How can you tell the differenct between PVC damage and corrosion on copper coins, particulary large cents?
If it is PVC damage, do I use one product, such as acetone, and if it is corrosion, do I use another, such as Verdi-Care?
Corrosion typical makes a coin appear to have porosity, while PVC residue only affects a coin's surfaces. -Brian
PVC damage starts as a greasy sometimes shiny light green slime, sometimes a more thin almost layer like film, later it can bead up or come together in splotches, eventually turning a darker green and hardening. It will eat into the coin surface at this stage and become very difficult to impossible to remove as it reacts and bonds. Eventually it will become very dark green to or black and hard as the surface of the coin. At that point, it has eaten away at the surface and there will be pitting and corrosion under the PVC on the surface and into the coin. Catching it early is probably the only hope. Verdigris is natural oxidation on copper. Steel rusts, copper and brass oxidize in this green appearance. You can tell the difference easily with experience between PVC and verdigris. Verdigris will eventually get below the surface of the coin and pit the coin and corrode it since it is oxidation. It can be arrested and conserved but in both cases, the damage is done. PVC is far less desirable to find on your coins than verdigris. One is a natural occurrence, the other is a a result of improper storage in the wrong kind of plastic.
I have used both in that way, it does not always work, practice on common junk coins with these problems before trying to conserve your better coins with problems. Sometimes you eat the bear.... sometimes the bear eats you!
A coin dealer sold me flips with PVC a couple of years ago and I put all my miscellansous coins in them, not knowing there would be a problem. I've switched them into flips that don't have PVC. How much damage can occur in 2 years? (I can't tell by looking at them--there are more than 150--if there is damage or not. A lot of my large cents have green, but I think it's more likely it is from corrosion.)
It depends on the holders containing PVC and I would think age of the holders and storage factors would make a difference. I think, but I am not sure, that warmer storage would accelerate the breakdown of the chemicals in the "bad" plastic coin holder products. These type holders are sometimes described as smelling like a newly opened package of shower curtains. See if you can post some images of coins that concern you. People here may be able to say whether it looks like PVC or verdigris.
PVC contaimination leads to PVC damage which is corrosion. Once the metal is visibly corroded, it can't be reversed. Iyt may be disguised by toning, darkeners, or fillers, but it is still there. PVC contamination can be removed with acetone ( as per your other thread), PVC damage, if it is still microscopic level can be helped with the Verdi-Care type of products from BadThad ( I like his products, they do as he claims, but often people expect more ) pitting PVC corrosion is there for good. Acetrone will remove the PVC softener chemicals from the coin and halt the activity, although regular moisture can attack that area more vigorously than the patina on the coin that hasn't had PVC damage. Acetone won't dissolve metal, so it won't increase corrosion. Verdicare can help protect it, but the key is the owner protecting it from environmental damage. On the shower curtain smell, I use to say this all of the time, but now notice that Walmart ( local supplier of many things chinese ) have shower curtains from China that says "PVC Free" and do not smell like PVC Jim
Don't dispair, the 99 cent store still has the PVC shower curtains for those who want to have sniff reference. Train your dog to detect the smell, and bark 3 times when present
Acetone is a natural substance in our breath as it is a metabolic product from nutrient breakdown, especially if an excess of lipids are being broken down ( diabetics have higher conc. since they can't metabolism carbohydrates without sufficient insulin so are more dependent on lipids). The human breath of a normal human has about 100-150 ppm acetone, much more in untreated diabetes, or in starvation. Dogs have better smell, but the amount in the air wouldn't harm them. Plants and Animals have acetone in them also. So if your dog eats a lot of fats, smell their breath
