When you look down, some interesting (but probably dirty) things can be found. Walking along Brick Lane market one Sunday, I found a blue plastic container used to hold apples. I took it home and ironed it. (This was during my phase where I loved ironing plastic). About a month later I found the sheet in a sketchbook and studied it to find that letters where hidden in the melted parts.
I held the sheet up to the window and spotted every letter of the alphabet then took a photograph of it. Some printing, tracing, drawing and scanning later, a had a full alphabet of these plastic letters.