Tie a pen to the end of a thread wound clockwise around a spool. Pull the thread taut and move the pen counterclockwise to unwind the thread. The pen traces a curve approximated by an Archimedean spiral: The distance from the pen to the center of the spool is nearly proportional to the change in angle made by the thread relative to horizontal.
Printed on high-quality 170 gsm poster paper with a satin finish.
