Whether you hollow out a gourd and use it as a bird feeder or you leave it intact and paint or stain it, you must properly clean gourds prior to using them for anything. Take special precautions to remove any black mold growing on the outside of the gourd, and then preserve and decorate the gourd for years of enjoyment.
Wait until the gourd is completely dry inside. To determine if a gourd is dry enough for cleaning, shake it vigorously. If you hear seeds rattling inside the gourd, this indicates that it is dry inside. A dried gourd is also quite light and it will sound hollow inside when you rap on the outer shell.
Fill a bucket with warm water and add enough dish soap to create soapy water. Place the gourd into the soapy water, and scrub at the outside of the gourd with the kitchen scrubber. If there are stubborn spots of mold or blemishes on the gourd, scrape them off with the dull edge of the butter knife. Wash the gourd until the outer surface is free of blemishes and mold.
Remove stubborn mold by washing the gourd in a bleach solution. Fill the bucket with 1 part bleach and 10 parts warm water. Scrub at the moldy surface with the plastic kitchen scrubber to remove the mold. Rinse the gourd well.
Allow the gourd to dry completely to assess the condition of the outer surface before proceeding with any other cleaning techniques.
Consider using sandpaper to clean the outer surface if you will be painting the gourd. Using sandpaper will leave fine scratches on the surface of the gourd. Paint will cover these scratches, but stain or dye will not. Rub the sandpaper lightly over the surface to work at mold spots. Using sandpaper will also help to create a smooth outer surface. Wipe the gourd with a damp cloth to remove any dust.