Jump to content

Horn Silver Treatment on Eukratides Tetradrachm


Cordoba

Recommended Posts

I had bought a eukratides tetradrachm from roma a year ago, and it had a case of horn silver. It had progressively darkened, and got quite distracting, so I tried out sodium thiosulfate on it. It worked quite well, especially on the obverse. I have to thank Roerbakmix and his thread on cointalk detailing the process. The process was pretty simple, and I wasn't exactly scientific in measuring. I heated up distilled water, and made a solution of roughly 95% water to 5% sodium thiosulfate. The sodium thiosulfate would cause the horn silver to darken, and would come off afterwards in water. Below is the progression of the coin and then the after photos from cleaning.

Feel free to post any coins you've had luck cleaning, or bactrians 🙂

Several months after purchase

image.png.f4c777a1a78cc407162ab31dcfdaf1a9.png

Right before cleaning

image.png.54775048c06887dfa9715d37ab507c6c.png

After cleaning

image.png.a8b4ce955a5785a167b48f1eb655652b.png

 

Edited by Cordoba
  • Like 13
  • Clap 3
Link to comment
Share on other sites

Nice job! Interesting to see how much the horn silver darkened before you cleaned it. 

I see that after cleaning the coin has a yellow-ish dull tone to it. That often happens when cleaning with thiosulfates. In my experience it seems to prevent proper toning and can also give the coin an unnatural colour so I try to remove it. I haven't yet found a chemical method that removes it though. It can be removed by friction (e.g. using a small eraser), which won't polish the coin provided you don't do it a lot but it'd still be nice to find a better way of removing it than this. 

  • Like 1
  • Thanks 1
Link to comment
Share on other sites

13 hours ago, DLTcoins said:

Horn silver (AgCl) darkens with exposure to light. This is the principle on which black and white photography is based.

And hence why you can often use photographic fixer as a source of sodium thiosulfate. What I'm surprised about is just the extent of it, not that it happens. I've just not seen one of my own coins with horn silver darken like that. Then again, on second look, I think the significant differences in the photography between the first and second photo may having the most effect on the apparent darkening.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...