Cleaning Silver - Plasma Cleaning legit?

from https://www.ist.fraunhofer.de/content/dam/ist/en/documents/thomic_silberreinigung_en.pdf

Anyone have any experience with this technique?

Cleaning silver with atmosphericpressure plasma Silver or silver alloy surfaces discolor over time in air: they become tarnished. The reason why tarnishing occurs is to be found in the sensitivity of the silver surface to sulfurous gases, such as are present in small quantities in the ambient air. Even at room temperature hydrogen sulfide reacts with silver to form silver sulfide, with brownish-black discolorations appearing on the surface of the silver. silver-plated objects and also for items which do not have a smooth and even surface. Every time the item is polished, some of its original substance is lost and thereby a part of the cultural heritage. Silver reduction in atmospheric-pressure plasma A discharge is ignited in a plasma nozzle working at atmospheric pressure, carried outwards by the gas flow of a nitrogen-hydrogen mixture and brought into contact with the tarnished material. Due to the action of the reductive gas mixture the tarnished surface deoxidizes and the black discoloration disappears. The major advantages of plasma treatment: „ No loss of material „ Cleaning of highly sensitive exhibits possible „ Targeted local treatment „ Simple to use: the plasma nozzle is guided over the item like a pen „ Easy to monitor – unlike low-pressure processes Preservation of cultural heritage Works of art and other cultural objects are valuable witnesses in providing information about cultural movements, past customs, materials and technologies. Frequently, however, these objects are put at risk due to weathering, environmental influences, corrosion or microbial attack. In conjunction with five other Fraunhofer institutes the Fraunhofer IST, within the Cultural Heritage Research Alliance, is developing ways of using plasma technologies for preserving our cultural heritage and thus expanding the range of restoration methods. Scientists at the Fraunhofer IST have been researching for some time into the careful cleaning of silver by means of atmospheric-pressure plasma. Problems in conventional silver polishing The silver sulfide must be removed from time to time for the silver surfaces to gleam as they should. Conventionally, restorers work with an abrasive mixture of calcium carbonate and water, known as whiting. This method does, however, present problems, particularly for thin-walled, delicate and 1 2 Application examples This method is of interest for historical textiles in which textile and metal are present in a fixed, inseparable association – such as, for example, tapestries of silk and silver. Conventional cleaning methods not only result in loss of substance in the case of the silver but also have a damaging effect on the silk proteins. Plasma treatment can be a protective alternative here. Another area of application is very fragile objects which deform plastically under mechanical polishing. Since the atmospheric-pressure plasma process is a contactless method, silver sulfide can be removed without deforming the object. Outlook To what extent other compounds occurring on silver objects, such as, for example, silver chlorides and sulfates, and even copper compounds, can also be reduced in the plasma is currently still under investigation. 1-2 Silver-plated tea pot before and after a reductive treatment with atmosphericpressure plasma. 3 Stereomicrograph in 6.5x magnification of a textile with integrated silver threads. Contact edited

 

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I can't comment on the process or how it would work on coins, but the Fraunhofer Institute is a top notch research facility in Germany, so their claims should be legit.

 

Dangit, someone beat me to it! I've been wanting to try hydrogen plasma on silver (and even copper) for years. That instinct for self-preservation is hard to overcome, though.

I do wonder how it would work for coin restoration -- sure, it might take away the sulfur without carrying off the silver, but that leftover silver isn't going to fit into the metal's structure the same way it did before the sulfur came along. I'd love to see some before-and-after microscopy (and better yet, electron microscopy)...

 

Can't wait to see it used on on badly tarnished coins.

 

Don't bet money on that.

 

Why? Do you think the sulfur atom is small enough to fit into the FCC structure without distortion, or do you think the toning is monoclinic Ag2S and the lattice structure can easily rearrange back into FCC once the S atoms are removed?

As @-jeffB said, an SEM pic of the microstructure would be very helpful.

 

Since a TPG grader only uses a 5X magnifier , as heard on CT, I wonder how small someone could engrave their name with a micro discharge and not have it visible enough to be noticed ?

 

IBM was moving atoms over 25 years ago.

I wonder if they can do @GDJMSP on a Morgan dollar

 

Interesting. Since they say the plasma can be used on cloth, it can't be too hot. The only plasmas I know anything about are HOT. A lead storage battery works by lead going to lead sulfate on the discharge and by the lead sulfate going back to lead on the recharge. No loss of material, except that the regenerated lead is not as "intact" as the original lead and eventually sloughs away and the battery shorts out. I just wonder if the regenerated silver would be as structurally sound as the original silver.

 

Interesting....

https://en.wikipedia.org/wiki/Nonthermal_plasma

For the nerds:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4016545/

 

The second law of thermodynamics, which states that the entropy (randomness) of a closed system always increases, dictates that the structure of the silver is altered by the oxidation and this alteration can not be reversed.

 

The more I read about this technology, the less confidence I have in BRILLO.

 

The question is not whether it goes all the way back. Clearly it can't for all the reasons stated. The question is scale. Can it be detected at the scale at which coins are graded? I'll tell you this, NO TPGS has been able to detect any "dip" of my formula yet - not on a business strike, not on a brilliant proof. I'm still batting 1.000. And that includes a coin (just one) that was in the dip for AN HOUR! The working difference between a dip using citric acid vs. sulfuric acid is both REAL and IMPORTANT!

 

EXACTLY!!!

 

Find a highly tarnished 21 Morgan - put it through the process - if it looks good - send it to a TPG and get grade results.

 

But this isn't a closed system at all. They're pumping plenty of energy through it. (Heck, think about turning silver-bearing rock into a lump of .999, then turning that into a PR70 coin, then "toning" the coin into a pile of silver sulfide, then refining that back into silver, then striking it...)

What they aren't doing, I assume, is any kind of fine-grained process that would actually put the silver back into the right place on the coin being treated.

IBM's push-atoms-around scanning-tunneling equipment can put individual atoms into individual spots, but you'd spend millennia restoring a single coin that way. Molecular-beam epitaxy is very old technology, and can lay down single-atom-thick layers across something much larger than a coin, but it's overkill, too -- I'm guessing that you could lay down a layer with convincing luster, but even a restored 1794 dollar wouldn't pay back your expenses, I think.

Is this plasma process better than current dipping processes? Could be. I'm watching with interest. (But only watching; still not bold/foolish enough to set up a tank of hydrogen indoors and start running it through RF discharges...)

 

Perhaps I didn't read closely enough, but how does one acquire (or borrow) this technology?

 

No it doesn't because this is not a closed system.