could be exposed, not more than that.

The result is this.

Islam

[Figleaf]

I think you won, Tanka. There is additional detail around the edge now that could not be seen before. That's my personal benchmark for cleaning coins: does the coin show more or less detail afterwards? You have an attractive-looking coin now plus you acquired cleaning experience. Congratulations.

Peter

[Md. Shariful Islam]

Same feelings Peter. The additional detail that are visible now gave me satisfaction. Now I need the help of Oesho to read them. These Arabic alphabets without jer, jobor and pesh are difficult for me to explore.

Islam