Inoculation of cast iron can take place in one or more of several stages: furnace, ladle, in-stream or in the mould. Inoculants are most effective immediately after they have been added to the cast iron. Over time, the effectiveness of the inoculant fades which reduces the nucleation potential of the iron.

Inoculating in the mould is the latest stage in the process where the iron can be inoculated. There is practically no fading of the effect of an in the mould inoculant and therefore a very low addition can be made, making in the mould inoculation an efficient method.