Phase diagram of alumina sol has been investigated, wherein a unique region of shear reversible gels has been discovered. In this region, rapid transformation from gel to sol was observed, where the viscosity shows a sudden drop by six orders of magnitude on application of shear stress. The sol to gel transformation was observed to depend on the composition of the sol and could be tuned in the range of few seconds to hours. These gels are suitable for fabricating complex three-dimensional structures using advanced technology of direct write and ink-jet printing.