Retention of Plasticity
The length of time that mortar retains its plasticity is something of a trade-off. Plasticity should be retained long enough to allow the bricks to be laid, adjusted and a joint finish applied before the mortar dries out too much. This is more of a problem where very dry bricks are used, as they have a high suction rate. Alternatively, mortars that are excessively plasticized can be laid only to limited heights before the wall sinks and bed joints of the lower courses start to squeeze out.