FREEZER TO BOILING WATER
I saw this listed on DOC, and thought I'd give it a try. I really don't expect anything, and am afraid that the sudden temperature change may crack the coin. I understand the expand/contract rationale... but really don't expect anything. I guess we'll see.
Before
After 24 hours in the freezer, I threw them into boiling water for 5 minutes or so. I don't see all that much difference. Next, I am going to soak them in distilled water for 24 hours, then the freezer for 24 hours then boil them again. Perhaps distilled water will work into the dirt and increase the contraction/expansion.
Round 2
Some dirt has been removed, but it's minimal. I think regular dw soak would yield better results, so I'll label this as a minimal success.It didn't damage the coins, but didn't remove much dirt either.

 

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