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<p>[QUOTE=&quot;altaycoins, post: 3110114, member: 16466&quot;]Let&#039;s clarify few things:</p><p>1) If it is verdigris, you don&#039;t need help. Verdigris is not harmful but a protective patina. If it was harmful, you wouldn&#039;t have the statue of liberty still erected. </p><p><br /></p><p>2) If it is bronze disease, first mechanically get rid of the green powder (copper chloride) as much as you can. Then, you can treat it with a 20% sodium sesquicarbonate solution. You need to change the solution every week, before dipping in fresh solution you can brush it gently with a soft brush. When it is done, you can bake it for a few hours at 200 degrees celcius. And try to keep it in a dry environment. </p><p><br /></p><p>3) Do not use harsh chemicals like ammonia, sodium hydroxide etc. Bronze disease is an autocatalytic reaction between copper and the chlorides. When there is humidity involved chlorides form hydrochloric acid which further reacts with the copper and forms copper chloride (CuCl2) which is powdery. As long as there is water (humidity) and the chlorides, it will continue to &quot;eat&quot; the copper. Strong chemicals destroys the patina but sodium sesquicarbonate treatment (also there is a benzotriazole treatment but the SSC is better) works best.</p><p><br /></p><p><br /></p><p>4) I am a total noob on Roman coins. What is the silver content in Roman coinage? The picture you posted doesn&#039;t look like it is bronze disease but a copper deposit. I have such silver coins and they are totaly OK. See below. Are you sure that they were not there but grew over time?</p><p><img src="http://altaycoins.com/sikke_paralari/65_2_63564_.jpg" class="bbCodeImage wysiwygImage" alt="" unselectable="on" />[/QUOTE]</p><p><br /></p>

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