An evaporator for an ice making system comprising: a refrigerant conduit; and front and rear plates (14, 16) sandwiching the refrigerant conduit, each of the front and rear plates (14, 16) having: inner flat portions, each inner flat portion of the front plate facing, but being spaced from, a respective inner flat portion of the rear plate to define a respective spaced portion; a plurality of triangular fins dividing the respective plate (14, 16) into a plurality of ice forming columns; a set of first protrusions defined in the respective ice forming columns, each first protrusion on the front plate facing a respective first protrusion on the rear plate to define a respective active cavity, the refrigerant conduit extending through each of the active cavities; and a set of second protrusions defined in the respective ice forming columns, each second protrusion on the front plate facing a respective second protrusion on the rear plate to define a respective passive cavity, the refrigerant conduit not extending through any of the passive cavities; wherein the active and passive cavities (24, 26) are interspersed and separated by respective inner flat portions so as to define a plurality of ice forming sites in the ice forming columns of the respective plate (14, 16). a refrigerant conduit; and front and rear plates (14, 16) sandwiching the refrigerant conduit, each of the front and rear plates (14, 16) having: inner flat portions, each inner flat portion of the front plate facing, but being spaced from, a respective inner flat portion of the rear plate to define a respective spaced portion; a plurality of triangular fins dividing the respective plate (14, 16) into a plurality of ice forming columns; a set of first protrusions defined in the respective ice forming columns, each first protrusion on the front plate facing a respective first protrusion on the rear plate to define a respective active cavity, the refrigerant conduit extending through each of the active cavities; and a set of second protrusions defined in the respective ice forming columns, each second protrusion on the front plate facing a respective second protrusion on the rear plate to define a respective passive cavity, the refrigerant conduit not extending through any of the passive cavities; wherein the active and passive cavities (24, 26) are interspersed and separated by respective inner flat portions so as to define a plurality of ice forming sites in the ice forming columns of the respective plate (14, 16). inner flat portions, each inner flat portion of the front plate facing, but being spaced from, a respective inner flat portion of the rear plate to define a respective spaced portion; a plurality of triangular fins dividing the respective plate (14, 16) into a plurality of ice forming columns; a set of first protrusions defined in the respective ice forming columns, each first protrusion on the front plate facing a respective first protrusion on the rear plate to define a respective active cavity, the refrigerant conduit extending through each of the active cavities; and a set of second protrusions defined in the respective ice forming columns, each second protrusion on the front plate facing a respective second protrusion on the rear plate to define a respective passive cavity, the refrigerant conduit not extending through any of the passive cavities; wherein the active and passive cavities (24, 26) are interspersed and separated by respective inner flat portions so as to define a plurality of ice forming sites in the ice forming columns of the respective plate (14, 16).