One of my favourite ways to sketch is to use bleach and ink. It may sound extreme and you must use it in a well ventilated area, but it can produce some of the most amazing effects. This is a good example of the technique. It is a sketch of some poppy seed heads I had dried from my back garden. It is drawn on tissue paper that had been glued down to my sketch book page. First outlining the shapes with pen and ink and then adding bold stripes of colour using the bleach and then a wash of ink.