Abstract: This invention pertains to a low head semi-continuous vacuum pan system for crystallization of a substance from solution of the substance, including the crystallization of a sugar from a sugar solution, that includes a sequential array of individual vacuum pans, wherein each pan has an associated discharge volume and the array is formed by positioning each pan so that its discharge volume is greater than the discharge volume of the immediately preceding pan and wherein heat and top-up solution are supplied to each pan and periodically all the contents of each pan are transferred to an immediately following pan and wherein controls are used to insure that the transfer takes place when the volume of each pan's contents reaches its associated discharge volume and the controls preferably ensure that each pan is empty before it receives the contents of the immediately preceding pan. This invention also pertains to a method of crystallizing a substance from a solution of the substance.