After the liquor has been filtered and decolorized, thus completing the purification process, it is boiled under vacuum to crystallize out the sugar. The vacuum is essential, for it reduces the air pressure and lowers the boiling temperature, which allows the sugar to be crystallized without getting overheated and discolored. This process can take one to two hours and continues until the crystals grow to the desired size. During the process, an operator will pull samples out of the vacuum pans to check on the sugar crystals under a microscope.