Abstract: Disclosed is a method of producing sodium hydroxide comprising the steps of: (a contacting trona ore and sodium hydroxide under conditions suitable to form sodium carbonate; (b) removing essentially all solids larger than 32 mesh from the sodium carbonate product of step (a); (c) contacting the sodium carbonate product of step (b) and calcium hydroxide in the presence of a suitable amount of seed crystal calcium carbonate with crystal size in the range of about 1 to about 10 microns, and under conditions suitable to form aqueous sodium hydroxide and calcium carbonate crystals with crystal size in the range of about 30 to about 50 microns; and (d) recovering aqueous NaOH from the reaction product of step (c). The seed crystals may be introduced from an external source, or made insitu in the lime slaker by the addition of a small amount of sodium carbonate into the lime slaker.