The current study establishes the extent to which additive Ca 2+ ions impede the growth of CaCO 3 precipitates. More than 90% growth inhibition is achievable, depending on the concentration of additive Ca 2+ ions relative to the volume of precipitates. This study also highlights the critical importance of solution pH. It shows high growth inhibition is only achieved when additive Ca 2+ ions are present in high alkaline pH conditions.