What's going on here?

I noticed this happening to some of my coins. What is the foggy thing?


(click to enlarge the pictures)

Some background and more details:
- Coin was stored in the 2x2 for about 10-15 years.
- For about 3 of those years, the coins were in a non very friendly environment. High humidity, lots of dust.
- This is mainly happening to the BU coins.
- After taking the coin out, some of the substance stuck to the coin, but most of it remains in the plastic of the 2x2. (Picture 3)
- A soft wipe removed the substance from the coin and it looks BU again. (Picture 4)
- Pressing the plastic window against the coin, without opening the 2x2, makes the "fog" disappear.

 

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Condensation? Could be a change of temperature

 

It seems you have moisture infiltrating your coin storage area. Make sure your coins are dry before you store them. I put mine into a Ziplock bad and put the Ziplock bag into a Tupperware box before I store them.

 

It looks exactly like that, but it never dries. I first noticed after moving abroad and start re-organising my collection.

The coins were 100% dry before putting into the 2x2. I'm very careful about that.
Could it be some kind of mold? I guess from the time my collection was stored in that humid room.

Weird thing is that it didn't happen to all of them.

 

There's air already in the 2x2, and air can get into it via the cardboard (or even through the plastic). Air contains enough water to condense.

(It also couldn't be mould if it was completely dry).

You could store them in an airtight container with reusable silica gel packets.

 

I have some of that canned air like you use for computer keyboards and other dusty stuff. I like to use it to blow all the foreign material off a 2X2 before putting a coin in. Blow it off, let it dry, then put the coin in.

 

I use the Eva-Dry and they seem to work well and take about 12 hours to dry out when saturated. You just plug them into the wall outlet and the internal heater drives the moisture out of the dessicant (green when saturated, orange when dry).

But I've done some mind-experiments on alternate ways to preserve our coins from the deleterious effects of temperature, humidity, and atmospheric contaminants while still keeping them relatively accessible.

The first thought was a vacuum box but I rejected that. It's hard to build a box that will retain a vacuum, even a slight one and a vacuum leak will just draw in the surrounding atmosphere. Also, most people don't have access to a vacuum pump although most people have a vacuum cleaner that can be used in reverse to establish a small vacuum. Think about those pliofilm bags you see advertised to store your sweaters, etc. where you use a vacuum cleaner to remove the air. Still, while I could devise workarounds, vacuum doesn't seem to be the optimal solution.

But, what about the reverse of a slight vacuum which would be a slight pressure, say a few inches of water column, just enough to keep the environment out? So, if we build a box that will seal up tight against a few inches of internal pressure, provide a pressure gauge on the box and valved inlet and outlet connections, we can connect an inert nitrogen bottle and regulator. Then we can purge the air and moisture out of the box and then charge it with a few inches of pressure. A box like this could be constructed from plexiglass and fitted with a sealing lid. You could also use HDPE pipe material (not PVC!).

Anyway, just playing with the idea.

 

Burying them in an urn in the ground for 2000 years seems to do the trick. It might fail your accessibility test though. Perhaps you could set up a webcam to view them.

 

I was afraid was going to be PVC damage. I’ll check them all and change the affected holders.
2600+ to go

 

If you use the compressed air can to close to the coin it will leave a small amount of condensation on it. Make sure it is completely dry before you seal it.

 

Do not wipe or rub them in any way.