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<p>[QUOTE=&quot;Roerbakmix, post: 8416936, member: 100731&quot;]I&#039;ll repeat here what I&#039;ve answered in a private message of [USER=119259]@ArtDeco[/USER]. This is a coin that would not improve with sodium thiosulphate, in my opinion. </p><p><br /></p><p>----</p><p><br /></p><p>&nbsp;I&#039;ve actually posted a more detailed walktrough, which can be downloaded at my researchgate profile: <a href="https://www.researchgate.net/project/Ancient-coin-restoration" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://www.researchgate.net/project/Ancient-coin-restoration" rel="nofollow">https://www.researchgate.net/project/Ancient-coin-restoration</a></p><p><br /></p><p>While most coin restorers don&#039;t share their methods, I decided to share some of my techniques to save coins from unexperienced collectors.</p><p><br /></p><p>Regarding the denarius of Hadrian which you posted: it really is fine as it is. The patina, even though it may be darker in real life, is the process of the coin being deposited in the ground over the last c. 1800 years. There are no horn silver deposits, though there are some earth deposits on the obverse.</p><p><br /></p><p>If you really insist on brightening the coin, there are a few options:</p><p>1) thouroughly rinse the coin under flowing tapwater, by rubbing the coin between your thumb and finger. This will probably remove the (darker) earthen deposits on the obverse, and the (mild abrasive) rubbing will slightly lighten the patina</p><p><br /></p><p>if unsatisfactory:</p><p>2) apply a very minute amount of baking soda (NaHCO3) and repeat (1).</p><p><br /></p><p>if unsatisfactory:</p><p>3) repeat 2, but now rub a small piece of aluminium foil. This will cause a redox-reaction with the NaHCO3, which will remove the silver sulphide (= the black patina).</p><p><br /></p><p>Note that baking soda is abbrasive and will, if rubbed for too long, polish the coin.</p><p><br /></p><p>Having said this all, remember that there are many cleaned coins on the market, and only a small hand full have the desired black patina your coin has - many ancient coin collectors will pay a premium for the patina your coin has.[/QUOTE]</p><p><br /></p>

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