The reaction of solid calcium hydroxide with liquid or gaseous methanol, ethanol and toluene, and the effect this has on the surface properties of the solid was examined, as well as the modification of crystal habit by the presence of these molecules. The effect of the presence of acetate or propionate groups on crystal habit was examined. Reaction with methanol leads to the formation of methoxide groups. Reaction with toluene forms a surface complex, but also there is ingress of the molecules into slit-shaped pores. The presence of these solvents, or the inclusion of anions such as acetate groups during crystallization. can control the crystal habit of calcium hydroxide.