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 Replies: 8 / Views: 3,972 |
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Valued Member
United States
171 Posts |
I am new to the forum! I have a question that I have not been able to find an answer to anywhere. What effect does normal PVC off gassing have on coins? I have had the bulk of my collection in a vinyl binder with PVC-free archival-safe coin pocket pages and 2 by 2 cardboard Mylar windowed holders for nearly seven years. I have always known that PVC damages coins because of the oily plasticizers they put in the plastic. I keep my collection in a Sentry safe with lots of silica gel, and have never had problems with moisture or anything. The humidity in my house is usually in the 50's but can in certain times of the year get up into the 60's. My understanding from extensive research is that the PVC plasticizers are acidic when they leech out of the PVC and then react with the coin metal. Some say it's hydrochloric acid, but that makes no sense to me because neither silver nor copper react with HCL, and they're the type of coins most affected by PVC damage. I have recently removed all my pocket pages with the coins in them from the vinyl binder, and they have a faint shower curtain smell. I got paranoid, so I broke out one of the coins from its holder. The coin itself wasn't sticky or anything and smelled like coin metal. The outside of the holder had a faint PVC smell but the inside didn't. I assume the PVC smell will go away on its own eventually, but my concern is that my coins will develop PVC damage. None of them have as of yet, and they look the same as they did when I put them in there years ago. Am I correct in assuming that PVC green goo can only be caused by the plasticizer oil coming in direct physical contact with the coin?
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Pillar of the Community
Australia
2180 Posts |
I have heard that the gases can do damage (not just contact) but have no experience with it myself.
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CCF Advertiser
United States
1533 Posts |
PVC is plasticized with phthalates which deposit on the surfaces of the coin. They can make the green goo. PVC comes unplasticized as well. It is very stiff and brittle unplasticized, but it still has its uses. The PVC itself does decompose into vinyl chloride and HCL. I don't know where you heard HCl doesn't interact with silver, but that is not right. The acid can damage the coins, but its a slow process. By far the biggest danger is the phthalates which gives PVC flips that greasy feel. They are used at percent levels and leach out like nobody's business.
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Valued Member
 United States
171 Posts |
Scientists say HCL can't react with silver or copper or gold. Through my research, it's the plasticizers alone that are the culprits. HCL does react with bronze and steel though. Thank you for the information. I will be getting a new safe binder soon, but I still want to know if PVC green goo can only occur if the plastic is directly touching the coin. In other words, will my coins be ok now?
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Bedrock of the Community
United States
20753 Posts |
Quote:
Scientists say HCL can't react with silver or copper or gold. AgCl is actually one of the many standard forms of Silver found in nature. HCl is actually Hydrogen and Chlorine or Hydrogencloride. Chlorine can and actually does react with many metals. Gold is thought to be inert but it is not. It does react with Chlorine to form AuCl3. Gold also reacts with Florine, Cyanide and Mercury. Au2S is the dark discolorization on Gold. People with pools use a lot of Florine and as that gas evaporates, it can work it's way into a house where coins are and effect them. Metals are NOT inert. Some just react more slowly than others and with less and less other substances. |
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Pillar of the Community
 United States
7934 Posts |
The phthalates from PVC pages should not be able to get through the mylar windows in your 2 x 2. Mylar (biaxially oriented polyester) is very resistant to permeation by even small molecules like water vapor and oxygen. Large molecules like phthalates can't penetrate it to any significant extent.
I have coins in 2x2s that have sat in PVC pages for 45+ years. No problems. Although the pages are now falling apart.
As pointed out by @andrew, do not use PVC "flips" to store your coins.
Edited by tdziemia
10/25/2020 10:34 am
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Pillar of the Community
United States
7934 Posts |
Quote:
Scientists say HCL can't react with silver or copper or gold. That pertains to reaction with those pure metals. Coins are never pure metals, and acid CAN react with many elements like zinc, nickel, tin, lead which will be present in coins. Spots on the surface of modern gold coins have been linked to metallic impurities in the gold, or deposited on its surface, which then react with substances in the air. |
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Bedrock of the Community
United States
19935 Posts |
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Scientists say HCL can't react with silver or copper or gold. I'm a scientist and I can tell you with certainty that those metals all react with HCl with gold being the most resistant (requires special conditions). If what you said was true, we wouldn't have silver chloride, copper chloride and gold chloride. All three compounds exist without a shadow of doubt. Edited by BadThad
11/01/2020 11:37 am
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Pillar of the Community
United States
7934 Posts |
Those chlorides are normally formed by the reaction of the metal with elemental chlorine (Cl2), not hydrochloric acid.
Edited by tdziemia
11/01/2020 2:38 pm
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Replies: 8 / Views: 3,972 |
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Posted 10/24/2020 10:37 pm
