Wash the pressure cooker and the lid inside and out with warm, soapy water. Dry the entire cooker thoroughly with the dish towel.
Fill the pot nearly full (up to 2 inches below the rim) of warm water and dissolve 2 tablespoons of the cream of tartar in the water.
Bring the water to a boil over high heat, reducing it to medium high once the water starts boiling. Allow the water to boil for at least 10 minutes or until the interior of the pot is no longer discolored.
Pour the water from the pan and allow the pan to cool enough to be handled. If there are stains remaining in the interior or on the exterior of the pan, use the steel wool pad to gently scrub them away. Take care not to scrub too aggressively.
Apply the silver polish to the exterior of the pressure cooker and the lid. Rub it on using a dry dishtowel or other soft cloth and follow the instructions on the packaging.