Create a mixture of 1 tablespoon mild liquid dish soap and 4 cups lukewarm water. Stir the water to incorporate the mild dish soap, which doesn’t contain dyes or perfumes.
Dampen a soft cloth with the soapy mixture and wipe down the concrete to remove any dust, dirt and debris from its surface. Wipe away the soapy solution with a separate damp cloth.
Dry the concrete countertop with a soft cloth. Fill in the superficial scratch with an acrylic single-component sealer. Using a fine-tipped paintbrush, preferably a spotter brush, spread the sealant inside the crack.
Wipe down the concrete around the crack with a soft cloth to remove any excess sealant. Allow the acrylic sealant to dry for at least 2 hours or according to the package directions.
Rub the newly filled crack gently with a fine-grit sandpaper to create a seamless finish. Wipe away the dust created by sanding with a tack cloth.