RWB Posted November 27, 2020 Share Posted November 27, 2020 (edited) Old copper cents and half cents were actively withdrawn by the Mint Bureau following the Civil War. Here's a sample letter describing the value of the copper recovered. An obvious question is "Why didn't the Philadelphia Mint us the copper for alloy in silver and gold coins, or to make bronze cents?" The reason is that much recovered copper contained lead and other impurities which made it useless as silver and gold alloy. The Mint bought pure copper ingots from Baltimore for alloy purposes. A secondary issue was that the Treasury had accounted for profit when large coppers were made, and now needed appropriations from Congress to keep the books balanced and cover melting costs. A. Harnickell, Broker Lead, Copper, Tin, Spelter, etc No. 22 Cliff Street, New York September 7, 1874 Superintendent, U. S. Mint, Philadelphia Sir: I bid for the 10 tons more or less of copper ingots remelted from the old cent, 19cents per pound cash, removable at my own expense, Respectfully A. Harnickell Edited November 27, 2020 by RWB Fix formatting - as usual coinsandmedals 1 Link to comment Share on other sites More sharing options...
RWB Posted November 28, 2020 Author Share Posted November 28, 2020 RE: "The reason is that much recovered copper contained lead and other impurities which made it useless as silver and gold alloy." Explanation: Lead, antimony, bismuth, iron all made 0.900 fine gold and silver alloys brittle and difficult to roll to proper thickness without splitting and cracking. During the 1870s and 80s there were intermittent squabbles between the New York Assay Office, which refined a lot of precious metal used at the Philadelphia Mint, and the Mint's Melter & Refiner (Booth), and Coiner (Snowden). Defective ingots had to be reworked by M&R which wasted time and resources. The two factories prepared multiple agreements of cooperation from time to time, and then one or the other would "forget" about things and they would have the same disagreement again. RonnieR131 1 Link to comment Share on other sites More sharing options...
Just Bob Posted November 28, 2020 Share Posted November 28, 2020 Were these impurities hard to refine out of the copper at that time? Link to comment Share on other sites More sharing options...
Bignubnumismatics Posted November 28, 2020 Share Posted November 28, 2020 I don't think it was "hard" necessarily, just that it took far too much effort, time, and money for it to make any sense in repurposing the copper for use as alloy in the other denominations. Link to comment Share on other sites More sharing options...
RWB Posted November 28, 2020 Author Share Posted November 28, 2020 2 hours ago, Bignubnumismatics said: I don't think it was "hard" necessarily, just that it took far too much effort, time, and money for it to make any sense in repurposing the copper for use as alloy in the other denominations. Yep. Many businesses did only the minimum necessary to sell their product...if it didn't matter to the customer, it didn't matter to the producer. US Mint requirements for metal purity were more demanding than most, so they had to be very careful with the quality of metals they purchased. Their own refining was occasionally responsible for impurities. One of these involved NYAO using refining acid with a trace of selenium. The metal carried over into silver and made the metal brittle. Link to comment Share on other sites More sharing options...
Henri Charriere Posted November 28, 2020 Share Posted November 28, 2020 The melting points of gold and copper are 1948F and 1981F, respectively. That of lead (which I melted over my kitchen stove as a teenager when I didn't know better, oblivious to its poisonous fumes) is only 621F. So how difficult or inconvenient could it have been? We are talking about a 1:3 ratio, right? I am sure anyone interested in doing so would be far better equipped. Link to comment Share on other sites More sharing options...
Bignubnumismatics Posted November 28, 2020 Share Posted November 28, 2020 Dirt, and the equipment still wouldn't have made it cost-effective to do this. It wasn't just lead either, although most metals are lower than that of the copper and gold metals, Iron has a melting point of 2,800 degrees. Link to comment Share on other sites More sharing options...
RWB Posted November 28, 2020 Author Share Posted November 28, 2020 (edited) Impurities can be present within the alloy or as metallic salts, or individual metal crystals. A common example is the addition of zinc to a mixture of copper and nickel. This produces an alloy with lower melting temperature than just copper-nickel alloy. (Widely used in making die-struck counterfeit 3-cent and 5-cent coins.) In preparation copper and nickel are usually melted separately then thoroughly mixed, melted zinc at just below its vaporization temperature is added and quickly mixed, then the alloy is cast and cooled quickly. Remelting the Cu-Ni-Zn alloy is tricky due to volitization of zinc. The same applies to brass used for cartridge casings and was one reason the US Mints contracted "shell case copper" melting to specialty companies. Edited November 28, 2020 by RWB Link to comment Share on other sites More sharing options...
Hoghead515 Posted November 29, 2020 Share Posted November 29, 2020 Very interesting read RWB. I really enjoy history and those old hand written letters. Thank you very much for posting that. Link to comment Share on other sites More sharing options...
RWB Posted November 29, 2020 Author Share Posted November 29, 2020 4 hours ago, Hoghead515 said: Very interesting read RWB. I really enjoy history and those old hand written letters. Thank you very much for posting that. Look on the Newman Numismatic Portal site. You'll find a lot of manuscript letters and reports from the US Mint. Hoghead515 1 Link to comment Share on other sites More sharing options...
