Cleaning burnt glass bakeware can be a balancing act: You have to use enough force to remove any burned-on food or other stains while not scratching and permanently damaging the glass. Burned glass bakeware is not a lost cause; it just requires nonabrasive cleaners and a gentle yet persistent scrubbing method. The burned-on stains are easier to remove if you soften them with a liquid beforehand, plus it reduces the need for the rough scrubbing that could scratch the glass.
Position the burnt glass bakeware on a stove burner. Fill it with 1/2 cup vinegar and 2 cups warm water.
Set your stove heat to "medium high" and heat the vinegar and water mixture until it starts to lightly bubble. Let the mixture gently boil for at least five minutes to loosen any burned areas on the glass bakeware.
Turn off the heat and let the vinegar and water mixture cool down until it is safe to handle. Scrub at the burnt areas with a nylon or plastic scrubbing brush or pad.
Pour out the vinegar mixture carefully and examine it to see if any burnt areas remain on the glass. If so, pour 3 tbsp. baking soda and 4 cups warm water into your sink and stir the mixture together to evenly distribute the baking soda.
Place the burnt glass bakeware into the baking soda and water mixture. Let it soak in the mixture for at least five minutes, then scrub it gently with your scrubbing brush. Rinse the bakeware thoroughly with warm water, then repeat the entire process if any burned areas remain.