(One particular brand is Chimney RX Brushable Crown Repair; offered with the gallon at saversystems.com) Deal with your entire crown then smooth it with a paintbrush (Image 2). Wait around till the sealer dries tacky to the touch, then utilize a 2nd coat with a brush. Clean up with water. https://fireplace78853.verybigblog.com/27757147/direct-vent-gas-fireplace-fundamentals-explained