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Color change of PVC.
keets
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Can anyone speculate as to how long it takes PVC to become green and visible on coins?? I ask because it isn't green when it's in the flips or other plastic products, so the change must occur once it leaches from the plastic onto the coin.
Al H.
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I think pvc off gasses very slowly and is helped by warmth and moisture. Months and longer IMO. Peace Roy
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I think the environment would play a big part of your question.
I agree with the above...It takes quite a while and the environment will have a direct effect on the process... so a specific time period will vary....I do believe that no matter what the environment, continued exposure will result in contamination. The process is taking place, even when not visible, and can manifest visibly long after removal from the container. That is why PVC has been observed on some slabbed coins. Cheers, RickO
The process is taking place, even when not visible, and can manifest visibly long after removal from the container. That is why PVC has been observed on some slabbed coins.
this is really what my question is directed at. it doesn't seem as though PVC leaches from plastic onto a coin surface as a green substance, most likely it is either clear or milky white.
That is my observations Al....the initial deposition is invisible to the eye (may show up under UV, still trying to confirm that), then, as the chemical reaction with the metal progresses, it becomes milky, the progresses to the green, visible state. Cheers, RickO
Correct. There is no green component in the products of the thermal decomposition of PVC. The green that eventually appears, after PVC components deposit onto the surface of a coin, is mostly a hydrated copper (II) chloride. This is the product of a reaction between hydrochloric acid (one of the decomposition products) and the copper in the coin, and why removal of a heavy green blob can reveal a pitted surface underneath.
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I don’t know how long it takes, but I speculate that it can be a long time in some circumstances.
Before it turns green, you can often feel the PVC residue. It feels like a thin layer of ointment on the surface. It is a very noticeable difference from what a normal coin feels like. If you can feel it on the rim, it is also likely on both faces.
yeah, there have been a lot of times in the past when I was breaking apart collections and in looking at the coins I could feel the "slime" on the edge. it might be a good idea to assume PVC is on coins and to rinse in acetone to avoid later evidence. lately, I've been looking at a lot of coins which arouse my suspicion and cause a "pass" because of suspected PVC showing a light green or an off-grey color. not large areas, mainly spots.