Dust Formation around Wolf-Rayet Stars

We discuss the observational evidence in favour of dust formation around massive, evolved carbon-rich Wolf-Rayet stars. Large dust shells containing (amorphous carbon) grains are observed in persistent dust makers, such as the pinwheel system WR104 (WC9+OB) and periodic/episodic dust makers, such asWR140 (WC7+O) close to periastron. Problems with the nucleation and growth of dust in such harsh environments are discussed. It is probable that mixing of carbon-rich material from the WC star plus hydrogen from an OB companion, together with efficient shielding via the shocked region of their colliding winds, provides the necessary ingredients. Many problems with the nucleation and growth remain to be addressed. This revised version was published online in July 2006 with corrections to the Cover Date.