Cover the iodine stain in your car with talcum powder. Leave the talcum powder on the upholstery for 20 minutes to absorb excess moisture. Vacuum the upholstery to remove the powder.
Place 1 tablespoon of dish detergent in a bowl. Add 2 cups of cool water and stir.
Moisten a sponge with the diluted detergent solution. Squeeze the sponge to remove excess liquid.
Sponge your iodine-stained upholstery with the detergent solution until the stain is moist. Allow the solution to remain on the car upholstery for 30 minutes.
Dampen a clean cloth with cool water. Press the cloth against the iodine stain before blotting it with a dry cloth. Repeatedly alternate sponging the stain with damp cloth and a dry one to lift as much of the stain as possible.
Treat any remaining iodine stain on your car upholstery with a mixture made from 1 tablespoon sodium thiosulfate and 1 cup of cool water. Dab the stain with the solution before applying 3 drops of ammonia to the stain with an eyedropper.
Press a dry cloth into the upholstery to absorb the stain. Rinse the upholstery by blotting it with a damp cloth. Dry the surface with another cloth. Allow the upholstery to air-dry completely.