Stains/iridescence have appeared on the glass.

Generally, the stains and iridescence that appear on the ceramic glass are grease residues that have been burned on its surface. Cleaning should be done using a clean, damp cloth with soap (preferably a special product for ceramic glass). Let the product sit for a certain time and then remove the dirt by rubbing with the cloth.

Stubborn dirt can be removed with a synthetic fiber pad or with the help of a glass scraper. NEVER with metal espartos, chemical or abrasive products.