jonab 1,644 Posted October 24, 2018 Report Share Posted October 24, 2018 I found an ancient Roman coin once in the garden of our house in Hucknall. I took it to school to show it off and decided that it would look better if it was cleaned up. I sneaked into the science labs, got hold of some nitric acid and duly dipped the coin into the acid. With amazing rapidity, the coin fizzed, hissed and gave off clouds of brown fumes and then completely disappeared, leaving behind a blue liquid. Lesson learned: copper is soluble in nitric acid with the formation of nitrogen dioxide fumes and blue copper nitrate. 1 1 Quote Link to post Share on other sites
FLY2 10,108 Posted October 24, 2018 Report Share Posted October 24, 2018 I always use a blob of either HP sauce, or Heinz Tomato Ketchup to clean dirty coins. Leave inserted for a few hours, and after a quick rinse, hey presto ! 1 Quote Link to post Share on other sites
Jill Sparrow 10,307 Posted October 24, 2018 Report Share Posted October 24, 2018 What's the cleaning agent in those, FLY? Vinegar? Quote Link to post Share on other sites
FLY2 10,108 Posted October 24, 2018 Report Share Posted October 24, 2018 I think so Jill. Years ago, I just soaked them in vinegar, but I think the sauces are more effective, and doesn't smell. Quote Link to post Share on other sites
jonab 1,644 Posted October 24, 2018 Report Share Posted October 24, 2018 One of the best things for cleaning copper and brass is cream of tartar (potassium hydrogen tartrate) which you can buy from good grocers shops (used in homemade baking powder). Mix to a paste with water and lightly rub the article being cleaned. It is very mildly abrasive (much less so than Brasso) and the tarnish dissolves in the watery part. Quote Link to post Share on other sites
AfferGorritt 868 Posted October 24, 2018 Author Report Share Posted October 24, 2018 Half the fun was researching and cleaning, although the cleaning needed to be done very carefully. I once decided to experiment with a home-made electrolysis set-up. Old phone charger, stainless steel spoon and a salt/lemon juice solution for the electrolyte. Completely fried a George III halfpenny! Very clean, though! 1 Quote Link to post Share on other sites
AfferGorritt 868 Posted October 26, 2018 Author Report Share Posted October 26, 2018 Another one of my bits. This is a George III "cartwheel" penny, so called because of its size and wide rim. It was the first copper coin, the first to be made by mechanical means (rather than by a guy with a die and hammer) and only minted for one year, 1797, because people were fed up with its size and weight. In fact the two penny piece minted in the same year was bigger and heavier! You wouldn't want a pocket full of these! Had to photograph it in a strong side light to show the little detail left. 3 Quote Link to post Share on other sites
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