12s Lincoln Reveals Unpleasant Surprise; Your Thoughts?

I like to use a copper cent very harshly cleaned to bright copper with an SOS pad (or steel wool).

Not all that is green is verdigris.

Thanks again to everybody for even more great information. While everyone is being so helpful, how about we just do a complete primer on how to bag up your copper coins that are in holders? GSDykes suggest Hefty bags, which I assume means they are free of PVC and other toxins. BadThad adds to use a scrubbed copper for the sacrificial cent. (I'm digging through a bucket for pre-83's.) That leaves only the desiccant (which I just realized I have been spelling wrong). As with everything else numismatic, the obvious question: are some more appropriate than others in terms of purity? Finally, if I want to do one bag per slab, I assume someone makes such a thing without impurities? Thanks again for the warm welcome and good ideas. There's so much to learn.

Use pure silica gel beads in a Tyvek pack. Do not use moisture color-changing silica desiccants, as the gases they emit can be harmful. (i.e. no blue silica). I use 56 gram packs for a 2 1/2 gallon Hefty bag. [a bit over-kill, but thats the way I am]. Hefty bags are made of polyethylene, which is perfect for coins--I checked with the manufacturer. With Tyvek as the packaging, you can oven-dry the packs for re-use!! Which saves money. Tyvek melts at 200 degrees [F.] (actually about 230 degrees) so keep the oven set at no more than 200 degrees, and dry for several hours. Weigh the packs before drying, and compare after drying. I dry the packs about once per year. Tyvek packs of silica gel beads are tough, they can handle some wear and tear. If you have special coins (such as tin) do not allow to freeze, keep at room temperatures. Keep sulphides, salts, chlorides and certain oxides away from the coin environments. Also, most Coin supply stores supply small plastic "safe" baggies for slabs et al. [of course no PVC or bad stuff!].

All of this is cheap and easy to do, really. I buy the Tyvek packs in bulk (each packet weighs 56 gram packs, 20 packets at a time) off ebay. Hope this helps. There are also other gas absorbing items other than the sacrificial cent, but they cost a lot more! (i.e. "Corrosion Protection Kits", available from most larger coin dealers/shops).

Oh, by the way, you used the phrase "old copper," upthread, which I like. Just for fun, here's a photo of my latest arrival, combining the topics of old copper, keeping spots from growing, and unfortunately scratched holders, with a bit of wood thrown in for a bonus. I paid too much for this but I couldn't resist the stripes.

Beautiful 11D!

Where's the reverse pic?

Nice

That 11D rocks!