altyn Posted February 27, 2009 Report Share Posted February 27, 2009 I have noticed that many uncirculated silver coins, especially Maple Leaves, show white spots on the surface. Such spots can even be seen on coins still sealed in original plastic RCM holders. This is certainly not the same stuff as the normal dark tarnish (silver sulfide) that accumulates with time. Somewhere I read that this white stuff is silver chloride and there is no way to get rid of it. It also seems that the mint switched to packing coins in plastic rolls because of this problem. Does anybody know more about what this is and whether this white stuff can be removed? Link to comment Share on other sites More sharing options...
altyn Posted February 27, 2009 Author Report Share Posted February 27, 2009 Wikipedia says "Upon illumination or heating, silver chloride converts to silver (and chlorine), which is signalled by greyish or purplish coloration to some samples. Also when silver chloride is left in the sun it turns purple." So, if a coin with white spots is left alone by a window, the stuff might be gone (but something else might be acquired in its place). Anybody having experimented? Link to comment Share on other sites More sharing options...
just carl Posted February 27, 2009 Report Share Posted February 27, 2009 This is certainly not the same stuff as the normal dark tarnish (silver sulfide) that accumulates with time. Somewhere I read that this white stuff is silver chloride and there is no way to get rid of it. It also seems that the mint switched to packing coins in plastic rolls because of this problem. Does anybody know more about what this is and whether this white stuff can be removed? Exactly where does Silver Sulfide come from? Usually this is a by product of Hydrogen Sulfide or Sulfate. And that is only in the air where Sulfur is burned. Do you live in an area where sulfur is burned? Exactly how does this accumulate with time? All this is confusing since the burning of sulfur products is seldom done anymore anywhere. And Silver Chloride could be what you see but then too, just where is this coming from. Note that Silver Chloride would have to be formed by exposure to Chlorine in solution and with normally a Sodium type Chlorinated Salt. However, those white spots have been found more and more lately and many are saying they think it comes from the Chlorine that is used to make the plastic containers for the coins. Also, not possible. So the answer to your problem is if Acetone will not remove it, probably not much else will without leaving a mark. Link to comment Share on other sites More sharing options...
altyn Posted February 28, 2009 Author Report Share Posted February 28, 2009 Exactly where does Silver Sulfide come from? There are always minute amounts of sulfur compounds in the air, regardless of any industrial activity. This is how the normal patina is formed over the time. Actually that is not my question. But how can silver chloride be formed, unless the holder or the coin were contaminated with something at the mint, and is it really chloride, that's what I do not know. Acetone won't work if this is chloride. I guess people must have tried - this is the first thing that comes to mind. Link to comment Share on other sites More sharing options...
Mark Stilson Posted February 28, 2009 Report Share Posted February 28, 2009 I don't think anybody has found a way yet to remove them. PCGS was supposed to have a reward for anyone who could figure it out without harming the coin. Can't find an actual articlethough on PCGS just references on the board. Link to comment Share on other sites More sharing options...
thedeadpoint Posted March 1, 2009 Report Share Posted March 1, 2009 The PCGS X Prize! Link to comment Share on other sites More sharing options...
Mo! Posted March 1, 2009 Report Share Posted March 1, 2009 One of my mercury dimes has each detail as a black color. It actually looks really good. Link to comment Share on other sites More sharing options...
just carl Posted March 5, 2009 Report Share Posted March 5, 2009 There are always minute amounts of sulfur compounds in the air, regardless of any industrial activity. This is how the normal patina is formed over the time. Actually that is not my question. But how can silver chloride be formed, unless the holder or the coin were contaminated with something at the mint, and is it really chloride, that's what I do not know. Acetone won't work if this is chloride. I guess people must have tried - this is the first thing that comes to mind. Yes and no. The so called Patina formed is usually not from Sulfur although Sulfur gets blamed for this on all Copper products. Coins as an example. What you think is from sulfur is in reality the normal Cu combining with O to form CuO. This further combines with CO2 + H (OH) to form [CuCO3-Cu(OH)2], Copper Carbonate. THAT is the so called Patina formed over time. Back to the Silver problem. If it was blackesh then that would be easy since Silver combines so readily with Nitrates. But those Whitesh Milky spots on Silver is rather a mystery. They have been reported many times on coins from the Mint in so called sealed plastic containers. They also have appeared on coins in 2x2's, albums and even in plastic rolls. The problem is basically that Silver combines with so many substances, many are milky looking, that without a chemical analysis, they could be anything. On some people have reported they come right off in Acetone. Others say Acetone has no effect. This would obviously mean that either people are lying or the spots are different substances. The best thing is to try soaking in distilled water and/or Acetone. If these don't work, further attempts may make the coin look worse. IF, and that is a big IF, the coin is not really expensive and you want to experiment, A very brief dip in jewelry cleaner from Walmart might work. Some say Xylene also works better than Acetone. Again, if not an expensive coin and you find out something by such experiments, let us all know. Link to comment Share on other sites More sharing options...
altyn Posted March 6, 2009 Author Report Share Posted March 6, 2009 Thanks just carl, but sorry for some confusion that I might have caused by applying the word "patina" to silver. Tarnish or toning would have been better, while the term patina is usually applied to copper (as I know now). Anyway, the white stuff that I was talking about obviously is not patina, nor is it tarnish. My coin with white spots is not expensive - just a maple leaf and I got it close to the spot price. I will probably experiment. But if PCSG does give a lot of bucks for finding a solution to this problem, then I will keep it secret when (or if) I find it (a big IF). Cheers. Link to comment Share on other sites More sharing options...
just carl Posted March 8, 2009 Report Share Posted March 8, 2009 My coin with white spots is not expensive - just a maple leaf and I got it close to the spot price. I will probably experiment. But if PCSG does give a lot of bucks for finding a solution to this problem, then I will keep it secret when (or if) I find it (a big IF). Now that is not nice. We all want to know. Remember one thing. Such experimenting may be fun and the results many come in handy for more valuable coins. HOWEVER, the utilization of chemicals to do such experiments may be more expensive and usually dangerous than the end product is worth. I say this due to in the past I've attempted to remove spots, toning, tarnishing, etc and sat down and figured out that such experiments create a coin worth a lot of money in substances used and seldom any good results. Then such coins are dumped back into circulation and found by someone and we then end up with another post asking WHAT HAPPENED TO THIS COIN. Link to comment Share on other sites More sharing options...
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