Artificial toning - no eggs needed

[daverino]

I have been working with photo fixer solution to clean silver coins from horn silver and other encrustations. It also can create some beautiful artificial tones on modern silver coins. The solution is daubed on the coin and allowed to sit (5-12 hrs) and some marvelous colors develop. I tried it with some silver half-dollars in good condition but still "junk" silver. If the surface is still clean and bright it works very well. If not it creates a dull yellow tone on the coin as you see on one example

I decided to see how it fares with ancient silver so I pulled out my demetrius II T'drachm that could use some improved eye-appeal. I allowed the photo fix solution to dry to a crust on the coin and sit for a day. Results were minimal so I cleaned the surface with alcohol and tried again. The results were not too great but the coin is somewhat darkened and some yellow-gold tones appear on the coin in places.

Importantly, the "finish" on the coin is not affected. The coin is darker but the gloss remains. In hand, the area around the nose that was damaged by horn silver deposits stands out less than it did before so I think it is an improvement.  The 'original condition' photo is shown at bottom.

Dave

PS. I tried toning with a rotten egg - Forget it!!

[daverino]

Just as an addendum for all you chemistry buffs -you know who you are! - this is what I think happens. The ammonium thiosulfate (NH₄)₂ (S₂O₃ )in the fixer solution reacts directly with silver (Ag) on the surface of the coin to produce silver sulfide.

2 Ag + (NH₄)₂ (S₂O₃)  --> Ag₂S (patina) + SO₂ ( sulfur dioxide)+ 2NH₃ (ammonia)+ H₂O (water)

The bright colors are due to thin film effects - layers of patina which are on the order of the wavelengths of light so they will only show up as colors on smooth surfaces.

[Joe Sermarini]

Using a liquid to create toning does not replicate the natural processes.  It looks artificial.  US coin collectors don't want coins that have been cleaned at all.  They will know the difference and reject the liquid toned coins.  Harlan Berk has a DVD presentation on how to detect artificial toning and your examples don't pass.  Ancient coin collectors are a bit less picky about these things because ancient coins have usually been cleaned.  If it looks fake (and it does), ancient coin collectors won't like it either. 

[daverino]

Joe

    I am aware that you can't increase the value of US coins by artificial toning. The grading services don't allow it.  It only depends on whether you like your coins colorful or not. As for its effect on ancients, at least for the one coin on which I have tried it, I can't tell the difference between natural and artificial toning if in fact there is one. It is simply a modest overall darkening effect.

What I did not like about the original coin was its bright silver look that seemed very artificial to me

Regards, Dave