Lime mortars require grinding to slake the unslaked particles and to make an intimate mixture of the materials. Lime/surkhi mortars are ground in two operations, first only the lime and surkhi are ground together and then sand is added and again ground. For big jobs grinding is done in a bullock-driven mortar mill (or machine). In a mortar-mill the diameter of the track should not be less than 8 m. No piece larger than 6 mm should be introduced in a mortar mill. For small jobs grinding can be done by ponding the ingredients in a small pit and mixing. Small quantities of mortar can be mixed by repeatedly turning over the materials with a shovel, and afterwards with a trowel, so as to mix them very thoroughly.