Things You'll Need
Wide drywall knife
Spackle, or joint compound, is a pasty substance that drywall finishers use to cover seams and screw heads after a drywall installation. Finishers often store leftover spackle for future jobs. Typically, spackle keeps for about nine months. But sometimes mold begins to grow inside a bucket, making it unusable. The most effective way to prevent mold growth is to store it correctly. Manufacturer storage recommendations might vary slightly among different types of spackling products, but there are some general steps you can take to inhibit mold growth. Check the label for product-specific storage recommendations.
Use a wide drywall knife to scrape the inside of the bucket. Flick the spackle into the bottom of the container.
Wipe a damp cloth around the inside of the bucket above the spackle. Leave the interior and top edges as clean as possible. The goal is to make it hard for mold to cling to the slick, plastic sides, as well as to decrease the amount of dried spackle bits that could fall into the wet spackle.
Pour 1/2 inch of clean water into the pail.
Place the cover on the bucket and push it down firmly until you hear it snap. Sometimes spackle buckets are tough to close, so you may have to use your feet to tamp the edges down.
Store the bucket in a shady area, away from direct sunlight. Joint compound is fairly resilient, but you shouldn't store it in areas that experience extreme hot or cold temperatures. Roughly 50 to 65 degrees should be fine.
Pour out the water when you’re ready to use the joint compound. If you notice mold growing despite your best efforts, discard it.