How To "Tone" Your Coins

LOL. Make SURE you post pics of those!

Probably a normal reaction of dissimilar metals touching each other. In metalurgy it is a known fact that any two different metals touching each other create an electrical charge during any change in temperature. It is really miniscue and seldom noticed by the average or normal measuring devises, but there non the less. It is the pricipal used in numerous industries for thermocouple wire systems of temperature measurements. An example is a small hole or indentation is made in an air duct or pipe, inserted with a threaded item and secured in place. A thermocouple head is screwed into that, two dissimilar metalic wires such as Cromel and Alumal are connected at that location and the other end to a sensitive gauge. Any change in temperature creats an electical charge and the gauge records that.
Back to the coins in Aluminum. If these coins were placed in a location where temperatures varied repeatedly, such small electrical charges were created. With the possibility of moisture or other gasses in the air, these may have been forced electronically to create toning on the coins as noted.
PS: Power station companies do studies of the ground prior to the construction of a power station for gradients and the possibility of high Aluminum contents. This is due to the usage of Copper Grounding wire systems. If there is large amounts of Aluminum in the soil, the Copper Ground wires will dissipate through electrical charges and combine with substances in the soil.
A recent board plant company found this to be true in Pennsyvania and had to switch to Stainless Steel for grounding.

Carl is a smart man. I follow his lead:

Two dissimilar metals in contact will create a micro-galvanic cell. The rate of electron flow between the metals will vary with temperature. Also, storage in just wrapped aluminum will not be air tight, so gases and moisture will move in and out throughout storage.

As time passes, the coin will preferentially absorb compounds onto the surface, depending on the polarity of the gases and the micro-charge state of the coin.

It's an interesting trick that could definately stimulate toning.

--which explains that "special feeling" if you ever chew a bit of food w/aluminum foil, and it touches a dental filling.

They're not in the OGP anymore. The coins were raw, wrapped in aluminum foil with a scrap of paper marked 1964 Mint Set

Easy, sure, but if your grandfather wrapped them up when they were new back in 1964, then it's not exactly rapid. 40 years is a bit too long for most AT doctors to wait.

If some kind of galvanic reaction has taken place, you'd expect to see some damage on the foil. Did the foil still look intact, or was it starting to turn white and crumbly?

Use soft Aluminum? Use scratchless foil? Wrap, don't rub? Coat each coin with liquid plastic first? Use Aluminum coins only?

We went on vacation at Mammoth Lakes in the California Sierra Nevada. There is a popular hot springs bathing area and we all went for a hot, sulfur-smelling swim. Afterwards my sister discovered that her sterling silver jewelry had turned a bright purple color.

There's another geology-theme AT option for you, Kurt!