Depending on the hardness of the water in your area, small spots may appear on the heating element of your kettle when you use it. This phenomenon is the result of scale build-up on the heating element and on the inside of the kettle over time. The harder the water, the faster scale builds up. Scale can occur in different colours. Although scale is harmless, too much scale can influence the performance of your kettle. Descale your kettle regularly. Best is to descale every month if you live in a hard water district and every three months if you live in a soft water district. (Also see question: 'How can I descale/clean the kettle?'