Glass Cook Tops
Glass or ceramic cooktops are completely smooth and have the heating element underneath the heat resistant material. This keeps anything from spilling down under the burner, which would be difficult to clean. Because of the special surface type, glass cooktops require care when cleaning. It's recommended that you use nonabrasive cleaning products and every piece of cookware needs to be perfectly smooth on the bottom to avoid scratching the surface.
Cast-iron grill pans provide even heat and can withstand very high temperatures needed for searing and blackening food. However, cast iron is heavy and has a slightly irregular surface, which can lead to scratching on a glass cooktop. Nonstick-coated grill pans are lighter and typically smoother than cast iron, but the chemical compounds bonded to the metal pan cannot withstand as much heat, so the searing and blackening won't be as dramatic as with cast-iron grill pans.
Keeping any abrasive surface away from the glass cooktop is the only way to be sure that it won't be damaged by scratches. However, if you need to use something like a cast-iron grill pan, you can avoid scratches by not moving the pan around on the cook top. Instead of spinning or sliding the pan, lift it before moving to avoid scratching the surface.
Use metal heat diffusers between the cooktop and an abrasive grill pan to protect the cooktop. Placing a diffuser between the two will protect the glass of the range and still transmit heat reliably to the grill pan set on top. Heat diffusers are made of metals like aluminium, copper, steel and cast iron. Enameled cast iron is smoother than bare metal and reduces the likelihood of scratches on your glass.