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<p>[QUOTE=&quot;SilverWilliesCoinsdotcom, post: 2933371, member: 86795&quot;]from <a href="https://www.ist.fraunhofer.de/content/dam/ist/en/documents/thomic_silberreinigung_en.pdf" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://www.ist.fraunhofer.de/content/dam/ist/en/documents/thomic_silberreinigung_en.pdf" rel="nofollow">https://www.ist.fraunhofer.de/content/dam/ist/en/documents/thomic_silberreinigung_en.pdf</a></p><p><br /></p><p>Anyone have any experience with this technique?</p><p><br /></p><p>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&nbsp; &nbsp; <span style="color: #ff4d4d">edited</span>[/QUOTE]</p><p><br /></p>

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