The mechanism for carbon formation from hydrocarbons on transition metals, proposed 40 years ago, is reassessed, evaluating the role of surface catalysis and bulk diffusion. Under steady-state conditions, solid state reactions, which are essential to start-up the process, will be confined to carbon growth. The dynamics of carbon mass transfer is discussed, together with the thermodynamic equilibria prevailing at the metal-gas and metal-graphite interfaces. The reverse process of carbon gasification is also addressed. (C) 2011 Elsevier B. V. All rights reserved.