The puddling process began to be displaced with the introduction of the Bessemer process, which produced steel. This could be converted into wrought iron using the Aston process for a fraction of the cost and time. For comparison, an average size charge for a puddling furnace was while a Bessemer converter charge was (13,600 kg). The puddling process could not be scaled up, being limited by the amount that the puddler could handle. It could only be expanded by building more furnaces.