Iridescent Green Toning On Copper

If you are referring to the 1-cent coins, they are all proof strikes and seem natural to me. You can get some pretty vivid colours on proof strike cents....

sel_69l - how do they need to be stored? I have several toned coins in slabs and working on an entire Indian cent toned proof collection.

Slabs are not air tight and should be stored with the same care as raw coins. The final storage step for any coin you're not handling on a daily basis should be an airtight container of some sort - I'm a big fan of food-grade Ziplock bags with the air pushed out - so humidity, atmospheric chemicals and above all oxygen cannot reach the surface of the coin.

thanks guys. I've been working on a vacuum chamber. it's been done, but there's a real slow leak. I could also use it to pump out the air in the slabs and back fill argon gas into the chamber and ultimately the slabs. i'll show the construction soon... so are there any folks in the community that I can call and ask other questions about toning? mainly copper toning. maybe someone on other forums? nobody at the local coins shows know anything...

maybe not airtight, but the diffusion of oxygen or moisture coming into the slab might be slowed... and maybe it won't help due to cycling low and high pressure weather systems throughout the years.

You can stop that diffusion completely by putting the slab into a ziplock bag. Why go to the effort?

just carl - soldering the edges and dunking in water is a very interesting idea! I was thinking of a test today and thought about drilling a hole and sealing in an oxygen sensor in the slab after sucking out the air and back filling with nitrogen and monitor the oxygen levels over the weeks/years.

superdave - also thought about a sealed bag, but I'm not sure how I'd like looking at the coin through yet another barrier. it probably wouldn't be much of an iddue though. I've made my vacuum chamber large enough to fit an entire dansco album laying flat. (will show in the future)

badthad - after drawing out the air in the slab, you could back fill the chamber (and slab) with an inert gas like nitrogen or argon. maybe leave the slab in the nitrogen filled chamber over time to allow the pressure acclimation. I've get several Lincoln proof coins in slabs with amazing orange/purple toning graded as Red that only could have toned in the slab.

If you're planning to permanently maintain an inert gas storage container for the slab for as long as you own the coin, that would be fine. If not, no matter what you do, the gas will diffuse through the slab material eventually.

The best thing you can do to protect slabs is to put them into ziplock bags with a sacrificial copper cent. Then put those bags in Tupperware-type containers and store at a constant, controlled temperature. Doing so will slow the diffusion process to a nearly undetectable level and your coins will never change in your lifetime.

IMO, all this fiddling around with inert gases is interesting conceptually but an exercise in futility. The major TPG slabs are essentially air tight but plastic is porous and trying to fight diffusion is impossible.