My first project was about the propellers of ships: the really big ones that they use on supertankers. Sometimes they break and fall off when the ship is in the middle of the ocean – not nice! I was helping the manufacturers to improve the way they make these propellers so that they wouldn’t break. Big metal objects like this are often made by casting, which means they heat the metal up until it melts and pore the liquid metal into a mould. That’s pretty exciting to watch!