Protected Proofs Forever (Virtually)

The vast majority of my coins are in whitman Classic Albums. Many, many also in 2x2's or plastic rolls. Way, way back I started putting the Albums in plastic bags. Some coins and Albums I have had for well over 60 years. No zip lock type back then. I push out as much air as possible. No coins have toned, hazed, discolored in all this time. No air tights, no special nothing. Just a plastic bag with air pushed out.

Removing air, which is where sulphur is carried, would do a lot towards preventing tarnish.

Deterioration often comes from unexpected sources. For years, manufacturers insisted that you needed to put comic books in mylar holders, because polypropylene would yellow. I put a box of comics in PP away for about ten years. Some of the bags were yellowed, some not. since the bags were identical, it came down to the paper of the comics. Those printed on cheap newspaper yellowed the bags, while the high quality white paper ones, with less acid in the paper, didn't.

If you put a typical newspaper in the sunlight, it will turn brown in a week. I had a civil war paper in a cheap plastic bag on a piece of corrugated cardboard, and it was still white! Why? Before around 1890, papers were printed on paper with high rag content. Modern paper comes from highly acidic wood pulp.

Just cutting off air doesn't solve everything. Comic preservationists figured putting books in mylar and sealing them would prevent yellowing. Instead, the acid already in the paper outgassed into the bag and back into the book, and they aged faster than sitting them on the counter. The solution was to first deacidify each page and include a pH buffer, put them in mylar, vacuum out the air, then fill the bag with inert nitrogen before sealing.

Which brings us back to coins. To be really safe for multi-decade storage (time capsule stuff) you'd want to put them in something you could suck the air out of and fill with nitrogen.

Many gas stations are now putting nitrogen in tires. It's not expensive, and fills better than air because the larger molecules are less likely to leak.

A vacuum is an unnatural state and it will seek to come to equalibrium with the environment. Vacuum storage is fine for the short term, especially in a freezer. However, over time, all vacuums will leak and the net effect will be to draw in air.

This thread is worthy of a bump for some of the questions I'm seeing today.