Removing old grease stains from napkins requires a specific method. First, you should pre-treat the stain with a grease-fighting dish soap. Apply a few drops of the soap directly to the stain and gently rub it into the fabric using your fingers. Let it sit for about 15 minutes to allow the soap to penetrate and break down the grease. After pre-treatment, wash the napkin as usual but use the hottest water setting that is safe for the fabric. Check the care label for guidance. If the stain is still visible after washing, repeat the process. Remember not to dry the napkin until the stain is completely gone, as heat can set the stain, making it more difficult to remove.