A rare political medal infected with tin pest.

BillJones

Tin pest is an old fashioned term collectors used for the corrosion that can form on white metal alloys that were used on tokens and medals. It is a blackish brown crustation that will eventually destroy the piece.

Collectors from my father’s generation told me that it is incurable. They said that you could not stop the stuff. I have found that you store the piece in climate controlled conditions at steady temperatures that it can be checked, but not reversed. The only “cure” is to scrape the offending metal off of the piece, but that gets to the dreaded term “tooling.”

Heritage held the DeWitt political items sale this weekend. I had hoped to buy a few items, but the prices were very strong. I did get the item I wanted most for about a $1,000 more than I thought it was worth and bought a second item that was okay. I will post information about them once I receive them.

One piece that really grabbed my attention was an example of a Zachary Taylor campaign piece, ZT 1848-1. It has been on my wish list for over 20 years. The piece offered was the plate medal from the DeWitt book. I was very sad to see that the tin pest had gotten much worse since the piece was photographed in the late 1950s.

IF this piece had been better, it would have been in the "live part" of the sale, but given the issues, it was in "robo section." I was still willing to spend $800 on it, but the final price, with the 25% buyers' fee was $3,850.

The only thing I'll say to the buyer is be careful. If you don't store this piece correctly, you will have a corroded disk of metal in a few years. It is my opinion that the university who held this collection did not store it properly, but that's my opinion.

fastfreddie

Interesting piece. Regarding corrosion I found this article most interesting on causes, preservation of all metals.

https://www.canada.ca/en/conservation-institute/services/preventive-conservation/guidelines-collections/metal-objects.html

EXOJUNKIE

Glad you were able to acquire a couple of items as prices in this sale were stratospheric … no “deals” that I am aware of … I could not compete. Look forward to seeing what you picked up!

ricko

@fastfreddie .... Thanks for that link. Very interesting resource. Cheers, RickO

Sapyx

Tin pest isn't "corrosion" in the usual sense of that word, being the tin is not reacting with something in the atmosphere. Rather, tin pest is caused by the spontaneous transformation of crystalline elemental tin into amorphous elemental tin. There isn't really a scientifically accurate analogous comparison to be made with any other everyday substance, but it's as if diamonds spontaneously turned into charcoal if you put them in the freezer. In short, tin pest is a physics problem, not a chemistry problem. Changing the chemical environment (eg. putting a tin coin in a slab or other well-sealed containment) will neither prevent tin pest from forming nor stop it spreading.

Tin pest happens when tin objects are stored at temperatures below 13 deg C (56 deg F); the colder it gets, the more likely that tin pest will start and spread; temperatures below -30 deg C (-22 deg F) are almost certainly going to see the transformation triggered, though it might take a year or so for the pest spots to become visible to the eye (which is why the apocryphal story of Napoleon's army freezing to death in the Russian winter, when the tin buttons on their uniforms disintegrated, is almost certainly a fabrication). Increasing the temperature again does not reverse the process, though will stop it from spreading. The only way to "cure" tin pest is to melt the tin back down again.

BLUEJAYWAY

Overall very interesting. Learned something new.

OldEastside

@BLUEJAYWAY said:
Overall very interesting. Learned something new.

I too have never heard of Tin Pest, Thanks Bill

Steve

johnny9434

That's a first for me as well. You never know when you'll learn something