Question about chemical reaction with sealed mint silver bar
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I know this isn't a coin, however i am hoping an expert could explain the chemical reaction that has happened. The silver bar was orange/red colored on a reeded  edge. It was sealed by the  mint. As it didn't appear to be normal tarnishing I broke the seal and washed it  in distilled water with a spritz of dawn detergent. Immediately the spritz foam turned orange/red. Upon rinsing the discoloration had completely disappeared and the bar looks like new. 
 

I am aware of green slim caused by PVC as i have a couple of Lexington commemoratives that had the slime problem.  Is the problem on the bar similar to the reaction with pvc, sulfer maybe? Would appreciate any thoughts on this.  

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The detergent reaction suggests organic contamination -- but in a U.S. Mint-sealed container? Are the containers actually air tight?

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On 5/31/2022 at 8:07 PM, RWB said:

The detergent reaction suggests organic contamination -- but in a U.S. Mint-sealed container? Are the containers actually air tight?

Sorry i should have been more specific. The silver bar was produced by the Republic Metals Corporation which filed for bankruptcy and their assets were  acquired by ASAHI Holdings in 2019. The bar was sealed by RMC. There were no apparent leaks, but apparently it was not air tight. Ive never seen organic contamination this color. Thank you for suggesting that. 

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If Dawn dispersed it, then it wasn’t sulfur, which bonds incredibly tightly to silver, so much so that it requires some pretty fancy chemistry to remove it. Perhaps some sort of surface preservative or even a lubricant at work there. 

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Might have occurred before the bars were packaged....? Since the containers were not air tight, lots of things could have happened, You might try storing them as-in in a tightly sealed box with several packets of silica gel and sulfur absorbent archival sheets. This can sometimes lessen the appearance and damage....if there is any.

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