How are marbles made?
I saw it being done on TV. The marbles are originally small slices cut from long strips of melted glass – the whirl in the middle is because they make a sandwich of thin coloured glass strips between two fatter clear strips. At a certain temperature the glass is flexible and cuttable like toffee. So they cut little slices off the strips and drop them onto spinning metal rolls which capture the glass cubes and turn them into spheres by spinning them round and round, while keeping them in the same place. It’s a bit like making a ball of plasticine by rolling between your fingers, but perfectly and quickly with robotic metal rollers. The heat is off at this point so the glass solidifies in a marble shape while spinning. You can occasionally see a little of the cutting off point at one end of the marble.
