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Correct way to make 5% solution of sodium sesquicarbonate for Bronze Disease treatment.
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<p>[QUOTE="Theodosius, post: 3622626, member: 77077"]So now for some results of the treatment I performed. I got a group of nice Greek bronzes as part of a lot. Several of these broke out in BD shortly after I received them. They all exhibited light green, fluffy patches to an alarming degree. I soaked them in individual covered cups (soy sauce to go cups) in the solution for around four months, removing the BD with bamboo skewers, nylon brushes, and sometime used dental picks for stubborn deposits. I changed the water daily at first, then weekly. The water would turn blue and bluish deposits appeared at the bottom of the cups.</p><p><br /></p><p>I noticed a few different effects. Some of the coins had BD under their patinas; these patinas flaked off and were lost. Some had areas where the patinas dissolved, while in other areas the patinas remained hard and intact. The fluffy green deposits sometimes turned into darker, hard, stable green deposits. Under the fluffy deposits were soft reddish areas that appeared to be bronze that was partly converted into some salt or oxide, these areas were pretty much lost as well over the treatment. It was necessary to remove any fluffy green stuff to expose the additional BD underneath or a crust would form encapsulating the BD and preventing it from being treated.</p><p><br /></p><p>Finally, and most surprisingly to me, all the coins developed a distinctive blue coating, that I have seen before on other bronzes, and I suspect is the result of this treatment. It is not unattractive, and I suppose it could form naturally on bronze coins exposed to sodium compounds, but I can't help but feel these are BD coins in remission or recovery. I am not sure if there is a way to avoid this blue coating developing. It seems to be thicker on the downward side of the coin. I would alternate orientations each week to expose the two sides evenly to the solution which may have caused the blue coating to be more even between the sides. I am guessing some compound was forming in the solution through the action of the sodium compounds and it was floating around and reacting with the bronze surface of the coin.</p><p><br /></p><p>After the extended soaking, I rinsed the coins repeatedly in distilled water and left them out on my desk for 3 months. I wanted to see if the BD returned and if any further changes occurred. So far, they all look to be stable. I think that multiple months were required for the treatment to be effective. After one month I was starting to think it would not work, but other coins came and took up my attention so it was easy to just keep treating them to see what would happen.</p><p><br /></p><p>Here are three of the patients. I should have taken before and during pictures, but l did not realize starting out that this would turn into a case study. <img src="styles/default/xenforo/clear.png" class="mceSmilieSprite mceSmilie10" alt=":oops:" unselectable="on" unselectable="on" /></p><p><br /></p><p>[ATTACH=full]971299[/ATTACH] Zeugitana, Carthage. 300-264 BC.</p><p>Æ 19mm 5.47gms. Sardinian mint.</p><p>Obverse: Wreathed head of Tanit left.</p><p>Reverse: Horse's head right; globe to right.</p><p>References: SNG Copenhagen 164.</p><p><br /></p><p>A nice coin in hand, the blue coating it very obvious.</p><p><br /></p><p>[ATTACH=full]971300[/ATTACH]</p><p>SICILY, Syracuse. Hieron II. 275-215 BC.</p><p>Æ27, 27mm, 16.66 gms. Struck circa 230-218/5 BC.</p><p>Obverse: Diademed head left.</p><p>Reverse: Horseman riding right, holding couched spear in right arm; IEPΩNOΣ in exergue.</p><p><br /></p><p>Another case of the blues. This coin lost areas of patina around the edges and ended up with rougher surfaces.</p><p><br /></p><p>[ATTACH=full]971301[/ATTACH] SICILY, Syracuse. Timoleon and the Third Democracy. 344-317 BC.</p><p style="text-align: left"><span style="font-size: 16px"><font face="Verdana"><span style="color: rgb(20, 20, 20)">Æ Hemidrachm, 24mm, 16.08 gms.</span></font></span></p> <p style="text-align: left"><span style="font-size: 16px"><font face="Verdana"><span style="color: rgb(20, 20, 20)">Timoleontic Symmachy coinage. 1st series, circa 344-339/8 BC.</span></font></span></p> <p style="text-align: left"><span style="font-size: 16px"><font face="Verdana"><span style="color: rgb(20, 20, 20)">Obverse: Laureate head of Zeus Eleutherios right.</span></font></span></p> <p style="text-align: left"><span style="font-size: 16px"><font face="Verdana"><span style="color: rgb(20, 20, 20)">Reverse: Upright thunderbolt; to right, eagle standing right.</span></font></span></p><p><br /></p><p>This coin's entire patina was lost. The BD could be seen poking through small holes in the original patina. Over time the (very thin) patina flaked off. The bronze underneath is fairly smooth and the coin is still nice in hand. I believe this coin and the previous were on the way to complete destruction. I had two more small bronze coins where the BD was coming up from inside the coins. The BD was eventually stopped on them, but so much of the surface was lost that they were basically ruined as coins:</p><p><br /></p><p>[ATTACH=full]971307[/ATTACH]</p><p><br /></p><p>I did not even try to attribute these guys. The green looks light like BD, but it is hard and stable.</p><p><br /></p><p>Could the blue coating on these coins be removed using some other chemical treatment? Maybe, but what other affects will that have on the bronze? It certainly does not come off from brushing with nylon or soaking in distilled water. I prefer to leave these alone for now. I think I have saved them, and that is good enough.</p><p><br /></p><p>I think the lesson I learned is that BD can be stopped using this treatment but it takes time. The patina may or may not be affected, but you won't end up with a shiny copper coin when you are done at any rate.</p><p><br /></p><p>John[/QUOTE]</p><p><br /></p>
