The outcome and end product to this piece of work is unpredictable. Up to a certain point the teacher and pupils, won't be in control of the reactions that take place on the surface of the paper.
Target the theme of the lesson on the sun. Talk about what the sun is. For example, it is not just a yellow circle in the sky, but a torturous fireball. Explain how it is made up of bands of hot and warm colours, and that its surface isn't perfectly rounded, but shoots and spits out huge flames. Discuss what hot colours are. How do these colours make you feel? What do you think of when you look at reds, yellows and oranges?