* KS3. Make some charcoal: collect twigs about 50mm long and 5mm in diameter; fill an old small can with them, and make a small hole in the top. Roast with a Bunsen burner - the smoke can also be burned (methane) - and after 15 minutes leave to cool. Open the can to find charcoal. Children can use it to draw their own cave pictures. Different trees produce different charcoals.
* KS4. Smelt metals by roasting copper and lead ores with charcoal on an old metal lid. Seeing beads of lead is quite magical, even in the fume cupboard. Challenge students to explain how this could be done on a bigger scale and without modern equipment.
* KS5. Students can research and use coloured pigments, such as red ochre (anhydrous iron oxide), chrome yellow, zinc oxide; mix the pigments with egg tempera (egg yolk) to create a simple paint to use for their own cave pictures. Better still, get them to make the compounds; Monastral blue is wonderful!