flour mixture employed other slurry additions are required a wetting agent to ensure proper wetting of the wax pattern by the slurry i prefer a non ionic wetting agent since these are compatable with the binder colloidal silica employed these agents are readily available commercially also a defoaming agent may be required if excessive foam is noted on the slurry during the mixing operation if good slurry mixing practices are followed foaming will not be a serious problem i have employed antifoam 60 manufactured by the general electric company in the amounts of 0 005 by weight to 0 008 by weight of the slurry directly to the slurry i have found 8cc to 12cc of wetting agent per 100 lbs total weight of the slurry will induce good wetting properties to the slurry the following flour mixtures have been employed and yield satisfactory primary slurries all percentages are by weight percent and all flours are fused alumina u s standard sieve size acid washed ______________________________________mix no 1 mix no 6 240 mesh 50 240 mesh 65 400 mesh 50 320 mesh 35 mix no 2 mix no 7 240 mesh 66 240 mesh 85 320 mesh 34 400 mesh 15 mix no 3 mix no 8 240 mesh 50 240 mesh 70 320 mesh 50.