CAUTION: Thermite is almost impossible to extinguish once ignited, do not do this anywhere near your house or valuables. I do not recommend anyone do this unless you know what you’re doing.
Thermite is the stuff of legends, everyone knows what it is but few know how to make it. Well it’s simple; all you need are empty aluminium cans and rust. No seriously, that’s all it is.
NOTE: If you’re lazy you can buy aluminium powder and iron oxide from eBay no questions asked, but as usual this is about science not convenience.
Using a coffee grinder shred your aluminium cans into a fine powder, the smaller the grains the better. If you have an old etch-a-sketch you can crack that open and collect the dust, it is pure aluminium powder.
Collect rust from anything rusty, you can make your own by soaking iron nails in a weak solution of brine. You can make it a fine powder by using the coffee grinder method.
The proportions need to be correct for this to work. Mix 3 parts aluminium to 8 parts rust (by weight). You can mix by volume too but due to inconsistencies in particle size it may not be accurate, but the mixture is usually 50-50 by volume.
To light it, use a sparkler or strip of magnesium as a fuse, stand well back and enjoy.
Chemical equation: Fe2O3 + 2Al => 2Fe + Al2O3