Dick Johnson submitted these thoughts on a new term in the numismatic lexicon. -Editor Several mentions have been made in the blogs recently of a new term applied to the surface of Lincoln cents: woodgrain. The term is apt. The illustrated surface of an 1981-D cent does indeed look like the graining in wood.
While this may be considered an anomaly of toning, instead it is an anomaly of the metal composition. It is an error in mixing of copper and zinc. What you see on the surface are streaks of copper alternating with streaks of zinc. The metal in the blank is not one homogeneous mixture as it should be to form one uniform color; it exists even after rolling, blanking and striking. The surface shows this streaking.
The Denver Mint in 1981 was pushing through 5.37 billion cents in a year's time. Some shortcuts were taken whether the Mint was buying its strips from outside suppliers or formulating their own coinage metal and rolling it themselves. The metal did not get mixed properly to achieve that homogeneous (all alike) composition before any manufacturing process.
The formulation at the time was 19 parts copper to one part of zinc (this was a year before the copper coated zinc used for cent coinage since 1982). Mixing zinc and copper throughout is not easy and I have the greatest respect for those craftsmen and metalworkers who accomplish this.
The melting points are different -- zinc at 785 degrees Fahrenheit, copper at 1220 degrees F. If you are not careful the zinc can burn off before it is adequately mixed with molten copper. Takes a lot of skill. Streaks result from not thoroughly mixing the batter.
To read the blog article, see: 1981D woodgrain cent (http://www.cointalk.com/forum/t49005/)
Thanks again Dick, for another illuminating submission. I'll keep an eye out for one of these cents - interesting! -Editor
Wayne Homren, Editor
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