As soon as any plastic, aluminium foil or sugar melts onto the hot cooking zone, use a glass ceramic scraper immediately to remove its tough residue so that it does not burn* onto the cooktop.     * Changes in the colour of the cooktop are the result of residues that have not been removed and have burnt on. Glossy spots are the result of wear by the pan base, especially if aluminium-based cookware or unsuitable cleaning agents are used.