The objects to be attained in gaging are to thoroughly incorporate the cement and sand, to evenly distribute the water throughout the mass, and, if possible, to give the mortar a certain tenacity resembling that of putty. This last object is not always possible of attainment with mortars containing a large dose of sand.
The ordinary method of preparing mortars in the laboratory is to gage with a trowel on a glass, slate, or marble slab. In gaging mortars, the cement and sand are first mixed dry; the materials are then drawn away from the center, leaving a crater to receive the water, which is all added at one time. The dry material is then gradually turned from the edges toward the center until all of the water is absorbed, after which the mass is thoroughly worked with the trowel in such a way as to rub the material between the trowel and plate until the consistency is uniform throughout. A batch of mortar sufficient for five briquets cannot usually be properly gaged by this method in less than five minutes.
The Committee of the American Society of Civil Engineers, in their preliminary report on methods of manipulation, suggested that "as soon as the water has been absorbed, which should not require more than one minute," the mortar should be kneaded with the hands for one and one-half minutes, the process being similar to that used in kneading dough.