When a metal crystal is delivered and introduced into UHV, it carries with it a few manolayers of water and hydrocarbons that are adsorbed from ambient. Since carbon is bulk soluble in most metals to some degree, it is normally wise to initiate the preparation of a metal crystal by prolonged sputtering, i.e. several monolayer equivalents, followed by a stepwise, but gentle ramping up of the anneal temperature to prevent the carbon layer from diffusing into the bulk during annealing.