Making Coins
Making coins requires shaping metal to the form of a die or pattern. In early times this was done by taking the die and hammering it onto a sheet of metal. In this set of explorations students will explore some of these simple techniques and learn something about different metal's malleability. Depending on the materials they might find, they can create a "coin" collection.
Materials Required
• Soft Pencil and paper
• Scissors
• Aluminum foil
• Soda can, hammer, piece of wood
• Optional (copper foil and stick--craft store item)
Paper Coins
The simplest method to make a coin is to rub a soft pencil on paper placed over the coin.
Foil Coins
Aluminum foil can be placed over a coin and your finger can press the image.
Aluminum Coins
Cut a square of aluminum from a soda can with a pair of scissors. Place the coin on the concrete floor. Put the aluminum over the coin. Place a piece of wood over the metal and coin and hit with a hammer several times.
Copper Coins
If you have access to a small piece of copper sheet you can mold a coin by using a small wooded dowel to press the copper against a coin placed underneath the sheet. It's similar to making a paper rubbing but requires more pressure.
Discussion
Different metals have been used to make coins. Silver, gold and copper were used early on as these metals were both precious and they were easy to shape. The ability of a metal to bend or mold is called malleability or ductility.
Examine this table below:
On this list, gold is the most ductile. It can be made so thin that it can be used to cover objects.
At the other end of the scale are Carbon and Beryllium. These metals have almost no ability to stretch. Instead, they crumble when hammered or pressed.
Question1. The metals that are most malleable/ductile are easy to mold or press as coins. Why do we not use these metals today? Why do we not use lead?
Question 2. The further you go down on the list above, the harder the metal. Why weren't these used in early coins?
Question 3. There are several reasons why many of these metals are not used in coins: a) too expensive or rare, b) too soft so it wears away too easily, c) poisonous or radioactive, d) too hard and not moldable, e) corrode too easily. Do a little research to see why many of the metals on the list would be eliminated from coin-making. What metals are left?
The manufacture of coins has an interesting history. An overview of the technology can be found here: http://muzeydeneg.ru/eng/?p=695