In a method of decalcification of purified sugar factory juices from a sugar factory process the juices, containing calcium ions, are sent onto an Na+ or K+ form strongly cationic ion exchange resin where the calcium ions are replaced with sodium and/or potassium ions. The ion exchange resin is then subject to regeneration (or washing) with dilute molasses. In a first variant of the method, the molasses is sent to the ion exchange resin in a cocurrent configuration. In a second variant, the molasses is sent to the ion exchange resin in a countercurrent configuration. This method can be used in a process to manufacture sugar from sugar beet or sugar cane.