281. Having decided upon the proportions of cement, sand and water, it remains to incorporate these into a plastic, homogeneous mass. The size of the batch should be so adjusted, if possible, that a full barrel of cement shall be used, and for careful work the amount of sand should be weighed instead of measured. Where this is impracticable, the condition of the sand from day to day, as regards the amount of moisture contained, should be taken into account (see §§ 262 and 263).

Mortar is usually mixed by hand, but where large amounts are to be used, machine mixers may profitably be introduced.