During one of our sessions in the woods we made solder by melting scraps of lead and tin together in an old frying pan and it made me think, what other metals could I make on a campfire? In this entry I will be exploring this.
Firstly, in order to find out what metals I could melt, it is important that I know the temperature of my fire. Wood fires can reach temperatures of up to 1000°C, however when we measured our campfire in the woods the highest we recorded was 500°C. given that we weren’t trying to make a really hot fire, I will take the halfway point, 750°C, as my fire temperature. I could possibly make my fire hotter using the right wood, and by using bellows to pump air into the fire, but I’m basing this on what I could realistically do in a forest school. Secondly, the vessel. We used an old frying pan which, while it worked, is not a very efficient vessel as much of the heat could radiate away without warming the metal much. I am going to assume that I am using a stainless steel stock pot with a lid. This will allow me to pile embers around my pot to allow maximum heat transfer without the worry of damaging my vessel.
With the preparations complete, let’s look at which metals we can melt! I’m going to assume that as a teacher I will have access to catalogues that will allow me to order supplies of these metals, failing that these are all available on the internet. According to the Jewelry Artists Network, at a temperature of 750°C I can melt: Aluminium (659°C); Lead (327°C); Tin (232°C) and Zinc (419°C). If I were to use charcoal I could reach temperatures of up to 2700°C, allowing me to melt most common metals, however I do not have the equipment needed to contain a fire of that temperature so I won’t. This does, however, explain why charcoal is still in use today by many blacksmiths and metal workers. Once I have my molten metal, what can I do with it? Well, when we made solder, one of the group was asked to make a mould out of clay into which we poured the solder to make a flower design. This could be done with children of any age, as long as they are kept safe during the pouring and cooling stages even nursery children could make metal shapes using moulds.
Having mentioned charcoal earlier, it is worth mentioning that charcoal pencils can easily be made during a session in the woods. This is done by taking a metal biscuit tin, making a hole in the top, and placing into it sticks which have been stripped of their bark. The tin is then placed in the fire for a couple of hours, and when it is removed and opened, you should have sticks of charcoal! The children can then take these back to the classroom and use them to draw with. As we saw in an earlier entry, when we burn wood with Oxygen we make Carbon Dioxide and water. When making charcoal, the wood is burned with very little oxygen, so the only by-products are Carbon, in the form of charcoal, and water.
I hope you found this interesting, and as always questions are very welcome!