[QUOTE="Theodosius, post: 3622626, member: 77077"]So now for some results of the treatment I performed. I got a group of nice Greek bronzes as part of a lot. Several of these broke out in BD shortly after I received them. They all exhibited light green, fluffy patches to an alarming degree. I soaked them in individual covered cups (soy sauce to go cups) in the solution for around four months, removing the BD with bamboo skewers, nylon brushes, and sometime used dental picks for stubborn deposits. I changed the water daily at first, then weekly. The water would turn blue and bluish deposits appeared at the bottom of the cups. I noticed a few different effects. Some of the coins had BD under their patinas; these patinas flaked off and were lost. Some had areas where the patinas dissolved, while in other areas the patinas remained hard and intact. The fluffy green deposits sometimes turned into darker, hard, stable green deposits. Under the fluffy deposits were soft reddish areas that appeared to be bronze that was partly converted into some salt or oxide, these areas were pretty much lost as well over the treatment. It was necessary to remove any fluffy green stuff to expose the additional BD underneath or a crust would form encapsulating the BD and preventing it from being treated. Finally, and most surprisingly to me, all the coins developed a distinctive blue coating, that I have seen before on other bronzes, and I suspect is the result of this treatment. It is not unattractive, and I suppose it could form naturally on bronze coins exposed to sodium compounds, but I can't help but feel these are BD coins in remission or recovery. I am not sure if there is a way to avoid this blue coating developing. It seems to be thicker on the downward side of the coin. I would alternate orientations each week to expose the two sides evenly to the solution which may have caused the blue coating to be more even between the sides. I am guessing some compound was forming in the solution through the action of the sodium compounds and it was floating around and reacting with the bronze surface of the coin. After the extended soaking, I rinsed the coins repeatedly in distilled water and left them out on my desk for 3 months. I wanted to see if the BD returned and if any further changes occurred. So far, they all look to be stable. I think that multiple months were required for the treatment to be effective. After one month I was starting to think it would not work, but other coins came and took up my attention so it was easy to just keep treating them to see what would happen. Here are three of the patients. I should have taken before and during pictures, but l did not realize starting out that this would turn into a case study. :oops: [ATTACH=full]971299[/ATTACH] Zeugitana, Carthage. 300-264 BC. Æ 19mm 5.47gms. Sardinian mint. Obverse: Wreathed head of Tanit left. Reverse: Horse's head right; globe to right. References: SNG Copenhagen 164. A nice coin in hand, the blue coating it very obvious. [ATTACH=full]971300[/ATTACH] SICILY, Syracuse. Hieron II. 275-215 BC. Æ27, 27mm, 16.66 gms. Struck circa 230-218/5 BC. Obverse: Diademed head left. Reverse: Horseman riding right, holding couched spear in right arm; IEPΩNOΣ in exergue. Another case of the blues. This coin lost areas of patina around the edges and ended up with rougher surfaces. [ATTACH=full]971301[/ATTACH] SICILY, Syracuse. Timoleon and the Third Democracy. 344-317 BC. [LEFT][SIZE=16px][FONT=Verdana][COLOR=rgb(20, 20, 20)]Æ Hemidrachm, 24mm, 16.08 gms. Timoleontic Symmachy coinage. 1st series, circa 344-339/8 BC. Obverse: Laureate head of Zeus Eleutherios right. Reverse: Upright thunderbolt; to right, eagle standing right.[/COLOR][/FONT][/SIZE][/LEFT] This coin's entire patina was lost. The BD could be seen poking through small holes in the original patina. Over time the (very thin) patina flaked off. The bronze underneath is fairly smooth and the coin is still nice in hand. I believe this coin and the previous were on the way to complete destruction. I had two more small bronze coins where the BD was coming up from inside the coins. The BD was eventually stopped on them, but so much of the surface was lost that they were basically ruined as coins: [ATTACH=full]971307[/ATTACH] I did not even try to attribute these guys. The green looks light like BD, but it is hard and stable. Could the blue coating on these coins be removed using some other chemical treatment? Maybe, but what other affects will that have on the bronze? It certainly does not come off from brushing with nylon or soaking in distilled water. I prefer to leave these alone for now. I think I have saved them, and that is good enough. I think the lesson I learned is that BD can be stopped using this treatment but it takes time. The patina may or may not be affected, but you won't end up with a shiny copper coin when you are done at any rate. John[/QUOTE]
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Correct way to make 5% solution of sodium sesquicarbonate for Bronze Disease treatment.
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