Lay the white cotton dress on a flat work surface. Cover the entire black ink stain with cornstarch. Leave the cornstarch on for 10 minutes to absorb any excess moisture from the ink.
Shake the cornstarch off of the dress and into the garbage. Pour rubbing alcohol onto a sponge and blot the ink stain with it. As the ink lifts, move to a clean portion of the sponge. Allow the rubbing alcohol to dry completely.
Add 2 tbsp. of white distilled vinegar in a bowl then mix in 3 tbsp. of cornstarch. Apply the paste to the ink stain and let it dry.
Brush off the cornstarch paste. Drizzle heavy-duty laundry detergent over the black ink stain to cover it.
Pour 3 tbsp. of ammonia into a bucket and add 1 qt. of warm water. Place the white cotton dress with the detergent still on it into the ammonia solution. Allow the dress to soak for 30 minutes.
Rinse the cotton fabric thoroughly with cool water to remove the loosened ink and the ammonia solution.
Launder the white cotton dress in warm water. Use heavy-duty laundry detergent and chlorine bleach to remove any last traces of the ink stain. Check the dress, before drying it, to make sure the entire stain is gone. Treat any remaining ink stain by soaking the dress in 1/4-cup of bleach mixed with 1 gallon of warm water for 30 minutes then wash the dress again.