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<p>[QUOTE=&quot;Roerbakmix, post: 7939787, member: 100731&quot;][USER=89970]@Fugio1[/USER], this is a difficult coin to clean. Not because of the encrustation, which will dissolve easily in sodium thiosulphate, but because of the lustrous yellow patina. </p><p><br /></p><p>Immersing the coin in sodium thiosulphate would definitely affect the toning: the coin will turn dark grey to black. See: <a href="https://www.cointalk.com/threads/hieronymus-of-syracuse-restoration-of-a-valuable-coin.365640/" class="internalLink ProxyLink" data-proxy-href="https://www.cointalk.com/threads/hieronymus-of-syracuse-restoration-of-a-valuable-coin.365640/">https://www.cointalk.com/threads/hieronymus-of-syracuse-restoration-of-a-valuable-coin.365640/</a> </p><p>In this thread, I restore a 10 Litra piece of Hieron (which sold for $1100 at CNG, if I remember correctly). The effect on that coin was dramatic (but expected): it turned black entirely. As I&#039;ve explained in other posts, this black deposition can be removed easily, but the overall aspect of the coin will be different. </p><p><br /></p><p>Note that this deposition will easily dissolve, as mentioned. I classify this as &#039;granular with sharp borders&#039;:</p><p>[ATTACH=full]1374010[/ATTACH] </p><p>which is the same deposit as on the coin of Hieron in the beforementioned thread, and also the same as in this thread: <a href="https://www.cointalk.com/threads/cleaning-a-sceatta.370033/" class="internalLink ProxyLink" data-proxy-href="https://www.cointalk.com/threads/cleaning-a-sceatta.370033/">https://www.cointalk.com/threads/cleaning-a-sceatta.370033/</a> (second post):</p><p><img src="https://www.cointalk.com/attachments/upload_2020-11-20_9-55-16-png.1205787/" class="bbCodeImage wysiwygImage" alt="" unselectable="on" /></p><p>after:</p><p><img src="https://www.cointalk.com/attachments/upload_2020-11-20_9-55-33-png.1205788/" class="bbCodeImage wysiwygImage" alt="" unselectable="on" /></p><p><br /></p><p>Back to your coin: how to proceed? </p><p><br /></p><p>First, if you&#039;re totally unexperienced, I would recommend against restoration. Otherwise, I would advice the following steps:</p><p>1) prepare a solution of sodium thiosulphate in distilled H2O. Use a strong solution, e.g. 10g in 20 ml of H2O. </p><p>2) with a pipette: remove about 5 ml from the solution, and add to 5 ml of glycerol (also known as glycerine). This will increase the surface tension: Without the glycerine, the surface tension will be too low, and the droplet will spread out to on the surface of the coin (see here: <a href="https://www.cointalk.com/threads/playing-around-with-hydrochloric-acid-cleaning-my-avatar-coin.383989/" class="internalLink ProxyLink" data-proxy-href="https://www.cointalk.com/threads/playing-around-with-hydrochloric-acid-cleaning-my-avatar-coin.383989/">https://www.cointalk.com/threads/playing-around-with-hydrochloric-acid-cleaning-my-avatar-coin.383989/</a> where I encountered a similar problem, but then with 30% HCl)</p><p>3) use a mechanical pipette, and place a small droplet of ~500 uL (0.5 ml) on another (silver) coin to test the surface tension. Preferably, you want to create a droplet which will not spread out on the surface of the coin, but that can be &#039;guided&#039; to stay on top of the deposit. Add more glycerine if needed. </p><p>4) if the solution is less than &lt;15 minutes old (sodium thiosulphate will degrade to elemental sulphur, amongst others, causing depositions of sulphur on your coin that are nearly impossible to remove): place the droplet on the deposit of your coin. </p><p>5) you will see that the deposit will dissolve easily. If not, use a droplet of acetone to remove any fatty layers that protect the AgCl from the sodium thiosulphate. </p><p>6) rinse the coin with water and gently scrub the (now weakened) deposit with your thumb. </p><p>7) repeat until finished (remember step 4 though!)</p><p><br /></p><p>I would advice against mechanical cleaning unless you really know what you&#039;re doing.[/QUOTE]</p><p><br /></p>

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