The process for machine-pressing bricks (‘soft-mud pressing’) is an extension of the mechanized process of ‘soft-mud moulding’, with the soft clay being mechanically pressed into the mould under uniform pressure rather than simply dropped in. Greater quantities of clay under higher pressure can be used to make heavier, denser and more weather-resistant bricks. Being made in a mould, such bricks are either solid or ‘frogged’ and, having been machine-pressed, have sharp edges, are regular in shape and are uniform in size.
Fig. 30 Frogged brick (facing).