The two main reasons that glass cooktops crack are hot spots caused by burnt-on food and scratches from the wrong cooking implements or harsh cleaners.
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Karinear 8400W 30 Inch Electric Cooktop 5 Burners Ceramic Cooktop, Drop-in Electric Radiant Cooktop with Front and Back Metal Frame, Child Lock, Timer, 220-240V, Hard Wire, No Plug : Appliances